%% title = "tairu - an interactive exploration of 2D autotiling techniques" scripts = [ "tairu/cardinal-directions.js", "tairu/framework.js", "tairu/tairu.js", "tairu/tilemap-registry.js", ] styles = ["tairu.css"] % id = "01HPD4XQPWM8ECT2QM6AT9YRWB" - I remember since my early days doing programming, I've been interested in how games like Terraria handle automatically tiling their terrain. % id = "01HPD4XQPWPDBH6QQAZER7A05G" - in Terraria, you can fully modify the terrain however you want, and the tiles will connect to each other seamlessly. % id = "01HPD4XQPW8HE7681P7H686X4N" - TODO: short videos demoing this here % id = "01HPD4XQPWJBTJ4DWAQE3J87C9" - once upon a time I heard of a technique called...\ **bitwise autotiling** % id = "01HPD4XQPW6VK3FDW5QRCE6HSS" + I learned about it back when I was building 2D Minecraft clones using [Construct 2](https://www.construct.net/en/construct-2/manuals/construct-2), and I wanted my terrain to look nice as it does in Terraria % id = "01HPD4XQPWJ1CE9ZVRW98X7HE6" - Construct 2 was one of my first programming experiences and the first game engine I truly actually liked :smile: % id = "01HPJ8GHDET8ZGNN0AH3FWA8HX" - let's begin with a tilemap. say we have the following grid of tiles: (the examples are interactive, try editing it!) Your browser does not support <canvas>. % id = "01HPJ8GHDEC0Z334M04MTNADV9" - for each tile, we can assign a bitset of cardinal directions like so: Your browser does not support <canvas>. % template = true id = "01HPJ8GHDE9QKQ4QFZK1Z1KQD4" classes.branch = "tileset-cardinal-directions-demo" + now given a tileset, such as the one below that I drew a while ago, we can assign each tile to a set of cardinal directions. I'll indicate where there's a connection between individual tiles with the letters **N**, **E**, **S**, **W**, standing for the cardinal directions **N**orth, **E**ast, **S**outh, and **W**est. % id = "01HPMVT9BM65YD5AXWPT4Z67H5" - (it's frustratingly hard to center individual letters like this in CSS. please forgive me for how crooked these are!) % id = "01HPMVT9BM5V4BP8K80X0C1HJZ" - note that the state of connection for a given cardinal direction can be represented using two values: **connected**, and **not connected**. two values make one bit, so we can pack these four connection states into four bits, and use that as an array index! % classes.branch = "tileset-cardinal-directions-demo" id = "01HPMVT9BM4AXG2Z1D2QBH828G" + for that to work though, we need to rearrange our tilemap somewhat such that we can index into it easily using our integer. assuming we pack our bits as `NWSE` (bit 0 is east, each next bit we go clockwise), therefore the final arrangement is this:
E S ES W EW SW ESW N EN SN ESN WN EWN SWN ESWN
packing that into a single tilesheet, or rather tile *strip*, we get this image: ![horizontal tile strip of 16 8x8 pixel metal tiles][pic:01HPMMR6DGKYTPZ9CK0WQWKNX5] % id = "01HPMVT9BMMEM4HT4ANZ40992P" - in JavaScript, drawing on a `` using bitwise autotiling would look like this: ```javascript for (let y = 0; y < tilemap.height; ++y) { for (let x = 0; x < tilemap.width; ++x) { // Assume `tilemap.at` is a function which returns the type of tile // stored at coordinates (x, y). let tile = tilemap.at(x, y); // We need to treat *some* tile as an empty (fully transparent) tile. // In our case that'll be 0. if (tile != 0) { let tileset = tilesets[tile]; // Now it's time to represent the tile connections as bits. // For each cardinal direction we produce a different bit value, or 0 if there is // no connection: let connectedWithEast = shouldConnect(tile, tilemap.at(x + 1, y)) ? 0b0001 : 0; let connectedWithSouth = shouldConnect(tile, tilemap.at(x, y + 1)) ? 0b0010 : 0; let connectedWithWest = shouldConnect(tile, tilemap.at(x - 1, y)) ? 0b0100 : 0; let connectedWithNorth = shouldConnect(tile, tilemap.at(x, y - 1)) ? 0b1000 : 0; // Then we OR them together into one integer. let tileIndex = connectedWithNorth | connectedWithWest | connectedWithSouth | connectedWithEast; // With that, we can draw the correct tile. // Our strip is a single horizontal line, so we can assume let tilesetTileSize = tileset.height; let tilesetX = tileIndex * tilesetTileSize; let tilesetY = 0; ctx.drawImage( tilesets[tile], tilesetX, tilesetY, tilesetTileSize, tilesetTileSize, x * tileSize, y * tileSize, tileSize, tileSize, ); } } } ``` % template = true id = "01HPMVT9BM9CS9375MX4H9WKW8" - and that gives us this result: Your browser does not support <canvas>. % id = "01HPMVT9BM3WR0BNZFHP2BPZ8A" - but if you play around with it (or have *already* played around with it, and are therefore left with a non-default tilemap) ...something seems awful about it doesn't it? % template = true id = "01HPMVT9BMPA89037VPWPPWX8V" - something's off about the corners. let me give you a fresh example