three.js/examples/jsm/misc/TileCreasedNormalsPlugin.js

import { BufferAttribute } from 'three';

/**
 * A plugin for `3d-tiles-renderer` that computes creased vertex normals for the
 * geometry of each loaded tile: smooth normals everywhere except where faces meet
 * at an angle greater than the crease angle. Useful for photogrammetry tile sets
 * like Google Photorealistic 3D Tiles which come without vertex normals.
 *
 * The normals are computed in a Web Worker so tile processing doesn't block the
 * main thread. Tiles are displayed once their normals are ready.
 *
 * ```js
 * tiles.registerPlugin( new TileCreasedNormalsPlugin( { creaseAngle: Math.PI / 6 } ) );
 * ```
 *
 * @three_import import { TileCreasedNormalsPlugin } from 'three/addons/misc/TileCreasedNormalsPlugin.js';
 */
class TileCreasedNormalsPlugin {

	/**
	 * Constructs a new plugin.
	 *
	 * @param {Object} [options] - The configuration options.
	 * @param {number} [options.creaseAngle=Math.PI/3] - The crease angle in radians.
	 */
	constructor( { creaseAngle = Math.PI / 3 } = {} ) {

		/**
		 * The crease angle in radians.
		 *
		 * @type {number}
		 */
		this.creaseAngle = creaseAngle;

		this._requestId = 0;
		this._pending = new Map();

		const workerCode = `

			${ computeCreasedNormals.toString() }

			onmessage = ( { data } ) => {

				const { id, positions, creaseAngle } = data;
				const normals = computeCreasedNormals( positions, creaseAngle );
				postMessage( { id, positions, normals }, [ positions.buffer, normals.buffer ] );

			};

		`;

		this._worker = new Worker( URL.createObjectURL( new Blob( [ workerCode ] ) ) );
		this._worker.onmessage = ( { data } ) => {

			this._pending.get( data.id )( data );
			this._pending.delete( data.id );

		};

	}

	/**
	 * Called by the tiles renderer for each loaded tile model. The tile is
	 * displayed once the returned promise resolves.
	 *
	 * @param {Object3D} scene - The tile model.
	 * @return {Promise} A promise that resolves when all geometries have creased normals.
	 */
	processTileModel( scene ) {

		const promises = [];

		scene.traverse( ( mesh ) => {

			if ( mesh.geometry ) {

				promises.push( this._processMesh( mesh ) );

			}

		} );

		return Promise.all( promises );

	}

	_processMesh( mesh ) {

		const geometry = mesh.geometry.index ? mesh.geometry.toNonIndexed() : mesh.geometry;
		const positions = geometry.attributes.position.array;

		const id = this._requestId ++;
		this._worker.postMessage( { id, positions, creaseAngle: this.creaseAngle }, [ positions.buffer ] );

		return new Promise( ( resolve ) => {

			this._pending.set( id, ( { positions, normals } ) => {

				geometry.setAttribute( 'position', new BufferAttribute( positions, 3 ) );
				geometry.setAttribute( 'normal', new BufferAttribute( normals, 3 ) );
				mesh.geometry = geometry;
				resolve();

			} );

		} );

	}

	/**
	 * Called by the tiles renderer when the plugin is unregistered or the
	 * tiles renderer is disposed.
	 */
	dispose() {

		this._worker.terminate();

	}

}

// Computes creased normals for non-indexed triangle positions. The function is
// self-contained so it can be serialized into the worker.
function computeCreasedNormals( positions, creaseAngle ) {

	const creaseDot = Math.cos( creaseAngle );
	const hashMultiplier = ( 1 + 1e-10 ) * 1e2;

	const vertexCount = positions.length / 3;
	const faceCount = vertexCount / 3;

	// compute the normal of each face
	const faceNormals = new Float64Array( faceCount * 3 );
	for ( let f = 0; f < faceCount; f ++ ) {

		const f9 = 9 * f;
		const ax = positions[ f9 + 0 ], ay = positions[ f9 + 1 ], az = positions[ f9 + 2 ];
		const bx = positions[ f9 + 3 ], by = positions[ f9 + 4 ], bz = positions[ f9 + 5 ];
		const cx = positions[ f9 + 6 ], cy = positions[ f9 + 7 ], cz = positions[ f9 + 8 ];

		const v1x = cx - bx, v1y = cy - by, v1z = cz - bz;
		const v2x = ax - bx, v2y = ay - by, v2z = az - bz;

		const nx = v1y * v2z - v1z * v2y;
		const ny = v1z * v2x - v1x * v2z;
		const nz = v1x * v2y - v1y * v2x;

		const invLength = 1 / ( Math.sqrt( nx * nx + ny * ny + nz * nz ) || 1 );
		faceNormals[ 3 * f + 0 ] = nx * invLength;
		faceNormals[ 3 * f + 1 ] = ny * invLength;
		faceNormals[ 3 * f + 2 ] = nz * invLength;

