manual/examples/voxel-geometry-culled-faces.html

<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <title>Three.js - Voxel Geometry - Culled Faces</title>
    <style>
    html, body {
        height: 100%;
        margin: 0;
    }
    #c {
        width: 100%;
        height: 100%;
        display: block;
    }
    </style>
  </head>
  <body>
    <canvas id="c"></canvas>
  </body>
<script type="importmap">
{
  "imports": {
    "three": "../../build/three.module.js",
    "three/addons/": "../../examples/jsm/"
  }
}
</script>

<script type="module">
import * as THREE from 'three';
import { OrbitControls } from 'three/addons/controls/OrbitControls.js';

class VoxelWorld {

	constructor( cellSize ) {

		this.cellSize = cellSize;
		this.cellSliceSize = cellSize * cellSize;
		this.cell = new Uint8Array( cellSize * cellSize * cellSize );

	}
	computeVoxelOffset( x, y, z ) {

		const { cellSize, cellSliceSize } = this;
		const voxelX = THREE.MathUtils.euclideanModulo( x, cellSize ) | 0;
		const voxelY = THREE.MathUtils.euclideanModulo( y, cellSize ) | 0;
		const voxelZ = THREE.MathUtils.euclideanModulo( z, cellSize ) | 0;
		return voxelY * cellSliceSize +
           voxelZ * cellSize +
           voxelX;

	}
	getCellForVoxel( x, y, z ) {

		const { cellSize } = this;
		const cellX = Math.floor( x / cellSize );
		const cellY = Math.floor( y / cellSize );
		const cellZ = Math.floor( z / cellSize );
		if ( cellX !== 0 || cellY !== 0 || cellZ !== 0 ) {

			return null;

		}

		return this.cell;

	}
	setVoxel( x, y, z, v ) {

		const cell = this.getCellForVoxel( x, y, z );
		if ( ! cell ) {

			return; // TODO: add a new cell?

		}

		const voxelOffset = this.computeVoxelOffset( x, y, z );
		cell[ voxelOffset ] = v;

	}
	getVoxel( x, y, z ) {

		const cell = this.getCellForVoxel( x, y, z );
		if ( ! cell ) {

			return 0;

		}

		const voxelOffset = this.computeVoxelOffset( x, y, z );
		return cell[ voxelOffset ];

	}
	generateGeometryDataForCell( cellX, cellY, cellZ ) {

		const { cellSize } = this;
		const positions = [];
		const normals = [];
		const indices = [];
		const startX = cellX * cellSize;
		const startY = cellY * cellSize;
		const startZ = cellZ * cellSize;

		for ( let y = 0; y < cellSize; ++ y ) {

			const voxelY = startY + y;
			for ( let z = 0; z < cellSize; ++ z ) {

				const voxelZ = startZ + z;
				for ( let x = 0; x < cellSize; ++ x ) {

					const voxelX = startX + x;
					const voxel = this.getVoxel( voxelX, voxelY, voxelZ );
					if ( voxel ) {

						// There is a voxel here but do we need faces for it?
						for ( const { dir, corners } of VoxelWorld.faces ) {

							const neighbor = this.getVoxel(
								voxelX + dir[ 0 ],
								voxelY + dir[ 1 ],
								voxelZ + dir[ 2 ] );
							if ( ! neighbor ) {

								// this voxel has no neighbor in this direction so we need a face.
								const ndx = positions.length / 3;
								for ( const pos of corners ) {

									positions.push( pos[ 0 ] + x, pos[ 1 ] + y, pos[ 2 ] + z );
									normals.push( ...dir );

								}

								indices.push(
									ndx, ndx + 1, ndx + 2,
									ndx + 2, ndx + 1, ndx + 3,
								);

							}

						}

					}

				}

			}

		}

		return {
			positions,
			normals,
			indices,
		};

