Monday, May 15, 2017

WallyFOV: Shadow-casting field-of-view implementation with walls


I've been working on a field-of-view algorithm for 2d tile-based games (e.g. roguelikes).  There's a particular killer feature I mean to include in the algorithm, which I won't reveal in this post, but I decided to go ahead and release the slightly simpler version because I think it might be useful on its own.

It's called WallyFOV.  It's basically an implementation of recursive shadowcasting in TypeScript, but with support for walls.

Go ahead and check out the demo.  (and thanks to EasyStar.js for the pathfinding algorithm used in that demo, and from which I kindof copied the demo page style)

Recursive shadowcasting works by scanning outwards from the player looking for obstructions.  When something is found, a shadow (represented by two angles) is added to a shadow list.  Overlapping shadows are merged to keep the algorithm running quickly.

In this particular variant, a tile is considered visible if there exists any line from the center of the player's tile to any point within the target tile.  There are some complications around dealing with diagonally-adjacent bodies, which you can read about in the algorithm overview, but overall it's a pretty simple algorithm to understand.  It's a bit tricky to implement and optimize, however.

I spent a little extra time optimizing it to run in V8 (at least the version of V8 in node.js 7.9).  Along the way I learned how to use node's --trace-deopt, and discovered some very unexpected optimization tips, mainly having to do with newer ECMAScript features.

For instance, this version of V8 doesn't optimize "compound let/const assignment".  Meaning if you declare a variable with let or const, and then use something like X += Y, your function will be deoptimized.  Simply using X = X + Y instead avoids that trap.  The general lesson here is that JavaScript is apparently changing too rapidly to rely on the engine optimizing things according to your intuition.  This is probably true with any language, to a certain extent.  But, come on, X = X + Y?


Friday, January 27, 2017

Two Songs Arranged for Solo Piano

I've arranged two of my songs for solo piano, using MuseScore.  I had to make some changes in these arrangements compared to the originals, to remove or combine parts, and to make them physically possible to play.  I'm not a great pianist, but I made sure that I could play them through at a stop-and-think-about-the-next-part pace.  I think someone more skilled should be able to play them properly.

If you're that person I'd love to hear the result.  You can use the Download link at the MuseScore page for each piece to get printable versions of the scores.


The easier of the two, this one involves lots of many-fingered chords in both the right and left hands.  It's a mellow, ambient piece, and my most recent.


I made this one for Robot Quest.  At the time I called it "Plugged In", but I've renamed it because this name is much better.  A quick, boisterous, staccato piece, this one is very hard for me to play.

Sunday, December 18, 2016

Kendall Stories

Lala and Sing acting out an argument.
Here are some web animations I made for my daughter.  One day she asked me to cut a hole out of a cardboard box so she could use it as a TV.  She then made three "shows", and for each one she drew scenes on several sheets of paper.  To present the shows, she would hold the paper up to the hole in the box while the rest of us sat on the other side and watched.

I thought it would be cute to turn her drawings into SVG images and animate them, and to record her voice and sync it up with the animation.  She really got into it, giving me very strict directorial instructions.  Part of the challenge for me was to try not to "improve" on her work with my own ideas.  I tried to stay as true to her vision for the shows as possible, and I included all of her mistakes (that she didn't catch in post-production and demand that I fix).

Not gonna what?

I used GreenSock GSAP's TweenMax library for the animations, and howler.js for audio.  Both are overpowered for this kind of project, but they saved time that I would have spent dealing with little headaches.  For instance you can't trigger HTML5 audio directly on mobile browsers.  I should have found a library for preloading and sizing images, because I ended up with some frustrating work making sure image sizes were loaded properly for IE.



Sunday, November 27, 2016

Word Search Generator

Here's a quickly-slapped-together little project that generates word search puzzles.

I've been kicking around an idea for a kind of "evil" word search, in which there are tons of letter combinations that almost spell words, but don't.  The trick would be to see how distracting the almost-words are, and whether that makes the correctly-spelled words harder to find.  That's not what this one is, though.  This one is just a regular, non-evil word search generator.

The core generator code is at this githib repo, or on npm as @sbj42/word-search-generator.

Sunday, November 20, 2016

Mr. Floppypants

Here's Mr. Floppypants.  A simple ragdoll-physics game.  Maybe it's about a very lazy person who needs to be forced to go explore and have fun.

It's based loosely on a "Chrome experiment" called Boingy, which the kids really got a kick out of.  I think they mostly liked dropping stuff on the poor protagonist, or forcing it to fall down stairs, or getting it twisted up into painful-looking poses.  After I played a bunch of MANYGOLF and through that learned about the p2.js javascript physics engine, I thought I'd make a more complicated version of my own.

It seems to work in Chome, Firefox, and Edge.  It does not work in IE.

