# FOSS Project Spotlight: LinuxBoot (Linux Journal)

Post Syndicated from jake original https://lwn.net/Articles/747380/rss

Linux Journal takes a look at the newly announced LinuxBoot project. LWN covered a related talk back in November. “Modern firmware generally consists of two main parts: hardware initialization (early stages) and OS loading (late stages). These parts may be divided further depending on the implementation, but the overall flow is similar across boot firmware. The late stages have gained many capabilities over the years and often have an environment with drivers, utilities, a shell, a graphical menu (sometimes with 3D animations) and much more. Runtime components may remain resident and active after firmware exits. Firmware, which used to fit in an 8 KiB ROM, now contains an OS used to boot another OS and doesn’t always stop running after the OS boots. LinuxBoot replaces the late stages with a Linux kernel and initramfs, which are used to load and execute the next stage, whatever it may be and wherever it may come from. The Linux kernel included in LinuxBoot is called the ‘boot kernel’ to distinguish it from the ‘target kernel’ that is to be booted and may be something other than Linux.

# Hacker House’s Zero W–powered automated gardener

Post Syndicated from Alex Bate original https://www.raspberrypi.org/blog/hacker-house-automated-gardener/

Are the plants in your home or office looking somewhat neglected? Then build an automated gardener using a Raspberry Pi Zero W, with help from the team at Hacker House.

#### Make a Raspberry Pi Automated Gardener

See how we built it, including our materials, code, and supplemental instructions, on Hackster.io: https://www.hackster.io/hackerhouse/automated-indoor-gardener-a90907 With how busy our lives are, it’s sometimes easy to forget to pay a little attention to your thirsty indoor plants until it’s too late and you are left with a crusty pile of yellow carcasses.

## Building an automated gardener

Tired of their plants looking a little too ‘crispy’, Hacker House have created an automated gardener using a Raspberry Pi Zero W alongside some 3D-printed parts, a 5v USB grow light, and a peristaltic pump.

They designed and 3D printed a PLA casing for the project, allowing enough space within for the Raspberry Pi Zero W, the pump, and the added electronics including soldered wiring and two N-channel power MOSFETs. The MOSFETs serve to switch the light and the pump on and off.

Due to the amount of power the light and pump need, the team replaced the Pi’s standard micro USB power supply with a 12v switching supply.

## Coding an automated gardener

All the code for the project — a fairly basic Python script —is on the Hacker House GitHub repository. To fit it to your requirements, you may need to edit a few lines of the code, and Hacker House provides information on how to do this. You can also find more details of the build on the hackster.io project page.

While the project runs with preset timings, there’s no reason why you couldn’t upgrade it to be app-based, for example to set a watering schedule when you’re away on holiday.

To see more for the Hacker House team, be sure to follow them on YouTube. You can also check out some of their previous Raspberry Pi projects featured on our blog, such as the smartphone-connected door lock and gesture-controlled holographic visualiser.

## Raspberry Pi and your home garden

Raspberry Pis make great babysitters for your favourite plants, both inside and outside your home. Here at Pi Towers, we have Bert, our Slack- and Twitter-connected potted plant who reminds us when he’s thirsty and in need of water.

I’m good. There’s plenty to drink!

And outside of the office, we’ve seen plenty of your vegetation-focused projects using Raspberry Pi for planting, monitoring or, well, commenting on social and political events within the media.

If you use a Raspberry Pi within your home gardening projects, we’d love to see how you’ve done it. So be sure to share a link with us either in the comments below, or via our social media channels.

The post Hacker House’s Zero W–powered automated gardener appeared first on Raspberry Pi.

# New – Encryption at Rest for DynamoDB

Post Syndicated from Jeff Barr original https://aws.amazon.com/blogs/aws/new-encryption-at-rest-for-dynamodb/

At AWS re:Invent 2017, Werner encouraged his audience to “Dance like nobody is watching, and to encrypt like everyone is:

The AWS team is always eager to add features that make it easier for you to protect your sensitive data and to help you to achieve your compliance objectives. For example, in 2017 we launched encryption at rest for SQS and EFS, additional encryption options for S3, and server-side encryption of Kinesis Data Streams.

Today we are giving you another data protection option with the introduction of encryption at rest for Amazon DynamoDB. You simply enable encryption when you create a new table and DynamoDB takes care of the rest. Your data (tables, local secondary indexes, and global secondary indexes) will be encrypted using AES-256 and a service-default AWS Key Management Service (KMS) key. The encryption adds no storage overhead and is completely transparent; you can insert, query, scan, and delete items as before. The team did not observe any changes in latency after enabling encryption and running several different workloads on an encrypted DynamoDB table.

Creating an Encrypted Table
You can create an encrypted table from the AWS Management Console, API (CreateTable), or CLI (create-table). I’ll use the console! I enter the name and set up the primary key as usual:

Before proceeding, I uncheck Use default settings, scroll down to the Encrypytion section, and check Enable encryption. Then I click Create and my table is created in encrypted form:

I can see the encryption setting for the table at a glance:

When my compliance team asks me to show them how DynamoDB uses the key to encrypt the data, I can create a AWS CloudTrail trail, insert an item, and then scan the table to see the calls to the AWS KMS API. Here’s an extract from the trail:

{
"eventTime": "2018-01-24T00:06:34Z",
"eventSource": "kms.amazonaws.com",
"eventName": "Decrypt",
"awsRegion": "us-west-2",
"userAgent": "dynamodb.amazonaws.com",
"requestParameters": {
"encryptionContext": {
"aws:dynamodb:tableName": "reg-users",
"aws:dynamodb:subscriberId": "1234567890"
}
},
"responseElements": null,
"requestID": "7072def1-009a-11e8-9ab9-4504c26bd391",
"eventID": "3698678a-d04e-48c7-96f2-3d734c5c7903",
"resources": [
{
"ARN": "arn:aws:kms:us-west-2:1234567890:key/e7bd721d-37f3-4acd-bec5-4d08c765f9f5",
"accountId": "1234567890",
"type": "AWS::KMS::Key"
}
]
}


Available Now
This feature is available now in the US East (N. Virginia), US East (Ohio), US West (Oregon), and EU (Ireland) Regions and you can start using it today.

There’s no charge for the encryption; you will be charged for the calls that DynamoDB makes to AWS KMS on your behalf.

Jeff;

# HackSpace magazine 3: Scrap Heap Hacking

Post Syndicated from Andrew Gregory original https://www.raspberrypi.org/blog/hackspace-magazine-3-scrap-heap-hacking/

We’re making with a purpose in issue 3 of HackSpace magazine. Not only are we discovering ways in which 3D printing is helping to save resources — and in some case lives — in the developing world, we’re also going all out with recycling. While others might be content with separating their glass and plastic waste, we’re going much, much further by making useful things out of discarded old bits of rubbish you can find at your local scrapyard.

## Hackspaces

We’re going to Cheltenham Hackspace to learn how to make a leather belt, to Liverpool to discover the ways in which an open-source design and some bits and bobs from IKEA are protecting our food supply, and we also take a peek through the doors of Nottingham Hackspace.

## Tutorials

The new issue also has the most tutorials you’ll have seen anywhere since…well, since HackSpace magazine issue 2! Guides to 3D-printing on fabric, Arduino programming, and ESP8266 hacking are all to be found in issue 3. Plus, we’ve come up with yet another way to pipe numbers from the internet into big, red, glowing boxes — it’s what LEDs were made for.

With the addition of racing drones, an angry reindeer, and an intelligent toaster, we think we’ve definitely put together an issue you’ll enjoy.

The physical copy of HackSpace magazine is available at all good UK newsagents today, and you can order it online from the Raspberry Pi Press store wherever you are based. Moreover, you can download the free PDF version from our website. And if you’ve read our first two issues and enjoyed what you’ve seen, be sure to subscribe!

## Write for us

Are you working on a cool project? Do you want to share your skills with the world, inspire others, and maybe show off a little? HackSpace magazine wants your article! Send an outline of your piece to us, and we’ll get back to you about including it in a future issue.

The post HackSpace magazine 3: Scrap Heap Hacking appeared first on Raspberry Pi.

# SUPER game night 3: GAMES MADE QUICK??? 2.0

Post Syndicated from Eevee original https://eev.ee/blog/2018/01/23/super-game-night-3-games-made-quick-2-0/

Game night continues with a smorgasbord of games from my recent game jam, GAMES MADE QUICK??? 2.0!

The idea was to make a game in only a week while watching AGDQ, as an alternative to doing absolutely nothing for a week while watching AGDQ. (I didn’t submit a game myself; I was chugging along on my Anise game, which isn’t finished yet.)

I can’t very well run a game jam and not play any of the games, so here’s some of them in no particular order! Enjoy!

These are impressions, not reviews. I try to avoid major/ending spoilers, but big plot points do tend to leave impressions.

## Weather Quest, by timlmul

short · rpg · jan 2017 · (lin)/mac/win · free on itch · jam entry

Weather Quest is its author’s first shipped game, written completely from scratch (the only vendored code is a micro OO base). It’s very short, but as someone who has also written LÖVE games completely from scratch, I can attest that producing something this game-like in a week is a fucking miracle. Bravo!

For reference, a week into my first foray, I think I was probably still writing my own Tiled importer like an idiot.

Only Mac and Windows builds are on itch, but it’s a LÖVE game, so Linux folks can just grab a zip from GitHub and throw that at love.

FINAL SCORE: ⛅☔☀

## Pancake Numbers Simulator, by AnorakThePrimordial

short · sim · jan 2017 · lin/mac/win · free on itch · jam entry

Given a stack of N pancakes (of all different sizes and in no particular order), the Nth pancake number is the most flips you could possibly need to sort the pancakes in order with the smallest on top. A “flip” is sticking a spatula under one of the pancakes and flipping the whole sub-stack over. There’s, ah, a video embedded on the game page with some visuals.

Anyway, this game lets you simulate sorting a stack via pancake flipping, which is surprisingly satisfying! I enjoy cleaning up little simulated messes, such as… incorrectly-sorted pancakes, I guess?

This probably doesn’t work too well as a simulator for solving the general problem — you’d have to find an optimal solution for every permutation of N pancakes to be sure you were right. But it’s a nice interactive illustration of the problem, and if you know the pancake number for your stack size of choice (which I wish the game told you — for seven pancakes, it’s 8), then trying to restore a stack in that many moves makes for a nice quick puzzle.

FINAL SCORE: $$\frac{18}{11}$$

## Framed Animals, by chridd

short · metroidvania · jan 2017 · web/win · free on itch · jam entry

The concept here was to kill the frames, save the animals, which is a delightfully literal riff on a long-running AGDQ/SGDQ donation incentive — people vote with their dollars to decide whether Super Metroid speedrunners go out of their way to free the critters who show you how to walljump and shinespark. Super Metroid didn’t have a showing at this year’s AGDQ, and so we have this game instead.

It’s rough, but clever, and I got really into it pretty quickly — each animal you save gives you a new ability (in true Metroid style), and you get to test that ability out by playing as the animal, with only that ability and no others, to get yourself back to the most recent save point.

I did, tragically, manage to get myself stuck near what I think was about to be the end of the game, so some of the animals will remain framed forever. What an unsatisfying conclusion.

Gravity feels a little high given the size of the screen, and like most tile-less platformers, there’s not really any way to gauge how high or long your jump is before you leap. But I’m only even nitpicking because I think this is a great idea and I hope the author really does keep working on it.