	}

	// assign an id to each vertex, sharing the id between vertices with the same
	// quantized position via an open-addressed hash table (slots hold id + 1, 0 means empty)
	const vertexIds = new Int32Array( vertexCount );
	const quantized = new Int32Array( vertexCount * 3 );

	let tableSize = 1;
	while ( tableSize < vertexCount * 2 ) tableSize <<= 1;
	const tableMask = tableSize - 1;
	const table = new Int32Array( tableSize );

	let uniqueCount = 0;
	for ( let i = 0; i < vertexCount; i ++ ) {

		const i3 = 3 * i;
		const qx = ~ ~ ( positions[ i3 + 0 ] * hashMultiplier );
		const qy = ~ ~ ( positions[ i3 + 1 ] * hashMultiplier );
		const qz = ~ ~ ( positions[ i3 + 2 ] * hashMultiplier );

		let slot = ( Math.imul( qx, 73856093 ) ^ Math.imul( qy, 19349663 ) ^ Math.imul( qz, 83492791 ) ) & tableMask;

		while ( true ) {

			const id = table[ slot ];

			if ( id === 0 ) {

				const q3 = 3 * uniqueCount;
				quantized[ q3 + 0 ] = qx;
				quantized[ q3 + 1 ] = qy;
				quantized[ q3 + 2 ] = qz;

				table[ slot ] = uniqueCount + 1;
				vertexIds[ i ] = uniqueCount ++;
				break;

			}

			const q3 = 3 * ( id - 1 );

			if ( quantized[ q3 + 0 ] === qx && quantized[ q3 + 1 ] === qy && quantized[ q3 + 2 ] === qz ) {

				vertexIds[ i ] = id - 1;
				break;

			}

			slot = ( slot + 1 ) & tableMask;

		}

	}

	// bucket the faces surrounding each unique vertex position
	const bucketOffsets = new Int32Array( uniqueCount + 1 );
	for ( let i = 0; i < vertexCount; i ++ ) bucketOffsets[ vertexIds[ i ] + 1 ] ++;
	for ( let i = 0; i < uniqueCount; i ++ ) bucketOffsets[ i + 1 ] += bucketOffsets[ i ];

	const bucketFaces = new Int32Array( vertexCount );
	const bucketCursors = bucketOffsets.slice( 0, uniqueCount );
	for ( let f = 0; f < faceCount; f ++ ) {

		const f3 = 3 * f;
		bucketFaces[ bucketCursors[ vertexIds[ f3 + 0 ] ] ++ ] = f;
		bucketFaces[ bucketCursors[ vertexIds[ f3 + 1 ] ] ++ ] = f;
		bucketFaces[ bucketCursors[ vertexIds[ f3 + 2 ] ] ++ ] = f;

	}

	// average the normals of the faces surrounding each vertex if they are within the
	// provided crease threshold
	const normalArray = new Float32Array( vertexCount * 3 );
	for ( let f = 0; f < faceCount; f ++ ) {

		const f3 = 3 * f;
		const nx = faceNormals[ f3 + 0 ];
		const ny = faceNormals[ f3 + 1 ];
		const nz = faceNormals[ f3 + 2 ];

		for ( let n = 0; n < 3; n ++ ) {

			const i = f3 + n;
			const id = vertexIds[ i ];

			let sumX = 0, sumY = 0, sumZ = 0;

			for ( let k = bucketOffsets[ id ], end = bucketOffsets[ id + 1 ]; k < end; k ++ ) {

				const o3 = 3 * bucketFaces[ k ];
				const ox = faceNormals[ o3 + 0 ];
				const oy = faceNormals[ o3 + 1 ];
				const oz = faceNormals[ o3 + 2 ];

				if ( nx * ox + ny * oy + nz * oz > creaseDot ) {

					sumX += ox;
					sumY += oy;
					sumZ += oz;

				}

			}

			const invLength = 1 / ( Math.sqrt( sumX * sumX + sumY * sumY + sumZ * sumZ ) || 1 );
			normalArray[ 3 * i + 0 ] = sumX * invLength;
			normalArray[ 3 * i + 1 ] = sumY * invLength;
			normalArray[ 3 * i + 2 ] = sumZ * invLength;

		}

	}

	return normalArray;

}

export { TileCreasedNormalsPlugin };