Basically you click and drag to toss the guy around.  For more advanced play, if you click on his hand and drag it to something then he'll "grab" the thing.  You can use this to carry an item with you to some other part of the world, and to operate the car.


This game isn't nearly finished yet.  I was hoping to make the world a lot larger, and to add other characters to meet and also toss around.  If you get any ideas for things I could add to the game, let me know in the comments below.



Tuesday, October 18, 2016

Song: Coming Up for Air

I was trying to make some background music for It's EELectric!, but I failed.  I had various ideas, mostly working around an undersea theme.  I originally wanted something like the "Evan's Room" song from Legend of Zelda: Majora's Mask.  (digression: I always associated that song with being underwater because that's the context in which you hear it in the game, but I just learned from Zeldapedia that it's also the "Game Over" music from the original Legend of Zelda.)

Anyway after various ideas didn't seem to work, I settled on a sequence of 9th chords.  I expanded that into a more complete piece with a solemn, contemplative verse and a hopeful chorus.  Then I realized that it didn't at all fit the whimsical theme of the game for which I was writing it, and completely gave up on using it in that context.


Now I don't have anything to attach it to, so here it is by itself:


Friday, October 14, 2016

Maze generators

I'm working on another game for the kids, called "Mr. Floppypants", of which I'll say no more in this article, except that I'm using node.js, and that for it I required some code to generate a maze.  For once not wanting to write my own code for that particular subfeature, I searched around npm for "maze generator" packages.  There were a few.

Watch out for bull-men!
I set about looking into each one in turn to see if it would suffice, but I discovered for each one a reason not to use it.  One of them simply didn't run, another used Ecmascript 6 (and so wouldn't work in some browsers without being transpiled), one only worked for square mazes, and some (and I admit I was a bit picky) just weren't written to my taste.  Maze generation is a fun little project, and it's natural that many people have made their own generators, in varying degrees of quality.  Yes, I gave up and wrote my own.

Here's what I learned about mazes... wait, no.  Instead let me point you at some much better sources of information:

Jamis Buck writes a mostly-programming blog, and wrote a great series on maze generators in 2010 and 2011.  This in-browser presentation sums up the whole maze generation concept very nicely, and this recap of the blog series is a great place to get more details.  He describes how to implement a handful of algorithms, and provides in-browser demos so you can watch the algorithm run.

Walter Pullen has such a variety of interests that I refuse to summarize his site, in one part of it you can find a very thorough maze generator program he wrote, and he has written extensively about maze generation.  Aalso I just can't keep myself from mentioning his extensive files about the movie Labyrinth.

Now you know everything about mazes.  But just in case you didn't spend hours reading through all that stuff, here are some highlights:

A maze is basically equivalent to a spanning tree of a graph based on a rectangular grid.  Consequently, algorithms that compute spanning trees can be adapted to make mazes.  Kruskal's algorithm is like this, and builds mazes in an seemingly magical way:  It connects random adjacent cells, taking care not to create a loop, until a maze basically appears out of the noise.

Speaking of Kruskal's, the hardest part is quickly deciding whether two adjacent cells are already connected.  It can be done with a disjoint-set forest, and the tricks they use to make that fast (union by rank and path compression) are neat.

One of the simplest algorithms, recursive-backtracking, is my pick for making the best-looking mazes.  While generators like Kruskal's tend to make lots of clustered dead-ends, recursive-backtracking prefers meandering passages.  It works as basically a randomized depth-first-search of the grid.

Eller's algorithm can generate the maze one entire row at a time.  It works by keeping track of which cells connected to the previous row have already been connected (possibly by an earlier, now forgotten row).  On the very last row, it patches up any not-yet-connected regions of the maze.  In doing so, it may end up with a long straight passage along the bottom.

The Aldous-Broder algorithm generates all possible mazes with equal probibility, but you probably don't want to use it because it's very slow.  It's interesting to think about though: Start in a random cell and perform the well-named  "drunkard's walk", digging a passage when (and only when) you walk into a cell you've never visited before.  Assuming you have enough patience, you'll eventually visit every cell and oh hey, there's a maze!

It's not a generator, but "dead end filler" is an amusing way to solve some mazes without ever visiting cells in the solution path.  Find all the dead ends in the maze and fill them in.  Then find any new dead ends you created, and fill those in too.  Repeat until there are no more dead ends.  The remaining unfilled spaces are the solution.

Back to my project:  I implemented three algorithms (recursive-backtracking, modified Prim's, and Kruskal's).  I also used this as an opportunity to learn about node and npm, so the algorithm packages also have unit tests, benchmarks, and demos, and I spent some time trying to optimize them for speed and also make them easy to plug in to another project without needing to bring a lot of dependencies along.


@sbj42/maze-generator npm package

Update (10/15): I added a maze "puzzle" to Probably Puzzles.