FINAL SCORE: 136,596.69 ## Battle 4 Glory, by Storyteller Games short · fighter · jan 2017 · win · free on itch · jam entry This is a Smash Bros-style brawler, complete with the four players, the 2D play area in a 3D world, and the random stage obstacles showing up. I do like the Smash style, despite not otherwise being a fan of fighting games, so it’s nice to see another game chase that aesthetic. Alas, that’s about as far as it got — which is pretty far for a week of work! I don’t know what more to say, though. The environments are neat, but unless I’m missing something, the only actions at your disposal are jumping and very weak melee attacks. I did have a good few minutes of fun fruitlessly mashing myself against the bumbling bots, as you can see. FINAL SCORE: 300% ## Icnaluferu Guild, Year Sixteen, by CHz short · adventure · jan 2017 · web · free on itch · jam entry Here we have the first of several games made with bitsy, a micro game making tool that basically only supports walking around, talking to people, and picking up items. I tell you this because I think half of my appreciation for this game is in the ways it wriggled against those limits to emulate a Zelda-like dungeon crawler. Everything in here is totally fake, and you can’t really understand just how fake unless you’ve tried to make something complicated with bitsy. It’s pretty good. The dialogue is entertaining (the rest of your party develops distinct personalities solely through oneliners, somehow), the riffs on standard dungeon fare are charming, and the Link’s Awakening-esque perspective walls around the edges of each room are fucking glorious. FINAL SCORE: 2 bits ## The Lonely Tapes, by JTHomeslice short · rpg · jan 2017 · web · free on itch · jam entry Another bitsy entry, this one sees you play as a Wal— sorry, a JogDawg, which has lost its cassette tapes and needs to go recover them! (A cassette tape is like a VHS, but for music.) (A VHS is—) I have the sneaking suspicion that I missed out on some musical in-jokes, due to being uncultured swine. I still enjoyed the game — it’s always clear when someone is passionate about the thing they’re writing about, and I could tell I was awash in that aura even if some of it went over my head. You know you’ve done good if someone from way outside your sphere shows up and still has a good time. FINAL SCORE: Nine… Inch Nails? They’re a band, right? God I don’t know write your own damn joke ## Pirate Kitty-Quest, by TheKoolestKid short · adventure · jan 2017 · win · free on itch · jam entry I completely forgot I’d even given “my birthday” and “my cat” as mostly-joking jam themes until I stumbled upon this incredible gem. I don’t think — let me just check here and — yeah no this person doesn’t even follow me on Twitter. I have no idea who they are? BUT THEY MADE A GAME ABOUT ANISE AS A PIRATE, LOOKING FOR TREASURE PIRATE. ANISE PIRATE ANISE!!! This game wins the jam, hands down. 🏆 FINAL SCORE: Yarr, eight pieces o’ eight ## CHIPS Mario, by NovaSquirrel short · platformer · jan 2017 · (lin/mac)/win · free on itch · jam entry You see this? This is fucking witchcraft. This game is made with MegaZeux. MegaZeux games look like THIS. Text-mode, bound to a grid, with two colors per cell. That’s all you get. Until now, apparently?? The game is a tech demo of “unbound” sprites, which can be drawn on top of the character grid without being aligned to it. And apparently have looser color restrictions. The collision is a little glitchy, which isn’t surprising for a MegaZeux platformer; I had some fun interactions with platforms a couple times. But hey, goddamn, it’s free-moving Mario, in MegaZeux, what the hell. (I’m looking at the most recently added games on DigitalMZX now, and I notice that not only is this game in the first slot, but NovaSquirrel’s MegaZeux entry for Strawberry Jam last February is still in the seventh slot. RIP, MegaZeux. I’m surprised a major feature like this was even added if the community has largely evaporated?) FINAL SCORE: n/a, disqualified for being probably summoned from the depths of Hell ## d!¢< pic, by 573 Games short · story · jan 2017 · web · free on itch · jam entry This is a short story about not sending dick pics. It’s very short, so I can’t say much without spoiling it, but: you are generally prompted to either text something reasonable, or send a dick pic. You should not send a dick pic. It’s a fascinating artifact, not because of the work itself, but because it’s so terse that I genuinely can’t tell what the author was even going for. And this is the kind of subject where the author was, surely, going for something. Right? But was it genuinely intended to be educational, or was it tongue-in-cheek about how some dudes still don’t get it? Or is it side-eying the player who clicks the obviously wrong option just for kicks, which is the same reason people do it for real? Or is it commentary on how “send a dick pic” is a literal option for every response in a real conversation, too, and it’s not that hard to just not do it — unless you are one of the kinds of people who just feels a compulsion to try everything, anything, just because you can? Or is it just a quick Twine and I am way too deep in this? God, just play the thing, it’s shorter than this paragraph. I’m also left wondering when it is appropriate to send a dick pic. Presumably there is a correct time? Hopefully the author will enter Strawberry Jam 2 to expound upon this. FINAL SCORE: 3½” 😉 ## Marble maze, by Shtille short · arcade · jan 2017 · win · free on itch · jam entry Ah, hm. So this is a maze navigated by rolling a marble around. You use WASD to move the marble, and you can also turn the camera with the arrow keys. The trouble is… the marble’s movement is always relative to the world, not the camera. That means if you turn the camera 30° and then try to move the marble, it’ll move at a 30° angle from your point of view. That makes navigating a maze, er, difficult. Camera-relative movement is the kind of thing I take so much for granted that I wouldn’t even think to do otherwise, and I think it’s valuable to look at surprising choices that violate fundamental conventions, so I’m trying to take this as a nudge out of my comfort zone. What could you design in an interesting way that used world-relative movement? Probably not the player, but maybe something else in the world, as long as you had strong landmarks? Hmm. FINAL SCORE: ᘔ ## Refactor: flight, by fluffy short · arcade · jan 2017 · lin/mac/win · free on itch · jam entry Refactor is a game album, which is rather a lot what it sounds like, and Flight is one of the tracks. Which makes this a single, I suppose. It’s one of those games where you move down an oddly-shaped tunnel trying not to hit the walls, but with some cute twists. Coins and gems hop up from the bottom of the screen in time with the music, and collecting them gives you points. Hitting a wall costs you some points and kills your momentum, but I don’t think outright losing is possible, which is great for me! Also, the monk cycles through several animal faces. I don’t know why, and it’s very good. One of those odd but memorable details that sits squarely on the intersection of abstract, mysterious, and a bit weird, and refuses to budge from that spot. The music is great too? Really chill all around. FINAL SCORE: 🎵🎵🎵🎵 ## The Adventures of Klyde short · adventure · jan 2017 · web · free on itch · jam entry Another bitsy game, this one starring a pig (humorously symbolized by a giant pig nose with ears) who must collect fruit and solve some puzzles. This is charmingly nostalgic for me — it reminds me of some standard fare in engines like MegaZeux, where the obvious things to do when presented with tiles and pickups were to make mazes. I don’t mean that in a bad way; the maze is the fundamental environmental obstacle. A couple places in here felt like invisible teleport mazes I had to brute-force, but I might have been missing a hint somewhere. I did make it through with only a little trouble, but alas — I stepped in a bad warp somewhere and got sent to the upper left corner of the starting screen, which is surrounded by walls. So Klyde’s new life is being trapped eternally in a nowhere space. FINAL SCORE: 19/20 apples ## And more That was only a third of the games, and I don’t think even half of the ones I’ve played. I’ll have to do a second post covering the rest of them? Maybe a third? Or maybe this is a ludicrous format for commenting on several dozen games and I should try to narrow it down to the ones that resonated the most for Strawberry Jam 2? Maybe?? # Weekly roundup: Potpourri 2 Post Syndicated from Eevee original https://eev.ee/dev/2018/01/23/weekly-roundup-potpourri-2/ • blog: I wrote a birthday post, as is tradition. I finally finished writing Game Night 2, a full month after we actually played those games. • art: I put together an art improvement chart for last year, after skipping doing it in July, tut tut. Kind of a weird rollercoaster! I worked a teeny bit on two one-off comics I guess but they aren’t reeeally getting anywhere fast. Comics are hard. I made a banner for Strawberry Jam 2 which I think came out fantastically! • games: I launched Strawberry Jam 2, a month-long February game jam about making horny games. I will probably be making a horny game for it. • idchoppers: I took another crack at dilation. Some meager progress, maybe. I think I’m now porting bad academic C++ to Rust to get the algorithm I want, and I can’t help but wonder if I could just make up something of my own faster than this. • fox flux: I did a bunch of brainstorming and consolidated a bunch of notes from like four different places, which feels like work but also feels like it doesn’t actually move the project forward. • anise!!: Ah, yes, this fell a bit by the wayside. Some map work, some attempts at a 3D effect for a particular thing without much luck (though I found a workaround in the last couple days). • computers: I relieved myself of some 200 browser tabs, which feels fantastic, though I’ve since opened like 80 more. Alas. I also tried to put together a firejail profile for running mystery games from the internet, and I got like 90% of the way there, but it turns out there’s basically no way to stop an X application from reading all keyboard input. (Yes, I know about that, and I tried it. Yes, that too.) I’ve got a small pile of little projects that are vaguely urgent, so as much as I’d love to bash my head against idchoppers for a solid week, I’m gonna try to focus on getting a couple half-done things full-done. And maybe try to find time for art regularly so I don’t fall out of practice? Huff puff. # Wine 3.0 released Post Syndicated from corbet original https://lwn.net/Articles/744741/rss Version 3.0 of the Wine Windows emulation layer has been released. “This release represents a year of development effort and over 6,000 individual changes. ” Most of the improvements seem to be around Direct3D graphics, but it also now possible to package up Wine as an Android app; see the release notes for details. # Build a Binary Clock with engineerish Post Syndicated from Alex Bate original https://www.raspberrypi.org/blog/engineerish-binary-clock/ Standard clocks with easily recognisable numbers are so last season. Who wants to save valuable seconds simply telling the time, when a series of LEDs and numerical notation can turn every time query into an adventure in mathematics? #### Build a Binary Clock with Raspberry Pi – And how to tell the time In this video I’ll be showing how I built a binary clock using a Raspberry Pi, NeoPixels and a few lines of Python. I also take a stab at explaining how the binary number system works so that we can decipher what said clock is trying to tell us. ## How to read binary I’ll be honest: I have to think pretty hard to read binary. It stretches my brain quite vigorously. But I am a fan of flashy lights and pretty builds, so YouTube and Instagram rising star Mattias Jähnke, aka engineerish, had my full attention from the off. “If you have a problem with your friends being able to tell the time way too easily while in your house, this is your answer.” Mattias offers a beginners’ guide in to binary in his video and then explains how his clock displays values in binary, before moving on to the actual clock build process. So make some tea, pull up a chair, and jump right in. ## Binary clock To build the clock, Mattias used a Raspberry Pi and NeoPixel strips, fitted snugly within a simple 3D-printed case. With a few lines of Python, he coded his clock to display the current time using the binary system, with columns for seconds, minutes, and hours. #### The real kicker with a binary clock is that by the time you’ve deciphered what time it is – you’re probably already late. 418 Likes, 14 Comments – Mattias (@engineerish) on Instagram: “The real kicker with a binary clock is that by the time you’ve deciphered what time it is – you’re…” The Python code isn’t currently available on Mattias’s GitHub account, but if you’re keen to see how he did it, and you ask politely, and he’s not too busy, you never know. ## Make your own In the meantime, while we batter our eyelashes in the general direction of Stockholm and hope for a response, I challenge any one of you to code a binary display project for the Raspberry Pi. It doesn’t have to be a clock. And it doesn’t have to use NeoPixels. Maybe it could use an LED matrix such as the SenseHat, or a series of independently controlled LEDs on a breadboard. Maybe there’s something to be done with servo motors that flip discs with different-coloured sides to display a binary number. Whatever you decide to build, the standard reward applies: ten imaginary house points (of absolutely no practical use, but immense emotional value) and a great sense of achievement to all who give it a go. The post Build a Binary Clock with engineerish appeared first on Raspberry Pi. # Eevee gained 2791 experience points Post Syndicated from Eevee original https://eev.ee/blog/2018/01/15/eevee-gained-2791-experience-points/ Eevee grew to level 31! A year strongly defined by mixed success! Also, a lot of video games. I ran three game jams, resulting in a total of 157 games existing that may not have otherwise, which is totally mindblowing?! For GAMES MADE QUICK???, glip and I made NEON PHASE, a short little exploratory platformer. Honestly, I should give myself more credit for this and the rest of the LÖVE games I’ve based on the same codebase — I wove a physics engine (and everything else!) from scratch and it has held up remarkably well for a variety of different uses. I successfully finished an HD version of Isaac’s Descent using my LÖVE engine, though it doesn’t have anything new over the original and I’ve only released it as a tech demo on