Caves!!

world.js

@@ -1,7 +1,7 @@
 import { makeBufferFromFaces, makeFace } from "./geometry";
 import { loadTexture, makeProgram } from "./gl";
 import * as se3 from './se3';
-import { makeTerrain, random } from "./terrain";
+import { checkCave, makeTerrain, random } from "./terrain";
 
 const VSHADER = `
 attribute vec3 aPosition;
@@ -132,6 +132,54 @@ function makeChunk(z, x) {
         makeATree(data, tree, seed, z, x);
     }
 
+    // caves
+    // [ ] 3d perlin noise up to 64
+    // [ ] sample 4x4x4 to check for caves
+    // [ ] fill with air where appropriate
+
+    function propagateCave(i, j, k) {
+        const neighbors = (i, j, k) => [
+            [i - 1, j, k],
+            [i + 1, j, k],
+            [i, j - 1, k],
+            [i, j + 1, k],
+            [i, j, k - 1],
+            [i, j, k + 1],
+        ];
+
+        const queue = neighbors(i, j, k);
+
+        while (queue.length > 0) {
+            const [ni, nj, nk] = queue.pop();
+            if (ni < 0 || ni > 15 || nj < 0 || nj > 15 || nk < 0 || nk > 255) {
+                continue;
+            }
+            const bi = 256 * (16 * ni + nj) + nk;
+            if (data[bi] === BlockType.AIR || data[bi] === BlockType.WATER) {
+                continue;
+            }
+            if (checkCave(seed, x + nj, nk, z + ni)) {
+                data[bi] = BlockType.AIR;
+                queue.push(...neighbors(ni, nj, nk));
+            }
+        }
+    }
+
+    for (let i = 0; i < 16; i += 4) {
+        for (let j = 0; j < 16; j += 4) {
+            let bi = 256 * (16 * i + j);
+            for (let k = 0; k < 58; k += 4, bi += 4) {
+                if (data[bi] === BlockType.AIR) {
+                    continue;
+                }
+                if (checkCave(seed, x + j, k, z + i)) {
+                    data[bi] = BlockType.AIR;
+                    propagateCave(i, j, k);
+                }
+            }
+        }
+    }
+
     return {
         position: {z, x},
         data,
@@ -302,7 +350,7 @@ function makeFaces(chunk, blocks, neighbors) {
                 .filter(({ block }) => isTransparent(block) && block !== BlockType.WATER)
             ) {
                 if (chunk.data[bi] === BlockType.WATER) {
-                    faceCenter[1] -= 0.15;
+                    faceCenter[1] -= 0.15;  // TODO: lower face should be normal
                 }
                 chunk.transparentFaces.push({
                     dir,