Function makeRecursiveCubeModel

assets/js/block_ninja.js:573–629

({ recursionLevel, splitFn, color, scale=1 })

// Not very optimized - lots of duplicate vertices are generated.
function makeRecursiveCubeModel({ recursionLevel, splitFn, color, scale=1 }) {
	const getScaleAtLevel = level => 1 / (3 ** level);

	// We can model level 0 manually. It's just a single, centered, cube.
	let cubeOrigins = [{ x: 0, y: 0, z: 0 }];

	// Recursively replace cubes with smaller cubes.
	for (let i=1; i<=recursionLevel; i++) {
		const scale = getScaleAtLevel(i) * 2;
		const cubeOrigins2 = [];
		cubeOrigins.forEach(origin => {
			cubeOrigins2.push(...splitFn(origin, scale));
		});
		cubeOrigins = cubeOrigins2;
	}

	const finalModel = { vertices: [], polys: [] };

	// Generate single cube model and scale it.
	const cubeModel = makeCubeModel({ scale: 1 });
	cubeModel.vertices.forEach(scaleVector(getScaleAtLevel(recursionLevel)));

	// Compute the max distance x, y, or z origin values will be.
	// Same result as `Math.max(...cubeOrigins.map(o => o.x))`, but much faster.
	const maxComponent = getScaleAtLevel(recursionLevel) * (3 ** recursionLevel - 1);

	// Place cube geometry at each origin.
	cubeOrigins.forEach((origin, cubeIndex) => {
		// To compute occlusion (shading), find origin component with greatest
		// magnitude and normalize it relative to `maxComponent`.
		const occlusion = Math.max(
			Math.abs(origin.x),
			Math.abs(origin.y),
			Math.abs(origin.z)
		) / maxComponent;
		// At lower iterations, occlusion looks better lightened up a bit.
		const occlusionLighter = recursionLevel > 2
			? occlusion
			: (occlusion + 0.8) / 1.8;
		// Clone, translate vertices to origin, and apply scale
		finalModel.vertices.push(
			...cubeModel.vertices.map(v => ({
				x: (v.x + origin.x) * scale,
				y: (v.y + origin.y) * scale,
				z: (v.z + origin.z) * scale
			}))
		);
		// Clone polys, shift referenced vertex indexes, and compute color.
		finalModel.polys.push(
			...cubeModel.polys.map(poly => ({
				vIndexes: poly.vIndexes.map(add(cubeIndex * 8))
			}))
		);
	});

	return finalModel;
}