Patreon. For Strawberry Jam (NSFW!) we made fox flux (slightly NSFW!), which felt like a huge milestone: the first game where I made all the art! I mean, not counting Isaac’s Descent, which was for a very limited platform. It’s a pretty arbitrary milestone, yes, but it feels significant. I’ve been working on expanding the game into a longer and slightly less buggy experience, but the art is taking the longest by far. I must’ve spent weeks on player sprites alone. We then set about working on Bolthaven, a sequel of sorts to NEON PHASE, and got decently far, and then abandond it. Oops. We then started a cute little PICO-8 game, and forgot about it. Oops. I was recruited to help with Chaos Composer, a more ambitious game glip started with someone else in Unity. I had to get used to Unity, and we squabbled a bit, but the game is finally about at the point where it’s “playable” and “maps” can be designed? It’s slightly on hold at the moment while we all finish up some other stuff, though. We made a birthday game for two of our friends whose birthdays were very close together! Only they got to see it. For Ludum Dare 38, we made Lunar Depot 38, a little “wave shooter” or whatever you call those? The AI is pretty rough, seeing as this was the first time I’d really made enemies and I had 72 hours to figure out how to do it, but I still think it’s pretty fun to play and I love the circular world. I made Roguelike Simulator as an experiment with making something small and quick with a simple tool, and I had a lot of fun! I definitely want to do more stuff like this in the future. And now we’re working on a game about Star Anise, my cat’s self-insert, which is looking to have more polish and depth than anything we’ve done so far! We’ve definitely come a long way in a year. Somewhere along the line, I put out a call for a “potluck” project, where everyone would give me sprites of a given size without knowing what anyone else had contributed, and I would then make a game using only those sprites. Unfortunately, that stalled a few times: I tried using the Phaser JS library, but we didn’t get along; I tried LÖVE, but didn’t know where to go with the game; and then I decided to use this as an experiment with procedural generation, and didn’t get around to it. I still feel bad that everyone did work for me and I didn’t follow through, but I don’t know whether this will ever become a game. veekun, alas, consumed months of my life. I finally got Sun and Moon loaded, but it took weeks of work since I was basically reinventing all the tooling we’d ever had from scratch, without even having most of that tooling available as a reference. It was worth it in the end, at least: Ultra Sun and Ultra Moon only took a few days to get loaded. But veekun itself is still missing some obvious Sun/Moon features, and the whole site needs an overhaul, and I just don’t know if I want to dedicate that much time to it when I have so much other stuff going on that’s much more interesting to me right now. I finally turned my blog into more of a website, giving it a neat front page that lists a bunch of stuff I’ve done. I made a release category at last, though I’m still not quite in the habit of using it. I wrote some blog posts, of course! I think the most interesting were JavaScript got better while I wasn’t looking and Object models. I was also asked to write a couple pieces for money for a column that then promptly shut down. On a whim, I made a set of Eevee mugshots for Doom, which I think is a decent indication of my (pixel) art progress over the year? I started idchoppers, a Doom parsing and manipulation library written in Rust, though it didn’t get very far and I’ve spent most of the time fighting with Rust because it won’t let me implement all my extremely bad ideas. It can do a couple things, at least, like flip maps very quickly and render maps to SVG. I did toy around with music a little, but not a lot. I wrote two short twines for Flora. They’re okay. I’m working on another; I think it’ll be better. I didn’t do a lot of art overall, at least compared to the two previous years; most of my art effort over the year has gone into fox flux, which requires me to learn a whole lot of things. I did dip my toes into 3D modelling, most notably producing my current Twitter banner as well as this cool Star Anise animation. I wouldn’t mind doing more of that; maybe I’ll even try to make a low-poly pixel-textured 3D game sometime. I restarted my book with a much better concept, though so far I’ve only written about half a chapter. Argh. I see that the vast majority of the work was done within the span of a single week, which is bad since that means I only worked on it for a week, but good since that means I can actually do a pretty good amount of work in only a week. I also did a lot of squabbling with tooling, which is hopefully mostly out of the way now. My computer broke? That was an exciting week. A lot of stuff, but the year as a whole still feels hit or miss. All the time I spent on veekun feels like a black void in the middle of the year, which seems like a good sign that I maybe don’t want to pour even more weeks into it in the near future. Mostly, I want to do: more games, more art, more writing, more music. I want to try out some tiny game making tools and make some tiny games with them — partly to get exposure to different things, partly to get more little ideas out into the world regularly, and partly to get more practice at letting myself have ideas. I have a couple tools in mind and I guess I’ll aim at a microgame every two months or so? I’d also like to finish the expanded fox flux by the end of the year, of course, though at the moment I can’t even gauge how long it might take. I seriously lapsed on drawing last year, largely because fox flux pixel art took me so much time. So I want to draw more, and I want to get much faster at pixel art. It would probably help if I had a more concrete goal for drawing, so I might try to draw some short comics and write a little visual novel or something, which would also force me to aim for consistency. I want to work on my book more, of course, but I also want to try my hand at a bit more fiction. I’ve had a blast writing dialogue for our games! I just shy away from longer-form writing for some reason — which seems ridiculous when a large part of my audience found me through my blog. I do think I’ve had some sort of breakthrough in the last month or two; I suddenly feel a good bit more confident about writing in general and figuring out what I want to say? One recent post I know I wrote in a single afternoon, which virtually never happens because I keep rewriting and rearranging stuff. Again, a visual novel would be a good excuse to practice writing fiction without getting too bogged down in details. And, ah, music. I shy heavily away from music, since I have no idea what I’m doing, and also I seem to spend a lot of time fighting with tools. (Surprise.) I tried out SunVox for the first time just a few days ago and have been enjoying it quite a bit for making sound effects, so I might try it for music as well. And once again, visual novel background music is a pretty low-pressure thing to compose for. Hell, visual novels are small games, too, so that checks all the boxes. I guess I’ll go make a visual novel. Here’s to twenty gayteen! # AWS IoT, Greengrass, and Machine Learning for Connected Vehicles at CES Post Syndicated from Jeff Barr original https://aws.amazon.com/blogs/aws/aws-iot-greengrass-and-machine-learning-for-connected-vehicles-at-ces/ Last week I attended a talk given by Bryan Mistele, president of Seattle-based INRIX. Bryan’s talk provided a glimpse into the future of transportation, centering around four principle attributes, often abbreviated as ACES: Autonomous – Cars and trucks are gaining the ability to scan and to make sense of their environments and to navigate without human input. Connected – Vehicles of all types have the ability to take advantage of bidirectional connections (either full-time or intermittent) to other cars and to cloud-based resources. They can upload road and performance data, communicate with each other to run in packs, and take advantage of traffic and weather data. Electric – Continued development of battery and motor technology, will make electrics vehicles more convenient, cost-effective, and environmentally friendly. Shared – Ride-sharing services will change usage from an ownership model to an as-a-service model (sound familiar?). Individually and in combination, these emerging attributes mean that the cars and trucks we will see and use in the decade to come will be markedly different than those of the past. On the Road with AWS AWS customers are already using our AWS IoT, edge computing, Amazon Machine Learning, and Alexa products to bring this future to life – vehicle manufacturers, their tier 1 suppliers, and AutoTech startups all use AWS for their ACES initiatives. AWS Greengrass is playing an important role here, attracting design wins and helping our customers to add processing power and machine learning inferencing at the edge. AWS customer Aptiv (formerly Delphi) talked about their Automated Mobility on Demand (AMoD) smart vehicle architecture in a AWS re:Invent session. Aptiv’s AMoD platform will use Greengrass and microservices to drive the onboard user experience, along with edge processing, monitoring, and control. Here’s an overview: Another customer, Denso of Japan (one of the world’s largest suppliers of auto components and software) is using Greengrass and AWS IoT to support their vision of Mobility as a Service (MaaS). Here’s a video: AWS at CES The AWS team will be out in force at CES in Las Vegas and would love to talk to you. They’ll be running demos that show how AWS can help to bring innovation and personalization to connected and autonomous vehicles. Personalized In-Vehicle Experience – This demo shows how AWS AI and Machine Learning can be used to create a highly personalized and branded in-vehicle experience. It makes use of Amazon Lex, Polly, and Amazon Rekognition, but the design is flexible and can be used with other services as well. The demo encompasses driver registration, login and startup (including facial recognition), voice assistance for contextual guidance, personalized e-commerce, and vehicle control. Here’s the architecture for the voice assistance: Connected Vehicle Solution – This demo shows how a connected vehicle can combine local and cloud intelligence, using edge computing and machine learning at the edge. It handles intermittent connections and uses AWS DeepLens to train a model that responds to distracted drivers. Here’s the overall architecture, as described in our Connected Vehicle Solution: Digital Content Delivery – This demo will show how a customer uses a web-based 3D configurator to build and personalize their vehicle. It will also show high resolution (4K) 3D image and an optional immersive AR/VR experience, both designed for use within a dealership. Autonomous Driving – This demo will showcase the AWS services that can be used to build autonomous vehicles. There’s a 1/16th scale model vehicle powered and driven by Greengrass and an overview of a new AWS Autonomous Toolkit. As part of the demo, attendees drive the car, training a model via Amazon SageMaker for subsequent on-board inferencing, powered by Greengrass ML Inferencing. To speak to one of my colleagues or to set up a time to see the demos, check out the Visit AWS at CES 2018 page. Some Resources If you are interested in this topic and want to learn more, the AWS for Automotive page is a great starting point, with discussions on connected vehicles & mobility, autonomous vehicle development, and digital customer engagement. When you are ready to start building a connected vehicle, the AWS Connected Vehicle Solution contains a reference architecture that combines local computing, sophisticated event rules, and cloud-based data processing and storage. You can use this solution to accelerate your own connected vehicle projects. Jeff; # Turn your smartphone into a universal remote Post Syndicated from Alex Bate original https://www.raspberrypi.org/blog/zero-universal-remote/ Honolulu-based software developer bbtinkerer was tired of never being able to find the TV remote. So he made his own using a Raspberry Pi Zero, and connected it to a web app accessible on his smartphone. ## Finding a remote alternative “I needed one because the remote in my house tends to go missing a lot,” explains Bernard aka bbtinkerer on the Instructables page for his Raspberry Pi Zero Universal Remote.”If I want the controller, I have to hunt down three people and hope one of them remembers that they took it.” For the build, Bernard used a Raspberry Pi Zero, an IR LED and corresponding receiver, Raspbian Lite, and a neat little 3D-printed housing. First, he soldered a circuit for the LED and resistors on a small piece of perf board. Then he assembled the hardware components. Finally, all he needed to do was to write the code to control his devices (including a tower fan), and to set up the app. Bernard employed the Linux Infrared Remote Control (LIRC) package to control the television with the Raspberry Pi Zero, accessing the Zero via SSH. He gives a complete rundown of the installation process on Instructables. Setting up a remote’s buttons with LIRC is a simple case of pressing them and naming their functions one by one. You’ll need the remote to set up the system, but after that, feel free to lock it in a drawer and use your smartphone instead. Finally, Bernard created the web interface using Node.js, and again, because he’s lovely, he published the code for anyone wanting to build their own. Thanks, Bernard! ## Life hacks If you’ve used a Raspberry Pi to build a time-saving life hack like Bernard’s, be sure to share it with us. Other favourites of ours include fridge cameras, phone app doorbell notifications, and Alan’s ocarina home automation system. I’m not sure if this last one can truly be considered a time-saving life hack. It’s still cool though! The post Turn your smartphone into a universal remote appeared first on Raspberry Pi. # Wanted: Sales Engineer Post Syndicated from Yev original https://www.backblaze.com/blog/wanted-sales-engineer/ At inception, Backblaze was a consumer company. Thousands upon thousands of individuals came to our website and gave us5/mo to keep their data safe. But, we didn’t sell business solutions. It took us years before we had a sales team. In the last couple of years, we’ve released products that businesses of all sizes love: Backblaze B2 Cloud Storage and Backblaze for Business Computer Backup. Those businesses want to integrate Backblaze deeply into their infrastructure, so it’s time to hire our first Sales Engineer!

