add grid and generator

src/app.ts

@@ -1,12 +1,12 @@
-import {fetchPalette, Palette} from "./sprite";
+import {fetchPalette} from "./sprite";
+import {Chunk} from "./chunk";
 
 export class App {
     private canvas: HTMLCanvasElement;
     private readonly context: CanvasRenderingContext2D;
     private lastTime: DOMHighResTimeStamp = 0;
     private isRunning: boolean = false;
-
-    private palette?: Palette;
+    private chunk?: Chunk;
 
     public constructor(canvas: HTMLCanvasElement) {
         this.canvas = canvas;
@@ -19,7 +19,7 @@ export class App {
 
         this.updateSize(window.innerWidth, window.innerHeight);
         window.onresize = () => this.updateSize(window.innerWidth, window.innerHeight);
-        fetchPalette("").then(p => this.palette = p);
+        fetchPalette("").then(palette => this.chunk = new Chunk(palette));
     }
 
     public run() {
@@ -33,14 +33,8 @@ export class App {
 
     private draw(time: DOMHighResTimeStamp) {
         this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
-        if (this.palette) {
-            let x = 0;
-            for (let s of this.palette.sprites) {
-                for (let y = 0; y < 4; y++) {
-                    s.draw(this.context, y * 128, x, y);
-                }
-                x += 128;
-            }
+        if (this.chunk) {
+            this.chunk.render(this.context);
         }
 
         this.lastTime = time;
@@ -56,4 +50,5 @@ export class App {
 }
 
 const app = new App(document.getElementById("render") as HTMLCanvasElement);
+(window as any)._app = app;
 app.run();

src/chunk.ts

@@ -0,0 +1,161 @@
+import { IRender } from "./render";
+import { Direction, Palette, Sprite } from "./sprite";
+
+/** Either a tile (if collapsed), or a list of possible tiles (if not) */
+type MaybeTile = Tile | Tile[];
+
+/** Number of tiles per row and column of a chunk */
+const CHUNK_DIM = 16 >>> 0;
+
+export class Chunk implements IRender {
+    private palette: Palette;
+    private grid: MaybeTile[] = [];
+    private complete: boolean = false;
+
+    public constructor(palette: Palette) {
+        this.palette = palette;
+
+        // pregenerate an array with all possible tiles
+        let allTileVariants = [];
+        for (let s of palette.sprites) {
+            for (let dir = 0; dir < 4; dir++) {
+                allTileVariants.push(new Tile(s, dir));
+            }
+        }
+
+        // initialize the grid with perfect entropy
+        for (let i = 0; i < CHUNK_DIM ** 2; i++) {
+            this.grid.push(allTileVariants);
+        }
+
+        // collapse a single tile to generate an initial disturbance in entropy
+        this.collapseAndUpdate(0, 0);
+
+        window.onmousedown = () => this.tick();
+    }
+
+    public render(context: CanvasRenderingContext2D) {
+        const res = this.palette.resolution;
+        this.grid.forEach((tile, index) => {
+            const y = Math.floor(index / CHUNK_DIM);
+            const x = index % CHUNK_DIM;
+            if (!Array.isArray(tile)) {
+                tile.draw(context, x * res, y * res);
+            }
+        });
+
+        this.tick();
+    }
+
+    private tick() {
+        if (this.complete) {
+            return;
+        }
+
+        let lowest: number = Number.MAX_SAFE_INTEGER;
+        let lowestCoords: number[][] = [];
+        this.grid.forEach((tile, index) => {
+            if (Array.isArray(tile)) {
+                if (tile.length <= lowest) {
+                    const x = index % CHUNK_DIM;
+                    const y = Math.floor(index / CHUNK_DIM);
+                    if (tile.length < lowest) {
+                        lowest = tile.length;
+                        lowestCoords = [[x, y]];
+                    } else {
+                        lowestCoords.push([x, y]);
+                    }
+                }
+            }
+        });
+        if (lowestCoords.length > 0) {
+            let coords = pickRandom(lowestCoords);
+            this.collapseAndUpdate(coords[0], coords[1]);
+        } else {
+            this.complete = true;
+        }
+    }
+
+    /** Collapse a tile and update entropy on surrounding tiles */
+    private collapseAndUpdate(x: number, y: number) {
+        const index = y * CHUNK_DIM + x;
+        const candidates = this.grid[index];
+        if (!Array.isArray(candidates)) {
+            return; // tile is already collapsed (or out of bounds)
+        }
+
+        this.grid[index] = pickRandom(candidates);
+
+        if (y > 0) {
+            this.updateEntropy(x, y - 1); // north
+        }
+        if (x < CHUNK_DIM - 1) {
+            this.updateEntropy(x + 1, y); // east
+        }
+        if (y < CHUNK_DIM - 1) {
+            this.updateEntropy(x, y + 1); // south
+        }
+        if (x > 0) {
+            this.updateEntropy(x - 1, y); // west
+        }
+    }
+
+    /** Remove all candidates that are no longer possible */
+    private updateEntropy(x: number, y: number) {
+        const i = y * CHUNK_DIM + x;
+        const candidates = this.grid[i];
+        if (!Array.isArray(candidates)) {
+            return; // tile is already collapsed (or out of bounds)
+        }
+
+        const filterTile = (tile: MaybeTile) => Array.isArray(tile) ? null : tile;
+        const neighs: (Tile | null)[] = [null, null, null, null];
+        if (y > 0) {
+            neighs[Direction.NORTH] = filterTile(this.grid[i - CHUNK_DIM]);
+        }
+        if (x < CHUNK_DIM - 1) {
+            neighs[Direction.EAST] = filterTile(this.grid[i + 1]);
+        }
+        if (y < CHUNK_DIM - 1) {
+            neighs[Direction.SOUTH] = filterTile(this.grid[i + CHUNK_DIM]);
+        }
+        if (x > 0) {
+            neighs[Direction.WEST] = filterTile(this.grid[i - 1]);
+        }
+
+        // we have to be careful to create an entirely new array here
+        // because the constructor inserts a reference to the same array
+        // of MaybeTiles for every cell, so manipulating the array in-place
+        // would break everything
+        this.grid[i] = candidates.filter(c => !neighs.some((n, dir) => n && c.conflicts(dir, n)));
+    }
+}
+
+export class Tile {
+    private readonly sprite: Sprite;
+    private readonly orientation: Direction;
+
+    public constructor(sprite: Sprite, orientation: Direction) {
+        this.sprite = sprite;
+        this.orientation = orientation;
+    }
+
+    public matches(ownEdge: Direction, neighbor: Tile): boolean {
+        const ownEdgeAbs = (ownEdge + 4 - this.orientation) % 4;
+        const neighEdge = (ownEdge + 2) % 4;
+        const neighEdgeAbs = (neighEdge + 4 - neighbor.orientation) % 4;
+        return this.sprite.matches(ownEdgeAbs, neighbor.sprite, neighEdgeAbs);
+    }
+
+    public conflicts(ownEdge: Direction, neighbor: Tile): boolean {
+        return !this.matches(ownEdge, neighbor);
+    }
+
+    public draw(context: CanvasRenderingContext2D, x: number, y: number) {
+        this.sprite.draw(context, x, y, this.orientation);
+    }
+}
+
+function pickRandom<T>(a: T[]): T {
+    return a[Math.round(Math.random() * (a.length - 1))];
+}

src/render.ts

@@ -0,0 +1,3 @@
+export interface IRender {
+    render(context: CanvasRenderingContext2D): void;
+}