three.js/examples/js/modifiers/TessellateModifier.js

( function () {

	/**
 * Break faces with edges longer than maxEdgeLength
 */

	class TessellateModifier {

		constructor( maxEdgeLength = 0.1, maxIterations = 6 ) {

			this.maxEdgeLength = maxEdgeLength;
			this.maxIterations = maxIterations;

		}

		modify( geometry ) {

			if ( geometry.index !== null ) {

				geometry = geometry.toNonIndexed();

			} //


			const maxIterations = this.maxIterations;
			const maxEdgeLengthSquared = this.maxEdgeLength * this.maxEdgeLength;
			const va = new THREE.Vector3();
			const vb = new THREE.Vector3();
			const vc = new THREE.Vector3();
			const vm = new THREE.Vector3();
			const vs = [ va, vb, vc, vm ];
			const na = new THREE.Vector3();
			const nb = new THREE.Vector3();
			const nc = new THREE.Vector3();
			const nm = new THREE.Vector3();
			const ns = [ na, nb, nc, nm ];
			const ca = new THREE.Color();
			const cb = new THREE.Color();
			const cc = new THREE.Color();
			const cm = new THREE.Color();
			const cs = [ ca, cb, cc, cm ];
			const ua = new THREE.Vector2();
			const ub = new THREE.Vector2();
			const uc = new THREE.Vector2();
			const um = new THREE.Vector2();
			const us = [ ua, ub, uc, um ];
			const u2a = new THREE.Vector2();
			const u2b = new THREE.Vector2();
			const u2c = new THREE.Vector2();
			const u2m = new THREE.Vector2();
			const u2s = [ u2a, u2b, u2c, u2m ];
			const attributes = geometry.attributes;
			const hasNormals = attributes.normal !== undefined;
			const hasColors = attributes.color !== undefined;
			const hasUVs = attributes.uv !== undefined;
			const hasUV2s = attributes.uv2 !== undefined;
			let positions = attributes.position.array;
			let normals = hasNormals ? attributes.normal.array : null;
			let colors = hasColors ? attributes.color.array : null;
			let uvs = hasUVs ? attributes.uv.array : null;
			let uv2s = hasUV2s ? attributes.uv2.array : null;
			let positions2 = positions;
			let normals2 = normals;
			let colors2 = colors;
			let uvs2 = uvs;
			let uv2s2 = uv2s;
			let iteration = 0;
			let tessellating = true;

			function addTriangle( a, b, c ) {

				const v1 = vs[ a ];
				const v2 = vs[ b ];
				const v3 = vs[ c ];
				positions2.push( v1.x, v1.y, v1.z );
				positions2.push( v2.x, v2.y, v2.z );
				positions2.push( v3.x, v3.y, v3.z );

				if ( hasNormals ) {

					const n1 = ns[ a ];
					const n2 = ns[ b ];
					const n3 = ns[ c ];
					normals2.push( n1.x, n1.y, n1.z );
					normals2.push( n2.x, n2.y, n2.z );
					normals2.push( n3.x, n3.y, n3.z );

				}

				if ( hasColors ) {

					const c1 = cs[ a ];
					const c2 = cs[ b ];
					const c3 = cs[ c ];
					colors2.push( c1.x, c1.y, c1.z );
					colors2.push( c2.x, c2.y, c2.z );
					colors2.push( c3.x, c3.y, c3.z );

				}

				if ( hasUVs ) {

					const u1 = us[ a ];
					const u2 = us[ b ];
					const u3 = us[ c ];
					uvs2.push( u1.x, u1.y );
					uvs2.push( u2.x, u2.y );
					uvs2.push( u3.x, u3.y );

				}

				if ( hasUV2s ) {

					const u21 = u2s[ a ];
					const u22 = u2s[ b ];
					const u23 = u2s[ c ];
					uv2s2.push( u21.x, u21.y );
					uv2s2.push( u22.x, u22.y );
					uv2s2.push( u23.x, u23.y );

				}

			}

			while ( tessellating && iteration < maxIterations ) {

				iteration ++;
				tessellating = false;
				positions = positions2;
				positions2 = [];

				if ( hasNormals ) {

					normals = normals2;
					normals2 = [];