Company Description:
Founded in 2007, Backblaze started with a mission to make backup software elegant and provide complete peace of mind. Over the course of almost a decade, we have become a pioneer in robust, scalable low cost cloud backup. Recently, we launched B2 – robust and reliable object storage at just \$0.005/gb/mo. Part of our differentiation is being able to offer the lowest price of any of the big players while still being profitable.

We’ve managed to nurture a team oriented culture with amazingly low turnover. We value our people and their families. Don’t forget to check out our “About Us” page to learn more about the people and some of our perks.

We have built a profitable, high growth business. While we love our investors, we have maintained control over the business. That means our corporate goals are simple – grow sustainably and profitably.

Some Backblaze Perks:

• Competitive healthcare plans
• Competitive compensation and 401k
• All employees receive Option grants
• Unlimited vacation days
• Strong coffee
• Fully stocked Micro kitchen
• Catered breakfast and lunches
• Awesome people who work on awesome projects
• Childcare bonus
• Normal work hours
• Get to bring your pets into the office
• San Mateo Office – located near Caltrain and Highways 101 & 280.

Backblaze B2 cloud storage is a building block for almost any computing service that requires storage. Customers need our help integrating B2 into iOS apps to Docker containers. Some customers integrate directly to the API using the programming language of their choice, others want to solve a specific problem using ready made software, already integrated with B2.

At the same time, our computer backup product is deepening it’s integration into enterprise IT systems. We are commonly asked for how to set Windows policies, integrate with Active Directory, and install the client via remote management tools.

We are looking for a sales engineer who can help our customers navigate the integration of Backblaze into their technical environments.

Are you 1/2” deep into many different technologies, and unafraid to dive deeper?

Can you confidently talk with customers about their technology, even if you have to look up all the acronyms right after the call?

Are you excited to setup complicated software in a lab and write knowledge base articles about your work?

Then Backblaze is the place for you!

In this role, you will be given the opportunity to learn about the technologies that drive innovation today; diverse technologies that customers are using day in and out. And more importantly, you’ll learn how to learn new technologies.

Just as an example, in the past 12 months, we’ve had the opportunity to learn and become experts in these diverse technologies:

• How to setup VM servers for lab environments, both on-prem and using cloud services.
• Create an automatically “resetting” demo environment for the sales team.
• Setup Microsoft Domain Controllers with Active Directory and AD Federation Services.
• Learn the basics of OAUTH and web single sign on (SSO).
• Archive video workflows from camera to media asset management systems.
• How to install and monitor online backup installations using RMM tools, like JAMF.
• Tape (LTO) systems. (Yes – people still use tape for storage!)

How can I know if I’ll succeed in this role?

You have:

• Confidence. Be able to ask customers questions about their environments and convey to them your technical acumen.
• Curiosity. Always want to learn about customers’ situations, how they got there and what problems they are trying to solve.
• Organization. You’ll work with customers, integration partners, and Backblaze team members on projects of various lengths. You can context switch and either have a great memory or keep copious notes. Your checklists have their own checklists.

You are versed in:

• The fundamentals of Windows, Linux and Mac OS X operating systems. You shouldn’t be afraid to use a command line.
• Building, installing, integrating and configuring applications on any operating system.
• Debugging failures – reading logs, monitoring usage, effective google searching to fix problems excites you.
• The basics of TCP/IP networking and the HTTP protocol.
• Novice development skills in any programming/scripting language. Have basic understanding of data structures and program flow.

• Bachelor’s degree in computer science or the equivalent.
• 2+ years of experience as a pre or post-sales engineer.
• The right extra credit:
There are literally hundreds of previous experiences you can have had that would make you perfect for this job. Some experiences that we know would be helpful for us are below, but make sure you tell us your stories!

• Experience using or programming against Amazon S3.
• Experience with large on-prem storage – NAS, SAN, Object. And backing up data on such storage with tools like Veeam, Veritas and others.
• Experience with photo or video media. Media archiving is a key market for Backblaze B2.
• Program arduinos to automatically feed your dog.
• Experience programming against web or REST APIs. (Point us towards your projects, if they are open source and available to link to.)
• Experience with sales tools like Salesforce.
• 3D print door stops.
• Experience with Windows Servers, Active Directory, Group policies and the like.
• What’s it like working with the Sales team?
The Backblaze sales team collaborates. We help each other out by sharing ideas, templates, and our customer’s experiences. When we talk about our accomplishments, there is no “I did this,” only “we”. We are truly a team.

We are honest to each other and our customers and communicate openly. We aim to have fun by embracing crazy ideas and creative solutions. We try to think not outside the box, but with no boxes at all. Customers are the driving force behind the success of the company and we care deeply about their success.

If this all sounds like you:

1. Send an email to [email protected] with the position in the subject line.

The post Wanted: Sales Engineer appeared first on Backblaze Blog | Cloud Storage & Cloud Backup.

# I am Beemo, a little living boy: Adventure Time prop build

Post Syndicated from Alex Bate original https://www.raspberrypi.org/blog/adventure-time-bmo/

Bob Herzberg, BMO builder and blogger at BYOBMO.com, fills us in on the whys and hows and even the Pen Wards of creating interactive Adventure Time BMO props with the Raspberry Pi.

#### A Conversation With BMO

A conversation with BMO showing off some voice recognition capabilities. There is no interaction for BMO’s responses other than voice commands. There is a small microphone inside BMO (right behind the blue dot) and the voice commands are processed by Google voice API over WiFi.

## Finding BMO

My first BMO began as a cosplay prop for my daughter. She and her friends are huge fans of Adventure Time and made their costumes for Princess Bubblegum, Marceline, and Finn. It was my job to come up with a BMO.

Bob as Banana Guard, daughter Laura as Princess Bubblegum, and son Steven as Finn

I wanted something electronic, and also interactive if possible. And it had to run on battery power. There was only one option that I found that would work: the Raspberry Pi.

## Building a living little boy

BMO’s basic internals consist of the Raspberry Pi, an 8” HDMI monitor, and a USB battery pack. The body is made from laser-cut MDF wood, which I sanded, sealed, and painted. I added 3D-printed arms and legs along with some vinyl lettering to complete the look. There is also a small wireless keyboard that works as a remote control.

To make the front panel button function, I created a custom PCB, mounted laser-cut acrylic buttons on it, and connected it to the Pi’s IO header.

Custom-made PCBs control BMO’s gaming buttons and USB input.

The USB jack is extended with another custom PCB, which gives BMO USB ports on the front panel. His battery life is an impressive 8 hours of continuous use.

## The main brain game frame

Most of BMO’s personality comes from custom animations that my daughter created and that were then turned into MP4 video files. The animations are triggered by the remote keyboard. Some versions of BMO have an internal microphone, and the Google Voice API is used to translate the user’s voice and map it to an appropriate response, so it’s possible to have a conversation with BMO.

The Raspberry Pi Camera Module was also put to use. Some BMOs have a servo that can pop up a camera, called GoMO, which takes pictures. Although some people mistake it for ghost detecting equipment, BMO just likes taking nice pictures.

## Who wants to play video games?

Playing games on BMO is as simple as loading one of the emulators supported by Raspbian.

I’m partial to the Atari 800 emulator, since I used to write games for that platform when I was just starting to learn programming. The front-panel USB ports are used for connecting gamepads, or his front-panel buttons and D-Pad can be used.

BMO has been a lot of fun to bring to conventions. He makes it to ComicCon San Diego each year and has been as far away as DragonCon in Atlanta, where he finally got to meet the voice of BMO, Niki Yang.

BMO’s back panel, autographed by Niki Yang

One day, I received an email from the producer of Adventure Time, Kelly Crews, with a very special request. Kelly was looking for a birthday present for the show’s creator, Pendleton Ward. It was either luck or coincidence that I just was finishing up the latest version of BMO. Niki Yang added some custom greetings just for Pen.

#### BMO Wishes Pendleton Ward a Happy Birthday!

Happy birthday to Pendleton Ward, the creator of, well, you know what. We were asked to build Pen his very own BMO and with help from Niki Yang and the Adventure Time crew here is the result.

We added a few more items inside, including a 3D-printed heart, a medal, and a certificate which come from the famous Be More episode that explains BMO’s origins.

BMO was quite a challenge to create. Fabricating the enclosure required several different techniques and materials. Fortunately, bringing him to life was quite simple once he had a Raspberry Pi inside!

## Find out more

Be sure to follow Bob’s adventures with BMO at the Build Your Own BMO blog. And if you’ve built your own prop from television or film using a Raspberry Pi, be sure to share it with us in the comments below or on our social media channels.

All images c/o Bob and Laura Herzberg

The post I am Beemo, a little living boy: Adventure Time prop build appeared first on Raspberry Pi.

# Physics cheats

Post Syndicated from Eevee original https://eev.ee/blog/2018/01/06/physics-cheats/

something about how we tweak physics to “work” better in games?

Ho ho! Work. Get it? Like in physics…?

## Hitboxes

Hitbox” is perhaps not the most accurate term, since the shape used for colliding with the environment and the shape used for detecting damage might be totally different. They’re usually the same in simple platformers, though, and that’s what most of my games have been.

The hitbox is the biggest physics fudge by far, and it exists because of a single massive approximation that (most) games make: you’re controlling a single entity in the abstract, not a physical body in great detail.

That is: when you walk with your real-world meat shell, you perform a complex dance of putting one foot in front of the other, a motion you spent years perfecting. When you walk in a video game, you press a single “walk” button. Your avatar may play an animation that moves its legs back and forth, but since you’re not actually controlling the legs independently (and since simulating them is way harder), the game just treats you like a simple shape. Fairly often, this is a box, or something very box-like.