	}

}

VoxelWorld.faces = [
	{ // left
		dir: [ - 1, 0, 0, ],
		corners: [
			[ 0, 1, 0 ],
			[ 0, 0, 0 ],
			[ 0, 1, 1 ],
			[ 0, 0, 1 ],
		],
	},
	{ // right
		dir: [ 1, 0, 0, ],
		corners: [
			[ 1, 1, 1 ],
			[ 1, 0, 1 ],
			[ 1, 1, 0 ],
			[ 1, 0, 0 ],
		],
	},
	{ // bottom
		dir: [ 0, - 1, 0, ],
		corners: [
			[ 1, 0, 1 ],
			[ 0, 0, 1 ],
			[ 1, 0, 0 ],
			[ 0, 0, 0 ],
		],
	},
	{ // top
		dir: [ 0, 1, 0, ],
		corners: [
			[ 0, 1, 1 ],
			[ 1, 1, 1 ],
			[ 0, 1, 0 ],
			[ 1, 1, 0 ],
		],
	},
	{ // back
		dir: [ 0, 0, - 1, ],
		corners: [
			[ 1, 0, 0 ],
			[ 0, 0, 0 ],
			[ 1, 1, 0 ],
			[ 0, 1, 0 ],
		],
	},
	{ // front
		dir: [ 0, 0, 1, ],
		corners: [
			[ 0, 0, 1 ],
			[ 1, 0, 1 ],
			[ 0, 1, 1 ],
			[ 1, 1, 1 ],
		],
	},
];

function main() {

	const canvas = document.querySelector( '#c' );
	const renderer = new THREE.WebGLRenderer( { antialias: true, canvas } );

	const cellSize = 32;

	const fov = 75;
	const aspect = 2; // the canvas default
	const near = 0.1;
	const far = 1000;
	const camera = new THREE.PerspectiveCamera( fov, aspect, near, far );
	camera.position.set( - cellSize * .3, cellSize * .8, - cellSize * .3 );

	const controls = new OrbitControls( camera, canvas );
	controls.target.set( cellSize / 2, cellSize / 3, cellSize / 2 );
	controls.update();

	const scene = new THREE.Scene();
	scene.background = new THREE.Color( 'lightblue' );

	function addLight( x, y, z ) {

		const color = 0xFFFFFF;
		const intensity = 3;
		const light = new THREE.DirectionalLight( color, intensity );
		light.position.set( x, y, z );
		scene.add( light );

	}

	addLight( - 1, 2, 4 );
	addLight( 1, - 1, - 2 );

	const world = new VoxelWorld( cellSize );

	for ( let y = 0; y < cellSize; ++ y ) {

		for ( let z = 0; z < cellSize; ++ z ) {

			for ( let x = 0; x < cellSize; ++ x ) {

				const height = ( Math.sin( x / cellSize * Math.PI * 2 ) + Math.sin( z / cellSize * Math.PI * 3 ) ) * ( cellSize / 6 ) + ( cellSize / 2 );
				if ( y < height ) {

					world.setVoxel( x, y, z, 1 );

				}

			}

		}

	}

	const { positions, normals, indices } = world.generateGeometryDataForCell( 0, 0, 0 );
	const geometry = new THREE.BufferGeometry();
	const material = new THREE.MeshLambertMaterial( { color: 'green' } );

	const positionNumComponents = 3;
	const normalNumComponents = 3;
	geometry.setAttribute(
		'position',
		new THREE.BufferAttribute( new Float32Array( positions ), positionNumComponents ) );
	geometry.setAttribute(
		'normal',
		new THREE.BufferAttribute( new Float32Array( normals ), normalNumComponents ) );
	geometry.setIndex( indices );
	const mesh = new THREE.Mesh( geometry, material );
	scene.add( mesh );

	function resizeRendererToDisplaySize( renderer ) {

		const canvas = renderer.domElement;
		const width = canvas.clientWidth;
		const height = canvas.clientHeight;
		const needResize = canvas.width !== width || canvas.height !== height;
		if ( needResize ) {

			renderer.setSize( width, height, false );

		}

		return needResize;

	}

	let renderRequested = false;

	function render() {

		renderRequested = undefined;

		if ( resizeRendererToDisplaySize( renderer ) ) {

			const canvas = renderer.domElement;
			camera.aspect = canvas.clientWidth / canvas.clientHeight;
			camera.updateProjectionMatrix();

		}

		controls.update();
		renderer.render( scene, camera );

	}

	render();

	function requestRenderIfNotRequested() {

		if ( ! renderRequested ) {

			renderRequested = true;
			requestAnimationFrame( render );

		}

	}

	controls.addEventListener( 'change', requestRenderIfNotRequested );
	window.addEventListener( 'resize', requestRenderIfNotRequested );

}

main();
</script>
</html>