three.js/src/geometries/EdgesGeometry.js

import { BufferGeometry } from '../core/BufferGeometry.js';
import { Float32BufferAttribute } from '../core/BufferAttribute.js';
import * as MathUtils from '../math/MathUtils.js';
import { Triangle } from '../math/Triangle.js';
import { Vector3 } from '../math/Vector3.js';

const _v0 = /*@__PURE__*/ new Vector3();
const _v1 = /*@__PURE__*/ new Vector3();
const _normal = /*@__PURE__*/ new Vector3();
const _triangle = /*@__PURE__*/ new Triangle();

class EdgesGeometry extends BufferGeometry {

	constructor( geometry = null, thresholdAngle = 1 ) {

		super();

		this.type = 'EdgesGeometry';

		this.parameters = {
			geometry: geometry,
			thresholdAngle: thresholdAngle
		};

		if ( geometry !== null ) {

			const precisionPoints = 4;
			const precision = Math.pow( 10, precisionPoints );
			const thresholdDot = Math.cos( MathUtils.DEG2RAD * thresholdAngle );

			const indexAttr = geometry.getIndex();
			const positionAttr = geometry.getAttribute( 'position' );
			const indexCount = indexAttr ? indexAttr.count : positionAttr.count;

			const indexArr = [ 0, 0, 0 ];
			const vertKeys = [ 'a', 'b', 'c' ];
			const hashes = new Array( 3 );

			const edgeData = {};
			const vertices = [];
			for ( let i = 0; i < indexCount; i += 3 ) {

				if ( indexAttr ) {

					indexArr[ 0 ] = indexAttr.getX( i );
					indexArr[ 1 ] = indexAttr.getX( i + 1 );
					indexArr[ 2 ] = indexAttr.getX( i + 2 );

				} else {

					indexArr[ 0 ] = i;
					indexArr[ 1 ] = i + 1;
					indexArr[ 2 ] = i + 2;

				}

				const { a, b, c } = _triangle;
				a.fromBufferAttribute( positionAttr, indexArr[ 0 ] );
				b.fromBufferAttribute( positionAttr, indexArr[ 1 ] );
				c.fromBufferAttribute( positionAttr, indexArr[ 2 ] );
				_triangle.getNormal( _normal );

				// create hashes for the edge from the vertices
				hashes[ 0 ] = `${ Math.round( a.x * precision ) },${ Math.round( a.y * precision ) },${ Math.round( a.z * precision ) }`;
				hashes[ 1 ] = `${ Math.round( b.x * precision ) },${ Math.round( b.y * precision ) },${ Math.round( b.z * precision ) }`;
				hashes[ 2 ] = `${ Math.round( c.x * precision ) },${ Math.round( c.y * precision ) },${ Math.round( c.z * precision ) }`;

				// skip degenerate triangles
				if ( hashes[ 0 ] === hashes[ 1 ] || hashes[ 1 ] === hashes[ 2 ] || hashes[ 2 ] === hashes[ 0 ] ) {

					continue;

				}

				// iterate over every edge
				for ( let j = 0; j < 3; j ++ ) {

					// get the first and next vertex making up the edge
					const jNext = ( j + 1 ) % 3;
					const vecHash0 = hashes[ j ];
					const vecHash1 = hashes[ jNext ];
					const v0 = _triangle[ vertKeys[ j ] ];
					const v1 = _triangle[ vertKeys[ jNext ] ];

					const hash = `${ vecHash0 }_${ vecHash1 }`;
					const reverseHash = `${ vecHash1 }_${ vecHash0 }`;

					if ( reverseHash in edgeData && edgeData[ reverseHash ] ) {

						// if we found a sibling edge add it into the vertex array if
						// it meets the angle threshold and delete the edge from the map.
						if ( _normal.dot( edgeData[ reverseHash ].normal ) <= thresholdDot ) {

							vertices.push( v0.x, v0.y, v0.z );
							vertices.push( v1.x, v1.y, v1.z );

						}

						edgeData[ reverseHash ] = null;

					} else if ( ! ( hash in edgeData ) ) {

						// if we've already got an edge here then skip adding a new one
						edgeData[ hash ] = {

							index0: indexArr[ j ],
							index1: indexArr[ jNext ],
							normal: _normal.clone(),

						};

					}

				}

			}

			// iterate over all remaining, unmatched edges and add them to the vertex array
			for ( const key in edgeData ) {

				if ( edgeData[ key ] ) {

					const { index0, index1 } = edgeData[ key ];
					_v0.fromBufferAttribute( positionAttr, index0 );
					_v1.fromBufferAttribute( positionAttr, index1 );

					vertices.push( _v0.x, _v0.y, _v0.z );
					vertices.push( _v1.x, _v1.y, _v1.z );

				}

			}

			this.setAttribute( 'position', new Float32BufferAttribute( vertices, 3 ) );

		}

	}

	copy( source ) {

		super.copy( source );

		this.parameters = Object.assign( {}, source.parameters );

		return this;

	}

}

export { EdgesGeometry };