Since the player has no direct control over the exact placement of their limbs, it would be slightly frustrating to have them collide with the world. This is especially true in cases like the above, where the tail and left ear protrude significantly out from the main body. If that Eevee wanted to stand against a real-world wall, she would simply tilt her ear or tail out of the way, so there’s no reason for the ear to block her from standing against a game wall. To compensate for this, the ear and tail are left out of the collision box entirely and will simply jut into a wall if necessary — a goofy affordance that’s so common it doesn’t even register as unusual. As a bonus (assuming this same box is used for combat), she won’t take damage from projectiles that merely graze past an ear.

(One extra consideration for sprite games in particular: the hitbox ought to be horizontally symmetric around the sprite’s pivot — i.e. the point where the entity is truly considered to be standing — so that the hitbox doesn’t abruptly move when the entity turns around!)

### Corners

Treating the player (and indeed most objects) as a box has one annoying side effect: boxes have corners. Corners can catch on other corners, even by a single pixel. Real-world bodies tend to be a bit rounder and squishier and this can tolerate grazing a corner; even real-world boxes will simply rotate a bit.

Ah, but in our faux physics world, we generally don’t want conscious actors (such as the player) to rotate, even with a realistic physics simulator! Real-world bodies are made of parts that will generally try to keep you upright, after all; you don’t tilt back and forth much.

One way to handle corners is to simply remove them from conscious actors. A hitbox doesn’t have to be a literal box, after all. A popular alternative — especially in Unity where it’s a standard asset — is the pill-shaped capsule, which has semicircles/hemispheres on the top and bottom and a cylindrical body in 3D. No corners, no problem.

Of course, that introduces a new problem: now the player can’t balance precariously on edges without their rounded bottom sliding them off. Alas.

If you’re stuck with corners, then, you may want to use a corner bump, a term I just made up. If the player would collide with a corner, but the collision is only by a few pixels, just nudge them to the side a bit and carry on.

When the corner is horizontal, this creates stairs! This is, more or less kinda, how steps work in Doom: when the player tries to cross from one sector into another, if the height difference is 24 units or less, the game simply bumps them upwards to the height of the new floor and lets them continue on.

Implementing this in a game without Doom’s notion of sectors is a little trickier. In fact, I still haven’t done it. Collision detection based on rejection gets it for free, kinda, but it’s not very deterministic and it breaks other things. But that’s a whole other post.

## Gravity

Gravity is pretty easy. Everything accelerates downwards all the time. What’s interesting are the exceptions.

### Jumping

Jumping is a giant hack.

Think about how actual jumping works: you tense your legs, which generally involves bending your knees first, and then spring upwards. In a platformer, you can just leap whenever you feel like it, which is nonsense. Also you go like twenty feet into the air?

Worse, most platformers allow variable-height jumping, where your jump is lower if you let go of the jump button while you’re in the air. Normally, one would expect to have to decide how much force to put into the jump beforehand.

But of course this is about convenience of controls: when jumping is your primary action, you want to be able to do it immediately, without any windup for how high you want to jump.

(And then there’s double jumping? Come on.)

Air control is a similar phenomenon: usually you’d jump in a particular direction by controlling how you push off the ground with your feet, but in a video game, you don’t have feet! You only have the box. The compromise is to let you control your horizontal movement to a limit degree in midair, even though that doesn’t make any sense. (It’s way more fun, though, and overall gives you more movement options, which are good to have in an interactive medium.)

Air control also exposes an obvious place that game physics collide with the realistic model of serious physics engines. I’ve mentioned this before, but: if you use Real Physics™ and air control yourself into a wall, you might find that you’ll simply stick to the wall until you let go of the movement buttons. Why? Remember, player movement acts as though an external force were pushing you around (and from the perspective of a Real™ physics engine, this is exactly how you’d implement it) — so air-controlling into a wall is equivalent to pushing a book against a wall with your hand, and the friction with the wall holds you in place. Oops.

### Ground sticking

Another place game physics conflict with physics engines is with running to the top of a slope. On a real hill, of course, you land on top of the slope and are probably glad of it; slopes are hard to climb!

In a video game, you go flying. Because you’re a box. With momentum. So you hit the peak and keep going in the same direction. Which is diagonally upwards.

### Projectiles

To make them more predictable, projectiles generally aren’t subject to gravity, at least as far as I’ve seen. The real world does not have such an exemption. The real world imposes gravity even on sniper rifles, which in a video game are often implemented as an instant trace unaffected by anything in the world because the bullet never actually exists in the world.

## Resistance

Ah. Welcome to hell.

### Water

Water is an interesting case, and offhand I don’t know the gritty details of how games implement it. In the real world, water applies a resistant drag force to movement — and that force is proportional to the square of velocity, which I’d completely forgotten until right now. I am almost positive that no game handles that correctly. But then, in real-world water, you can push against the water itself for movement, and games don’t simulate that either. What’s the rough equivalent?

The Sonic Physics Guide suggests that Sonic handles it by basically halving everything: acceleration, max speed, friction, etc. When Sonic enters water, his speed is cut; when Sonic exits water, his speed is increased.

That last bit feels validating — I could swear Metroid Prime did the same thing, and built my own solution around it, but couldn’t remember for sure. It makes no sense, of course, for a jump to become faster just because you happened to break the surface of the water, but it feels fantastic.

The thing I did was similar, except that I didn’t want to add a multiplier in a dozen places when you happen to be underwater (and remember which ones need it to be squared, etc.). So instead, I calculate everything completely as normal, so velocity is exactly the same as it would be on dry land — but the distance you would move gets halved. The effect seems to be pretty similar to most platformers with water, at least as far as I can tell. It hasn’t shown up in a published game and I only added this fairly recently, so I might be overlooking some reason this is a bad idea.

(One reason that comes to mind is that velocity is now a little white lie while underwater, so anything relying on velocity for interesting effects might be thrown off. Or maybe that’s correct, because velocity thresholds should be halved underwater too? Hm!)

Notably, air is also a fluid, so it should behave the same way (just with different constants). I definitely don’t think any games apply air drag that’s proportional to the square of velocity.

### Friction

Friction is, in my experience, a little handwaved. Probably because real-world friction is so darn complicated.

Consider that in the real world, we want very high friction on the surfaces we walk on — shoes and tires are explicitly designed to increase it, even. We move by bracing a back foot against the ground and using that to push ourselves forward, so we want the ground to resist our push as much as possible.

In a game world, we are a box. We move by being pushed by some invisible outside force, so if the friction between ourselves and the ground is too high, we won’t be able to move at all! That’s complete nonsense physically, but it turns out to be handy in some cases — for example, highish friction can simulate walking through deep mud, which should be difficult due to fluid drag and low friction.

But the best-known example of the fakeness of game friction is video game ice. Walking on real-world ice is difficult because the low friction means low grip; your feet are likely to slip out from under you, and you’ll simply fall down and have trouble moving at all. In a video game, you can’t fall down, so you have the opposite experience: you spend most of your time sliding around uncontrollably. Yet ice is so common in video games (and perhaps so uncommon in places I’ve lived) that I, at least, had never really thought about this disparity until an hour or so ago.

### Game friction vs real-world friction

Real-world friction is a force. It’s the normal force (which is the force exerted by the object on the surface) times some constant that depends on how the two materials interact.

Force is mass times acceleration, and platformers often ignore mass, so friction ought to be an acceleration — applied against the object’s movement, but never enough to push it backwards.

I haven’t made any games where variable friction plays a significant role, but my gut instinct is that low friction should mean the player accelerates more slowly but has a higher max speed, and high friction should mean the opposite. I see from my own source code that I didn’t even do what I just said, so let’s defer to some better-made and well-documented games: Sonic and Doom.

In Sonic, friction is a fixed value subtracted from the player’s velocity (regardless of direction) each tic. Sonic has a fixed framerate, so the units are really pixels per tic squared (i.e. acceleration), multiplied by an implicit 1 tic per tic. So far, so good.

But Sonic’s friction only applies if the player isn’t pressing or . Hang on, that isn’t friction at all; that’s just deceleration! That’s equivalent to jogging to a stop. If friction were lower, Sonic would take longer to stop, but otherwise this is only tangentially related to friction.

(In fairness, this approach would decently emulate friction for non-conscious sliding objects, which are never going to be pressing movement buttons. Also, we don’t have the Sonic source code, and the name “friction” is a fan invention; the Sonic Physics Guide already uses “deceleration” to describe the player’s acceleration when turning around.)

Okay, let’s try Doom. In Doom, the default friction is 90.625%.

Hang on, what?

Yes, in Doom, friction is a multiplier applied every tic. Doom runs at 35 tics per second, so this is a multiplier of 0.032 per second. Yikes!

This isn’t anything remotely like real friction, but it’s much easier to implement. With friction as acceleration, the game has to know both the direction of movement (so it can apply friction in the opposite direction) and the magnitude (so it doesn’t overshoot and launch the object in the other direction). That means taking a semi-costly square root and also writing extra code to cap the amount of friction. With a multiplier, neither is necessary; just multiply the whole velocity vector and you’re done.

There are some downsides. One is that objects will never actually stop, since multiplying by 3% repeatedly will never produce a result of zero — though eventually the speed will become small enough to either slip below a “minimum speed” threshold or simply no longer fit in a float representation. Another is that the units are fairly meaningless: with Doom’s default friction of 90.625%, about how long does it take for the player to stop? I have no idea, partly because “stop” is ambiguous here! If friction were an acceleration, I could divide it into the player’s max speed to get a time.

All that aside, what are the actual effects of changing Doom’s friction? What an excellent question that’s surprisingly tricky to answer. (Note that friction can’t be changed in original Doom, only in the Boom port and its derivatives.) Here’s what I’ve pieced together.

Doom’s “friction” is really two values. “Friction” itself is a multiplier applied to moving objects on every tic, but there’s also a move factor which defaults to $$\frac{1}{32} = 0.03125$$ and is derived from friction for custom values.

Every tic, the player’s velocity is multiplied by friction, and then increased by their speed times the move factor.

$$v(n) = v(n – 1) \times friction + speed \times move factor$$

Eventually, the reduction from friction will balance out the speed boost. That happens when $$v(n) = v(n – 1)$$, so we can rearrange it to find the player’s effective max speed:

$$v = v \times friction + speed \times move factor \\ v – v \times friction = speed \times move factor \\ v = speed \times \frac{move factor}{1 – friction}$$

For vanilla Doom’s move factor of 0.03125 and friction of 0.90625, that becomes:

$$v = speed \times \frac{\frac{1}{32}}{1 – \frac{29}{32}} = speed \times \frac{\frac{1}{32}}{\frac{3}{32}} = \frac{1}{3} \times speed$$

Curiously, “speed” is three times the maximum speed an actor can actually move. Doomguy’s run speed is 50, so in practice he moves a third of that, or 16⅔ units per tic. (Of course, this isn’t counting SR40, a bug that lets Doomguy run ~40% faster than intended diagonally.)