				}

				if ( hasColors ) {

					colors = colors2;
					colors2 = [];

				}

				if ( hasUVs ) {

					uvs = uvs2;
					uvs2 = [];

				}

				if ( hasUV2s ) {

					uv2s = uv2s2;
					uv2s2 = [];

				}

				for ( let i = 0, i2 = 0, il = positions.length; i < il; i += 9, i2 += 6 ) {

					va.fromArray( positions, i + 0 );
					vb.fromArray( positions, i + 3 );
					vc.fromArray( positions, i + 6 );

					if ( hasNormals ) {

						na.fromArray( normals, i + 0 );
						nb.fromArray( normals, i + 3 );
						nc.fromArray( normals, i + 6 );

					}

					if ( hasColors ) {

						ca.fromArray( colors, i + 0 );
						cb.fromArray( colors, i + 3 );
						cc.fromArray( colors, i + 6 );

					}

					if ( hasUVs ) {

						ua.fromArray( uvs, i2 + 0 );
						ub.fromArray( uvs, i2 + 2 );
						uc.fromArray( uvs, i2 + 4 );

					}

					if ( hasUV2s ) {

						u2a.fromArray( uv2s, i2 + 0 );
						u2b.fromArray( uv2s, i2 + 2 );
						u2c.fromArray( uv2s, i2 + 4 );

					}

					const dab = va.distanceToSquared( vb );
					const dbc = vb.distanceToSquared( vc );
					const dac = va.distanceToSquared( vc );

					if ( dab > maxEdgeLengthSquared || dbc > maxEdgeLengthSquared || dac > maxEdgeLengthSquared ) {

						tessellating = true;

						if ( dab >= dbc && dab >= dac ) {

							vm.lerpVectors( va, vb, 0.5 );
							if ( hasNormals ) nm.lerpVectors( na, nb, 0.5 );
							if ( hasColors ) cm.lerpColors( ca, cb, 0.5 );
							if ( hasUVs ) um.lerpVectors( ua, ub, 0.5 );
							if ( hasUV2s ) u2m.lerpVectors( u2a, u2b, 0.5 );
							addTriangle( 0, 3, 2 );
							addTriangle( 3, 1, 2 );

						} else if ( dbc >= dab && dbc >= dac ) {

							vm.lerpVectors( vb, vc, 0.5 );
							if ( hasNormals ) nm.lerpVectors( nb, nc, 0.5 );
							if ( hasColors ) cm.lerpColors( cb, cc, 0.5 );
							if ( hasUVs ) um.lerpVectors( ub, uc, 0.5 );
							if ( hasUV2s ) u2m.lerpVectors( u2b, u2c, 0.5 );
							addTriangle( 0, 1, 3 );
							addTriangle( 3, 2, 0 );

						} else {

							vm.lerpVectors( va, vc, 0.5 );
							if ( hasNormals ) nm.lerpVectors( na, nc, 0.5 );
							if ( hasColors ) cm.lerpColors( ca, cc, 0.5 );
							if ( hasUVs ) um.lerpVectors( ua, uc, 0.5 );
							if ( hasUV2s ) u2m.lerpVectors( u2a, u2c, 0.5 );
							addTriangle( 0, 1, 3 );
							addTriangle( 3, 1, 2 );

						}

					} else {

						addTriangle( 0, 1, 2 );

					}

				}

			}

			const geometry2 = new THREE.BufferGeometry();
			geometry2.setAttribute( 'position', new THREE.Float32BufferAttribute( positions2, 3 ) );

			if ( hasNormals ) {

				geometry2.setAttribute( 'normal', new THREE.Float32BufferAttribute( normals2, 3 ) );

			}

			if ( hasColors ) {

				geometry2.setAttribute( 'color', new THREE.Float32BufferAttribute( colors2, 3 ) );

			}

			if ( hasUVs ) {

				geometry2.setAttribute( 'uv', new THREE.Float32BufferAttribute( uvs2, 2 ) );

			}

			if ( hasUV2s ) {

				geometry2.setAttribute( 'uv2', new THREE.Float32BufferAttribute( uv2s2, 2 ) );

			}

			return geometry2;

		}

	}

	THREE.TessellateModifier = TessellateModifier;

} )();