to illustrate what I mean: Your browser does not support <canvas>. % id = "01HPMVT9BM16EF3TV5J1K19JAM" + see that tile in the bottom left corner of the `L` shape? it's missing a corner. the top-right corner, to be exact, which makes it visually disjoint from the tiles to the north and the east. % id = "01HPMVT9BM5VWJSMDNPK2SRNZV" - (I'm totally not trying to say this implementation is an L so far) % id = "01HPMVT9BMWG6QHQ125Z884W8Z" + i'll cut right to the chase here and say it outright - the issue is that we simply don't have enough tiles to represent corner cases like this! % id = "01HPMVT9BMQK8N1H68YV3J4CFQ" - see what I did there? % id = "01HPMVT9BMJTG3KD3K5EJ3BC93" - the solution here is to introduce more tiles to handle these edge cases. TODO Explain % id = "01HPD4XQPWT9N8X9BD9GKWD78F" - bitwise autotiling is a really cool technique that I've used in plenty of games in the past % id = "01HPD4XQPW5FQY8M04S6JEBDHQ" - as I mentioned before, [I've known it since my Construct 2 days][branch:01HPD4XQPW6VK3FDW5QRCE6HSS], but when it comes to my released games [Planet Overgamma] would probably be the first to utilize it properly TODO video of some Planet Overgamma gameplay showing the autotiling in action [Planet Overgamma]: https://liquidev.itch.io/planet-overgamma-classic % id = "01HPJ8GHDEN4XRPT1AJ1BTNTFJ" - this accursed game has been haunting me for years since; there have been many iterations. he autotiling source code of the one in the video can be found [here][autotiling source code]. [autotiling source code]: https://github.com/liquidev/planet-overgamma/blob/classic/jam/map.lua#L209 % id = "01HPD4XQPWPN6HNA6M6EH507C6" + but one day I found a really cool project called [Tilekit](https://rxi.itch.io/tilekit) % id = "01HPD4XQPW11EQTBDQSGXW3S52" + (of course it's really cool, after all rxi made it) % id = "01HPD4XQPWYHS327BV586SB085" - for context rxi is the genius behind the Lua-powered, simple, and modular text editor `lite` that I was using for quite a while % id = "01HPD4XQPWJ9QAQ5MF2J5JBB8M" - after a while I switched to a fork - Lite XL, which had better font rendering and more features % id = "01HPD4XQPWB11TZSX5VAAJ6TCD" - I stopped using it because VS Code was just more feature packed and usable; no need to reinvent the wheel, rust-analyzer *just works.* % id = "01HPD4XQPW3G7BXTBBTD05MB8V" - the LSP plugin for Lite XL had some issues around autocompletions not filling in properly :pensive:\ it's likely a lot better now, but back then I decided this is too much for my nerves. while tinkering with your editor is something really cool, in my experience it's only cool up to a point. % id = "01HPD4XQPWV1BAPA27SNDFR93B" - the cool thing with Tilekit is that it's *more* than just your average bitwise autotiling - of course it *can* do basic autotiling, but it can also do so much more % id = "01HPD4XQPWM1JSAPXVT6NBHKYY" classes.branch_children = "branch-quote" - if I had to describe it, it's basically something of a *shader langauge for tilesets.* this makes it really powerful, as you can do little programs like % id = "01HPD4XQPWE7ZVR0SS67DHTGHQ" - autotile using this base tileset % id = "01HPD4XQPW2BFZYQQ920SYHM9M" - if the tile above is empty AND with a 50% chance % id = "01HPD4XQPWJB7V67TS1M3HFCYE" - then grass % id = "01HPD4XQPWF7K85Z0CEK4WDDBZ" - if the tile above is solid AND with a 10% chance % id = "01HPD4XQPW5J3N6MVT9Z2W00S9" - then vines % id = "01HPD4XQPWGCMCEAR5Z9EETSGP" - if the tile above is vines AND with a 50% chance % id = "01HPD4XQPWP847T0EAM0FJ88T4" - then vines % id = "01HPD4XQPWK58Z63X6962STADR" - I mean, after all - bitwise autotiling is basically a clever solution to an `if` complexity problem, so why not extend that with more logic and rules and stuff to let you build more complex maps? % id = "01HPJ8GHDFRA2SPNHKJYD0SYPP" - of course Tilekit's solution is a lot more simple, streamlined, and user-friendly, but you get the gist. % id = "01HPD4XQPW4Y075XWJCT6AATB2" - ever since then I've been wanting to build something just like Tilekit, but in the form of an educational, interactive blog post to demonstrate the ideas in a fun way % id = "01HPD4XQPWR8J9WCNBNCTJERZS" - and what you're reading is the result of that. % id = "01HPD4XQPW1EP8YHACRJVMA0GM" - so let's get going! first, we'll build a basic tile editor using JavaScript. % id = "01HPD4XQPWPNRTVJFNFGNHJMG1" + not my favorite language, but we're on the Web so it's not like we have much more of a choice. % id = "01HPD4XQPWGK7M4XJYC99XE4T6" - I could use TypeScript, but this page follows a philosophy of not introducing complexity where I can deal without it. TypeScript is totally cool, but not necessary. % id = "01HPD4XQPWAE0ZH46WME6WJSVP" - I'll be using Web Components (in particular, custom elements) combined with canvas to add stuff onto the page.