So now, what if you change friction? Even more curiously, the move factor is calculated completely differently depending on whether friction is higher or lower than the default Doom amount:

$$move factor = \begin{cases} \frac{133 – 128 \times friction}{544} &≈ 0.244 – 0.235 \times friction & \text{ if } friction \ge \frac{29}{32} \\ \frac{81920 \times friction – 70145}{1048576} &≈ 0.078 \times friction – 0.067 & \text{ otherwise } \end{cases}$$

That’s pretty weird? Complicating things further is that low friction (which means muddy terrain, remember) has an extra multiplier on its move factor, depending on how fast you’re already going — the idea is apparently that you have a hard time getting going, but it gets easier as you find your footing. The extra multiplier maxes out at 8, which makes the two halves of that function meet at the vanilla Doom value.

That very top point corresponds to the move factor from the original game. So no matter what you do to friction, the move factor becomes lower. At 0.85 and change, you can no longer move at all; below that, you move backwards.

From the formula above, it’s easy to see what changes to friction and move factor will do to Doomguy’s stable velocity. Move factor is in the numerator, so increasing it will increase stable velocity — but it can’t increase, so stable velocity can only ever decrease. Friction is in the denominator, but it’s subtracted from 1, so increasing friction will make the denominator a smaller value less than 1, i.e. increase stable velocity. Combined, we get this relationship between friction and stable velocity.

As friction approaches 1, stable velocity grows without bound. This makes sense, given the definition of $$v(n)$$ — if friction is 1, the velocity from the previous tic isn’t reduced at all, so we just keep accelerating freely.

All of this is why I’m wary of using multipliers.

Anyway, this leaves me with one last question about the effects of Doom’s friction: how long does it take to reach stable velocity? Barring precision errors, we’ll never truly reach stable velocity, but let’s say within 5%. First we need a closed formula for the velocity after some number of tics. This is a simple recurrence relation, and you can write a few terms out yourself if you want to be sure this is right.

$$v(n) = v_0 \times friction^n + speed \times move factor \times \frac{friction^n – 1}{friction – 1}$$

Our initial velocity is zero, so the first term disappears. Set this equal to the stable formula and solve for n:

$$speed \times move factor \times \frac{friction^n – 1}{friction – 1} = (1 – 5\%) \times speed \times \frac{move factor}{1 – friction} \\ friction^n – 1 = -(1 – 5\%) \\ n = \frac{\ln 5\%}{\ln friction}$$

Speed” and move factor disappear entirely, which makes sense, and this is purely a function of friction (and how close we want to get). For vanilla Doom, that comes out to 30.4, which is a little less than a second. For other values of friction:

As friction increases (which in Doom terms means the surface is more slippery), it takes longer and longer to reach stable speed, which is in turn greater and greater. For lesser friction (i.e. mud), stable speed is lower, but reached fairly quickly. (Of course, the extra “getting going” multiplier while in mud adds some extra time here, but including that in the graph is a bit more complicated.)

I think this matches with my instincts above. How fascinating!

What’s that? This is way too much math and you hate it? Then don’t use multipliers in game physics.

## Uh

That was a hell of a diversion!

I guess the goofiest stuff in basic game physics is really just about mapping player controls to in-game actions like jumping and deceleration; the rest consists of hacks to compensate for representing everything as a box.

# Some notes on Meltdown/Spectre

Post Syndicated from Robert Graham original http://blog.erratasec.com/2018/01/some-notes-on-meltdownspectre.html

I thought I’d write up some notes.

You don’t have to worry if you patch. If you download the latest update from Microsoft, Apple, or Linux, then the problem is fixed for you and you don’t have to worry. If you aren’t up to date, then there’s a lot of other nasties out there you should probably also be worrying about. I mention this because while this bug is big in the news, it’s probably not news the average consumer needs to concern themselves with.

This will force a redesign of CPUs and operating systems. While not a big news item for consumers, it’s huge in the geek world. We’ll need to redesign operating systems and how CPUs are made.

Don’t worry about the performance hit. Some, especially avid gamers, are concerned about the claims of “30%” performance reduction when applying the patch. That’s only in some rare cases, so you shouldn’t worry too much about it. As far as I can tell, 3D games aren’t likely to see less than 1% performance degradation. If you imagine your game is suddenly slower after the patch, then something else broke it.

This wasn’t foreseeable. A common cliche is that such bugs happen because people don’t take security seriously, or that they are taking “shortcuts”. That’s not the case here. Speculative execution and timing issues with caches are inherent issues with CPU hardware. “Fixing” this would make CPUs run ten times slower. Thus, while we can tweek hardware going forward, the larger change will be in software.

There’s no good way to disclose this. The cybersecurity industry has a process for coordinating the release of such bugs, which appears to have broken down. In truth, it didn’t. Once Linus announced a security patch that would degrade performance of the Linux kernel, we knew the coming bug was going to be Big. Looking at the Linux patch, tracking backwards to the bug was only a matter of time. Hence, the release of this information was a bit sooner than some wanted. This is to be expected, and is nothing to be upset about.

It helps to have a name. Many are offended by the crassness of naming vulnerabilities and giving them logos. On the other hand, we are going to be talking about these bugs for the next decade. Having a recognizable name, rather than a hard-to-remember number, is useful.

Should I stop buying Intel? Intel has the worst of the bugs here. On the other hand, ARM and AMD alternatives have their own problems. Many want to deploy ARM servers in their data centers, but these are likely to expose bugs you don’t see on x86 servers. The software fix, “page table isolation”, seems to work, so there might not be anything to worry about. On the other hand, holding up purchases because of “fear” of this bug is a good way to squeeze price reductions out of your vendor. Conversely, later generation CPUs, “Haswell” and even “Skylake” seem to have the least performance degradation, so it might be time to upgrade older servers to newer processors.

Intel misleads. Intel has a press release that implies they are not impacted any worse than others. This is wrong: the “Meltdown” issue appears to apply only to Intel CPUs. I don’t like such marketing crap, so I mention it.

Statements from companies:

# Random with care

Post Syndicated from Eevee original https://eev.ee/blog/2018/01/02/random-with-care/

Hi! Here are a few loose thoughts about picking random numbers.

This is all aimed at frivolous pursuits like video games. Hell, even video games where money is at stake should be deferring to someone who knows way more than I do. Otherwise you might find out that your deck shuffles in your poker game are woefully inadequate and some smartass is cheating you out of millions. (If your random number generator has fewer than 226 bits of state, it can’t even generate every possible shuffling of a deck of cards!)

## Use the right distribution

Most languages have a random number primitive that spits out a number uniformly in the range [0, 1), and you can go pretty far with just that. But beware a few traps!

### Random pitches

Say you want to pitch up a sound by a random amount, perhaps up to an octave. Your audio API probably has a way to do this that takes a pitch multiplier, where I say “probably” because that’s how the only audio API I’ve used works.

Easy peasy. If 1 is unchanged and 2 is pitched up by an octave, then all you need is rand() + 1. Right?

No! Pitch is exponential — within the same octave, the “gap” between C and C♯ is about half as big as the gap between B and the following C. If you pick a pitch multiplier uniformly, you’ll have a noticeable bias towards the higher pitches.

One octave corresponds to a doubling of pitch, so if you want to pick a random note, you want 2 ** rand().

### Random directions

For two dimensions, you can just pick a random angle with rand() * TAU.

If you want a vector rather than an angle, or if you want a random direction in three dimensions, it’s a little trickier. You might be tempted to just pick a random point where each component is rand() * 2 - 1 (ranging from −1 to 1), but that’s not quite right. A direction is a point on the surface (or, equivalently, within the volume) of a sphere, and picking each component independently produces a point within the volume of a cube; the result will be a bias towards the corners of the cube, where there’s much more extra volume beyond the sphere.

No? Well, just trust me. I don’t know how to make a diagram for this.

Anyway, you could use the Pythagorean theorem a few times and make a huge mess of things, or it turns out there’s a really easy way that even works for two or four or any number of dimensions. You pick each coordinate from a Gaussian (normal) distribution, then normalize the resulting vector. In other words, using Python’s random module:

 1 2 3 4 5 6 def random_direction(): x = random.gauss(0, 1) y = random.gauss(0, 1) z = random.gauss(0, 1) r = math.sqrt(x*x + y*y + z*z) return x/r, y/r, z/r 

Why does this work? I have no idea!

Note that it is possible to get zero (or close to it) for every component, in which case the result is nonsense. You can re-roll all the components if necessary; just check that the magnitude (or its square) is less than some epsilon, which is equivalent to throwing away a tiny sphere at the center and shouldn’t affect the distribution.

### Beware Gauss

Since I brought it up: the Gaussian distribution is a pretty nice one for choosing things in some range, where the middle is the common case and should appear more frequently.

That said, I never use it, because it has one annoying drawback: the Gaussian distribution has no minimum or maximum value, so you can’t really scale it down to the range you want. In theory, you might get any value out of it, with no limit on scale.

In practice, it’s astronomically rare to actually get such a value out. I did a hundred million trials just to see what would happen, and the largest value produced was 5.8.

But, still, I’d rather not knowingly put extremely rare corner cases in my code if I can at all avoid it. I could clamp the ends, but that would cause unnatural bunching at the endpoints. I could reroll if I got a value outside some desired range, but I prefer to avoid rerolling when I can, too; after all, it’s still (astronomically) possible to have to reroll for an indefinite amount of time. (Okay, it’s really not, since you’ll eventually hit the period of your PRNG. Still, though.) I don’t bend over backwards here — I did just say to reroll when picking a random direction, after all — but when there’s a nicer alternative I’ll gladly use it.

And lo, there is a nicer alternative! Enter the beta distribution. It always spits out a number in [0, 1], so you can easily swap it in for the standard normal function, but it takes two “shape” parameters α and β that alter its behavior fairly dramatically.

With α = β = 1, the beta distribution is uniform, i.e. no different from rand(). As α increases, the distribution skews towards the right, and as β increases, the distribution skews towards the left. If α = β, the whole thing is symmetric with a hump in the middle. The higher either one gets, the more extreme the hump (meaning that value is far more common than any other). With a little fiddling, you can get a number of interesting curves.

Screenshots don’t really do it justice, so here’s a little Wolfram widget that lets you play with α and β live:

Note that if α = 1, then 1 is a possible value; if β = 1, then 0 is a possible value. You probably want them both greater than 1, which clamps the endpoints to zero.

Also, it’s possible to have either α or β or both be less than 1, but this creates very different behavior: the corresponding endpoints become poles.

Anyway, something like α = β = 3 is probably close enough to normal for most purposes but already clamped for you. And you could easily replicate something like, say, NetHack’s incredibly bizarre rnz function.

### Random frequency

Say you want some event to have an 80% chance to happen every second. You (who am I kidding, I) might be tempted to do something like this:

 1 2 if random() < 0.8 * dt: do_thing() 

In an ideal world, dt is always the same and is equal to 1 / f, where f is the framerate. Replace that 80% with a variable, say P, and every tic you have a P / f chance to do the… whatever it is.

Each second, f tics pass, so you’ll make this check f times. The chance that any check succeeds is the inverse of the chance that every check fails, which is $$1 – \left(1 – \frac{P}{f}\right)^f$$.

For P of 80% and a framerate of 60, that’s a total probability of 55.3%. Wait, what?

Consider what happens if the framerate is 2. On the first tic, you roll 0.4 twice — but probabilities are combined by multiplying, and splitting work up by dt only works for additive quantities. You lose some accuracy along the way. If you’re dealing with something that multiplies, you need an exponent somewhere.

But in this case, maybe you don’t want that at all. Each separate roll you make might independently succeed, so it’s possible (but very unlikely) that the event will happen 60 times within a single second! Or 200 times, if that’s someone’s framerate.

If you explicitly want something to have a chance to happen on a specific interval, you have to check on that interval. If you don’t have a gizmo handy to run code on an interval, it’s easy to do yourself with a time buffer:

 1 2 3 4 5 6 timer += dt # here, 1 is the "every 1 seconds" while timer > 1: timer -= 1 if random() < 0.8: do_thing() 

Using while means rolls still happen even if you somehow skipped over an entire second.

(For the curious, and the nerds who already noticed: the expression $$1 – \left(1 – \frac{P}{f}\right)^f$$ converges to a specific value! As the framerate increases, it becomes a better and better approximation for $$1 – e^{-P}$$, which for the example above is 0.551. Hey, 60 fps is pretty accurate — it’s just accurately representing something nowhere near what I wanted. Er, you wanted.)

### Rolling your own

Of course, you can fuss with the classic [0, 1] uniform value however you want. If I want a bias towards zero, I’ll often just square it, or multiply two of them together. If I want a bias towards one, I’ll take a square root. If I want something like a Gaussian/normal distribution, but with clearly-defined endpoints, I might add together n rolls and divide by n. (The normal distribution is just what you get if you roll infinite dice and divide by infinity!)

It’d be nice to be able to understand exactly what this will do to the distribution. Unfortunately, that requires some calculus, which this post is too small to contain, and which I didn’t even know much about myself until I went down a deep rabbit hole while writing, and which in many cases is straight up impossible to express directly.

Here’s the non-calculus bit. A source of randomness is often graphed as a PDF — a probability density function. You’ve almost certainly seen a bell curve graphed, and that’s a PDF. They’re pretty nice, since they do exactly what they look like: they show the relative chance that any given value will pop out. On a bog standard bell curve, there’s a peak at zero, and of course zero is the most common result from a normal distribution.

(Okay, actually, since the results are continuous, it’s vanishingly unlikely that you’ll get exactly zero — but you’re much more likely to get a value near zero than near any other number.)

For the uniform distribution, which is what a classic rand() gives you, the PDF is just a straight horizontal line — every result is equally likely.

If there were a calculus bit, it would go here! Instead, we can cheat. Sometimes. Mathematica knows how to work with probability distributions in the abstract, and there’s a free web version you can use. For the example of squaring a uniform variable, try this out:

 1 PDF[TransformedDistribution[u^2, u \[Distributed] UniformDistribution[{0, 1}]], u] 

(The \[Distributed] is a funny tilde that doesn’t exist in Unicode, but which Mathematica uses as a first-class operator. Also, press shiftEnter to evaluate the line.)

This will tell you that the distribution is… $$\frac{1}{2\sqrt{u}}$$. Weird! You can plot it:

 1 Plot[%, {u, 0, 1}] 

(The % refers to the result of the last thing you did, so if you want to try several of these, you can just do Plot[PDF[…], u] directly.)

The resulting graph shows that numbers around zero are, in fact, vastly — infinitely — more likely than anything else.

What about multiplying two together? I can’t figure out how to get Mathematica to understand this, but a great amount of digging revealed that the answer is -ln x, and from there you can plot them both on Wolfram Alpha. They’re similar, though squaring has a much better chance of giving you high numbers than multiplying two separate rolls — which makes some sense, since if either of two rolls is a low number, the product will be even lower.

What if you know the graph you want, and you want to figure out how to play with a uniform roll to get it? Good news! That’s a whole thing called inverse transform sampling. All you have to do is take an integral. Good luck!

This is all extremely ridiculous. New tactic: Just Simulate The Damn Thing. You already have the code; run it a million times, make a histogram, and tada, there’s your PDF. That’s one of the great things about computers! Brute-force numerical answers are easy to come by, so there’s no excuse for producing something like rnz. (Though, be sure your histogram has sufficiently narrow buckets — I tried plotting one for rnz once and the weird stuff on the left side didn’t show up at all!)

By the way, I learned something from futzing with Mathematica here! Taking the square root (to bias towards 1) gives a PDF that’s a straight diagonal line, nothing like the hyperbola you get from squaring (to bias towards 0). How do you get a straight line the other way? Surprise: $$1 – \sqrt{1 – u}$$.

### Okay, okay, here’s the actual math

I don’t claim to have a very firm grasp on this, but I had a hell of a time finding it written out clearly, so I might as well write it down as best I can. This was a great excuse to finally set up MathJax, too.

Say $$u(x)$$ is the PDF of the original distribution and $$u$$ is a representative number you plucked from that distribution. For the uniform distribution, $$u(x) = 1$$. Or, more accurately,

$$u(x) = \begin{cases} 1 & \text{ if } 0 \le x \lt 1 \\ 0 & \text{ otherwise } \end{cases}$$

Remember that $$x$$ here is a possible outcome you want to know about, and the PDF tells you the relative probability that a roll will be near it. This PDF spits out 1 for every $$x$$, meaning every number between 0 and 1 is equally likely to appear.

We want to do something to that PDF, which creates a new distribution, whose PDF we want to know. I’ll use my original example of $$f(u) = u^2$$, which creates a new PDF $$v(x)$$.

The trick is that we need to work in terms of the cumulative distribution function for $$u$$. Where the PDF gives the relative chance that a roll will be (“near”) a specific value, the CDF gives the relative chance that a roll will be less than a specific value.

The conventions for this seem to be a bit fuzzy, and nobody bothers to explain which ones they’re using, which makes this all the more confusing to read about… but let’s write the CDF with a capital letter, so we have $$U(x)$$. In this case, $$U(x) = x$$, a straight 45° line (at least between 0 and 1). With the definition I gave, this should make sense. At some arbitrary point like 0.4, the value of the PDF is 1 (0.4 is just as likely as anything else), and the value of the CDF is 0.4 (you have a 40% chance of getting a number from 0 to 0.4).

Calculus ahoy: the PDF is the derivative of the CDF, which means it measures the slope of the CDF at any point. For $$U(x) = x$$, the slope is always 1, and indeed $$u(x) = 1$$. See, calculus is easy.

Okay, so, now we’re getting somewhere. What we want is the CDF of our new distribution, $$V(x)$$. The CDF is defined as the probability that a roll $$v$$ will be less than $$x$$, so we can literally write:

$$V(x) = P(v \le x)$$

(This is why we have to work with CDFs, rather than PDFs — a PDF gives the chance that a roll will be “nearby,” whatever that means. A CDF is much more concrete.)

What is $$v$$, exactly? We defined it ourselves; it’s the do something applied to a roll from the original distribution, or $$f(u)$$.

$$V(x) = P\!\left(f(u) \le x\right)$$

Now the first tricky part: we have to solve that inequality for $$u$$, which means we have to do something, backwards to $$x$$.

$$V(x) = P\!\left(u \le f^{-1}(x)\right)$$

Almost there! We now have a probability that $$u$$ is less than some value, and that’s the definition of a CDF!

$$V(x) = U\!\left(f^{-1}(x)\right)$$

Hooray! Now to turn these CDFs back into PDFs, all we need to do is differentiate both sides and use the chain rule. If you never took calculus, don’t worry too much about what that means!

$$v(x) = u\!\left(f^{-1}(x)\right)\left|\frac{d}{dx}f^{-1}(x)\right|$$

Wait! Where did that absolute value come from? It takes care of whether $$f(x)$$ increases or decreases. It’s the least interesting part here by far, so, whatever.

There’s one more magical part here when using the uniform distribution — $$u(\dots)$$ is always equal to 1, so that entire term disappears! (Note that this only works for a uniform distribution with a width of 1; PDFs are scaled so the entire area under them sums to 1, so if you had a rand() that could spit out a number between 0 and 2, the PDF would be $$u(x) = \frac{1}{2}$$.)

$$v(x) = \left|\frac{d}{dx}f^{-1}(x)\right|$$

So for the specific case of modifying the output of rand(), all we have to do is invert, then differentiate. The inverse of $$f(u) = u^2$$ is $$f^{-1}(x) = \sqrt{x}$$ (no need for a ± since we’re only dealing with positive numbers), and differentiating that gives $$v(x) = \frac{1}{2\sqrt{x}}$$. Done! This is also why square root comes out nicer; inverting it gives $$x^2$$, and differentiating that gives $$2x$$, a straight line.

Incidentally, that method for turning a uniform distribution into any distribution — inverse transform sampling — is pretty much the same thing in reverse: integrate, then invert. For example, when I saw that taking the square root gave $$v(x) = 2x$$, I naturally wondered how to get a straight line going the other way, $$v(x) = 2 – 2x$$. Integrating that gives $$2x – x^2$$, and then you can use the quadratic formula (or just ask Wolfram Alpha) to solve $$2x – x^2 = u$$ for $$x$$ and get $$f(u) = 1 – \sqrt{1 – u}$$.

Multiply two rolls is a bit more complicated; you have to write out the CDF as an integral and you end up doing a double integral and wow it’s a mess. The only thing I’ve retained is that you do a division somewhere, which then gets integrated, and that’s why it ends up as $$-\ln x$$.

And that’s quite enough of that! (Okay but having math in my blog is pretty cool and I will definitely be doing more of this, sorry, not sorry.)

## Random vs varied

Sometimes, random isn’t actually what you want. We tend to use the word “random” casually to mean something more like chaotic, i.e., with no discernible pattern. But that’s not really random. In fact, given how good humans can be at finding incidental patterns, they aren’t all that unlikely! Consider that when you roll two dice, they’ll come up either the same or only one apart almost half the time. Coincidence? Well, yes.

If you ask for randomness, you’re saying that any outcome — or series of outcomes — is acceptable, including five heads in a row or five tails in a row. Most of the time, that’s fine. Some of the time, it’s less fine, and what you really want is variety. Here are a couple examples and some fairly easy workarounds.

### NPC quips

The nature of games is such that NPCs will eventually run out of things to say, at which point further conversation will give the player a short brush-off quip — a slight nod from the designer to the player that, hey, you hit the end of the script.

Some NPCs have multiple possible quips and will give one at random. The trouble with this is that it’s very possible for an NPC to repeat the same quip several times in a row before abruptly switching to another one. With only a few options to choose from, getting the same option twice or thrice (especially across an entire game, which may have numerous NPCs) isn’t all that unlikely. The notion of an NPC quip isn’t very realistic to start with, but having someone repeat themselves and then abruptly switch to something else is especially jarring.

The easy fix is to show the quips in order! Paradoxically, this is more consistently varied than choosing at random — the original “order” is likely to be meaningless anyway, and it already has the property that the same quip can never appear twice in a row.

If you like, you can shuffle the list of quips every time you reach the end, but take care here — it’s possible that the last quip in the old order will be the same as the first quip in the new order, so you may still get a repeat. (Of course, you can just check for this case and swap the first quip somewhere else if it bothers you.)

That last behavior is, in fact, the canonical way that Tetris chooses pieces — the game simply shuffles a list of all 7 pieces, gives those to you in shuffled order, then shuffles them again to make a new list once it’s exhausted. There’s no avoidance of duplicates, though, so you can still get two S blocks in a row, or even two S and two Z all clumped together, but no more than that. Some Tetris variants take other approaches, such as actively avoiding repeats even several pieces apart or deliberately giving you the worst piece possible.

### Random drops

Random drops are often implemented as a flat chance each time. Maybe enemies have a 5% chance to drop health when they die. Legally speaking, over the long term, a player will see health drops for about 5% of enemy kills.

Over the short term, they may be desperate for health and not survive to see the long term. So you may want to put a thumb on the scale sometimes. Games in the Metroid series, for example, have a somewhat infamous bias towards whatever kind of drop they think you need — health if your health is low, missiles if your missiles are low.

I can’t give you an exact approach to use, since it depends on the game and the feeling you’re going for and the variables at your disposal. In extreme cases, you might want to guarantee a health drop from a tough enemy when the player is critically low on health. (Or if you’re feeling particularly evil, you could go the other way and deny the player health when they most need it…)

The problem becomes a little different, and worse, when the event that triggers the drop is relatively rare. The pathological case here would be something like a raid boss in World of Warcraft, which requires hours of effort from a coordinated group of people to defeat, and which has some tiny chance of dropping a good item that will go to only one of those people. This is why I stopped playing World of Warcraft at 60.

Dialing it back a little bit gives us Enter the Gungeon, a roguelike where each room is a set of encounters and each floor only has a dozen or so rooms. Initially, you have a 1% chance of getting a reward after completing a room — but every time you complete a room and don’t get a reward, the chance increases by 9%, up to a cap of 80%. Once you get a reward, the chance resets to 1%.

The natural question is: how frequently, exactly, can a player expect to get a reward? We could do math, or we could Just Simulate The Damn Thing.

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 from collections import Counter import random histogram = Counter() TRIALS = 1000000 chance = 1 rooms_cleared = 0 rewards_found = 0 while rewards_found < TRIALS: rooms_cleared += 1 if random.random() * 100 < chance: # Reward! rewards_found += 1 histogram[rooms_cleared] += 1 rooms_cleared = 0 chance = 1 else: chance = min(80, chance + 9) for gaps, count in sorted(histogram.items()): print(f"{gaps:3d} | {count / TRIALS * 100:6.2f}%", '#' * (count // (TRIALS // 100))) 
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15  1 | 0.98% 2 | 9.91% ######### 3 | 17.00% ################ 4 | 20.23% #################### 5 | 19.21% ################### 6 | 15.05% ############### 7 | 9.69% ######### 8 | 5.07% ##### 9 | 2.09% ## 10 | 0.63% 11 | 0.12% 12 | 0.03% 13 | 0.00% 14 | 0.00% 15 | 0.00% 

We’ve got kind of a hilly distribution, skewed to the left, which is up in this histogram. Most of the time, a player should see a reward every three to six rooms, which is maybe twice per floor. It’s vanishingly unlikely to go through a dozen rooms without ever seeing a reward, so a player should see at least one per floor.

Of course, this simulated a single continuous playthrough; when starting the game from scratch, your chance at a reward always starts fresh at 1%, the worst it can be. If you want to know about how many rewards a player will get on the first floor, hey, Just Simulate The Damn Thing.

 1 2 3 4 5 6 7  0 | 0.01% 1 | 13.01% ############# 2 | 56.28% ######################################################## 3 | 27.49% ########################### 4 | 3.10% ### 5 | 0.11% 6 | 0.00% 

Cool. Though, that’s assuming exactly 12 rooms; it might be worth changing that to pick at random in a way that matches the level generator.

(Enter the Gungeon does some other things to skew probability, which is very nice in a roguelike where blind luck can make or break you. For example, if you kill a boss without having gotten a new gun anywhere else on the floor, the boss is guaranteed to drop a gun.)

### Critical hits

I suppose this is the same problem as random drops, but backwards.

Say you have a battle sim where every attack has a 6% chance to land a devastating critical hit. Presumably the same rules apply to both the player and the AI opponents.

Consider, then, that the AI opponents have exactly the same 6% chance to ruin the player’s day. Consider also that this gives them an 0.4% chance to critical hit twice in a row. 0.4% doesn’t sound like much, but across an entire playthrough, it’s not unlikely that a player might see it happen and find it incredibly annoying.

Perhaps it would be worthwhile to explicitly forbid AI opponents from getting consecutive critical hits.

## In conclusion

An emerging theme here has been to Just Simulate The Damn Thing. So consider Just Simulating The Damn Thing. Even a simple change to a random value can do surprising things to the resulting distribution, so unless you feel like differentiating the inverse function of your code, maybe test out any non-trivial behavior and make sure it’s what you wanted. Probability is hard to reason about.

# 2017-12-25 равносметка

Post Syndicated from Vasil Kolev original https://vasil.ludost.net/blog/?p=3372

Седя и си мисля за писането равносметка за годината…

В някакъв ред, какво се случи тая година:

– Роди се Ба’ал (официално известен като Игнат);
– Направихме OpenFest 2017, който въпреки новото място мина доста по-лесно;
(write-up-а за мрежата му се надявам да го изкарам тая година)
– Основа се “Да, България” (на която съм член);
– Избута се и FOSDEM 2017 (и следва 2018, където даже ще водя звяра);
Ожених се;
– Омъжихме и Яна, и разни други хора (май се събраха три сватби тая година);
– Почнах работа в StorPool (и сега интервюирам повече за админи, отколкото за developer-и, и всеки ден откривам как нещо от света около мен не работи);
– Свършихме някакви неща с лаба, като последното е да си имаме podcast студио (в което може да запишем тая година един лабов такъв);
– С Мариян си взехме половин rack в 3DC и си събрахме техниката на едно място, с наш ASN и връзки. Някой ден трябва да го разпиша по-подробно;
– Организирах/правих/помагах в stream-ването и видеото на поне 10 събития;
– Почина най-малката ми братовчедка.

Имам един файл, който е в git и в който си пиша какво имам да правя (нещо като календар, ама допотопен), и май не съм имал много време да си почивам тая година. Може да се опитам догодина…

# HackSpace magazine 2: 3D printing and cheese making

Post Syndicated from Andrew Gregory original https://www.raspberrypi.org/blog/hackspace-magazine-issue-2/

After an incredible response to our first issue of HackSpace magazine last month, we’re excited to announce today’s release of issue 2, complete with cheese making, digital braille, and…a crochet Cthulhu?

This issue, we visit Swansea Hackspace to learn how to crochet, we hear about the superb things that Birmingham’s fizzPOP maker space is doing, and we’re extremely impressed by the advances in braille reader technology that are coming out of Bristol Hackspace. People are amazing.

We’ve also collected page upon page of projects for you to try your hand at. Fancy an introduction to laser cutting? A homemade sine wave stylophone? Or how about our first foray into Adafruit’s NeoPixels, adding blinkenlights to a pair of snowboarding goggles?

And (much) older technology gets a look in too, including a tutorial showing you how to make a knife in your own cheap and cheerful backyard forge.

As always, issue 2 of HackSpace magazine is available as a free PDF download, but we’ll also be publishing online versions of selected articles for easier browsing, so be sure to follow us on Facebook and Twitter. And, of course, we want to hear your thoughts – contact us to let us know what you like and what else you’d like to see, or just to demand that we feature your project, interest or current curiosity in the next issue.

You can grab issue 2 of HackSpace magazine right now from WHSmith, Tesco, Sainsbury’s, and independent newsagents. If you live in the US, check out your local Barnes & Noble, Fry’s, or Micro Center next week. We’re also shipping to stores in Australia, Hong Kong, Canada, Singapore, Belgium, and Brazil, so be sure to ask your local newsagent whether they’ll be getting HackSpace magazine.

Alternatively, you can get the new issue online from our store, or digitally via our Android or iOS apps. And don’t forget, as with all our publications, a free PDF of HackSpace magazine is available from release day.

That’s it from us for this year; see you in 2018 for a ton of new things to make and do!

The post HackSpace magazine 2: 3D printing and cheese making appeared first on Raspberry Pi.

# The deep learning Santa/Not Santa detector

Post Syndicated from Alex Bate original https://www.raspberrypi.org/blog/deep-learning-santa-detector/

Did you see Mommy kissing Santa Claus? Or was it simply an imposter? The Not Santa detector is here to help solve the mystery once and for all.

#### Building a “Not Santa” detector on the Raspberry Pi using deep learning, Keras, and Python

The video is a demo of my “Not Santa” detector that I deployed to the Raspberry Pi. I trained the detector using deep learning, Keras, and Python. You can find the full source code and tutorial here: https://www.pyimagesearch.com/2017/12/18/keras-deep-learning-raspberry-pi/

## Ho-ho-how does it work?

Note: Adrian Rosebrock is not Santa. But he does a good enough impression of the jolly old fellow that his disguise can fool a Raspberry Pi into thinking otherwise.

We jest, but has anyone seen Adrian and Santa in the same room together?

But how is the Raspberry Pi able to detect the Santa-ness or Not-Santa-ness of people who walk into the frame?

### Two words: deep learning

If you’re not sure what deep learning is, you’re not alone. It’s a hefty topic, and one that Adrian has written a book about, so I grilled him for a bluffers’ guide. In his words, deep learning is:

…a subfield of machine learning, which is, in turn a subfield of artificial intelligence (AI). While AI embodies a large, diverse set of techniques and algorithms related to automatic reasoning (inference, planning, heuristics, etc), the machine learning subfields are specifically interested in pattern recognition and learning from data.

Artificial Neural Networks (ANNs) are a class of machine learning algorithms that can learn from data. We have been using ANNs successfully for over 60 years, but something special happened in the past 5 years — (1) we’ve been able to accumulate massive datasets, orders of magnitude larger than previous datasets, and (2) we have access to specialized hardware to train networks faster (i.e., GPUs).

Given these large datasets and specialized hardware, deeper neural networks can be trained, leading to the term “deep learning”.

So now we have a bird’s-eye view of deep learning, how does the detector detect?

### Cameras and twinkly lights

Adrian used a model he had trained on two datasets to detect whether or not an image contains Santa. He deployed the Not Santa detector code to a Raspberry Pi, then attached a camera, speakers, and The Pi Hut’s 3D Xmas Tree.

Components for Santa detection

The camera captures footage of Santa in the wild, while the Christmas tree add-on provides a twinkly notification, accompanied by a resonant ho, ho, ho from the speakers.

### A deeper deep dive into deep learning

A full breakdown of the project and the workings of the Not Santa detector can be found on Adrian’s blog, PyImageSearch, which includes links to other deep learning and image classification tutorials using TensorFlow and Keras. It’s an excellent place to start if you’d like to understand more about deep learning.

## Build your own Santa detector

Santa might catch on to Adrian’s clever detector and start avoiding the camera, and for that eventuality, we have our own Santa detector. It uses motion detection to notify you of his presence (and your presents!).

Check out our Santa Detector resource here and use a passive infrared sensor, Raspberry Pi, and Scratch to catch the big man in action.

The post The deep learning Santa/Not Santa detector appeared first on Raspberry Pi.

# Weekly roundup: Invinco Beat

Post Syndicated from Eevee original https://eev.ee/dev/2017/12/18/weekly-roundup-invinco-beat/

I’ve been a bit all over the place! And I’m starting to go nocturnal again, oh no.

• art: I started drawing a header image for my itch.io page, which for a year now has been barren, save for a promise that I would soon make it unbarren.

I accidentally spent a good chunk of time toodling around with 3D modelling again, this time trying to aim for low-poly with pixel art textures. I tried a couple things, but the biggest success by far was Star Anise.

• anise!!: Still not done, but asymptotically approaching done. Most of the time has been going towards the map, which has been rearchitectued several times, and which is bigger and more complicated than anything we’ve done before. Also did some regular old mechanical stuff, like doors and whatnot.

• misc: I had MegaZeux on the brain and wanted to try out the Web Audio API, so on a total whim I wrote a little player for MegaZeux’s SFX strings.