357 lines
8.3 KiB
JavaScript
357 lines
8.3 KiB
JavaScript
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import {
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BufferGeometry,
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Float32BufferAttribute,
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Matrix4,
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Vector3
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} from 'three';
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/**
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* You can use this geometry to create a decal mesh, that serves different kinds of purposes.
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* e.g. adding unique details to models, performing dynamic visual environmental changes or covering seams.
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*
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* Constructor parameter:
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*
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* mesh — Any mesh object
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* position — Position of the decal projector
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* orientation — Orientation of the decal projector
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* size — Size of the decal projector
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*
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* reference: http://blog.wolfire.com/2009/06/how-to-project-decals/
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*
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*/
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class DecalGeometry extends BufferGeometry {
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constructor( mesh, position, orientation, size ) {
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super();
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// buffers
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const vertices = [];
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const normals = [];
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const uvs = [];
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// helpers
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const plane = new Vector3();
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// this matrix represents the transformation of the decal projector
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const projectorMatrix = new Matrix4();
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projectorMatrix.makeRotationFromEuler( orientation );
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projectorMatrix.setPosition( position );
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const projectorMatrixInverse = new Matrix4();
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projectorMatrixInverse.copy( projectorMatrix ).invert();
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// generate buffers
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generate();
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// build geometry
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this.setAttribute( 'position', new Float32BufferAttribute( vertices, 3 ) );
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this.setAttribute( 'normal', new Float32BufferAttribute( normals, 3 ) );
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this.setAttribute( 'uv', new Float32BufferAttribute( uvs, 2 ) );
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function generate() {
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let decalVertices = [];
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const vertex = new Vector3();
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const normal = new Vector3();
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// handle different geometry types
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const geometry = mesh.geometry;
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const positionAttribute = geometry.attributes.position;
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const normalAttribute = geometry.attributes.normal;
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// first, create an array of 'DecalVertex' objects
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// three consecutive 'DecalVertex' objects represent a single face
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//
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// this data structure will be later used to perform the clipping
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if ( geometry.index !== null ) {
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// indexed BufferGeometry
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const index = geometry.index;
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for ( let i = 0; i < index.count; i ++ ) {
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vertex.fromBufferAttribute( positionAttribute, index.getX( i ) );
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normal.fromBufferAttribute( normalAttribute, index.getX( i ) );
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pushDecalVertex( decalVertices, vertex, normal );
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}
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} else {
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// non-indexed BufferGeometry
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for ( let i = 0; i < positionAttribute.count; i ++ ) {
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vertex.fromBufferAttribute( positionAttribute, i );
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normal.fromBufferAttribute( normalAttribute, i );
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pushDecalVertex( decalVertices, vertex, normal );
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}
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}
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// second, clip the geometry so that it doesn't extend out from the projector
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decalVertices = clipGeometry( decalVertices, plane.set( 1, 0, 0 ) );
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decalVertices = clipGeometry( decalVertices, plane.set( - 1, 0, 0 ) );
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decalVertices = clipGeometry( decalVertices, plane.set( 0, 1, 0 ) );
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decalVertices = clipGeometry( decalVertices, plane.set( 0, - 1, 0 ) );
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decalVertices = clipGeometry( decalVertices, plane.set( 0, 0, 1 ) );
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decalVertices = clipGeometry( decalVertices, plane.set( 0, 0, - 1 ) );
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// third, generate final vertices, normals and uvs
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for ( let i = 0; i < decalVertices.length; i ++ ) {
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const decalVertex = decalVertices[ i ];
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// create texture coordinates (we are still in projector space)
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uvs.push(
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0.5 + ( decalVertex.position.x / size.x ),
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0.5 + ( decalVertex.position.y / size.y )
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);
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// transform the vertex back to world space
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decalVertex.position.applyMatrix4( projectorMatrix );
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// now create vertex and normal buffer data
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vertices.push( decalVertex.position.x, decalVertex.position.y, decalVertex.position.z );
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normals.push( decalVertex.normal.x, decalVertex.normal.y, decalVertex.normal.z );
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}
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}
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function pushDecalVertex( decalVertices, vertex, normal ) {
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// transform the vertex to world space, then to projector space
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vertex.applyMatrix4( mesh.matrixWorld );
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vertex.applyMatrix4( projectorMatrixInverse );
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normal.transformDirection( mesh.matrixWorld );
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decalVertices.push( new DecalVertex( vertex.clone(), normal.clone() ) );
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}
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function clipGeometry( inVertices, plane ) {
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const outVertices = [];
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const s = 0.5 * Math.abs( size.dot( plane ) );
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// a single iteration clips one face,
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// which consists of three consecutive 'DecalVertex' objects
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for ( let i = 0; i < inVertices.length; i += 3 ) {
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let total = 0;
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let nV1;
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let nV2;
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let nV3;
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let nV4;
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const d1 = inVertices[ i + 0 ].position.dot( plane ) - s;
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const d2 = inVertices[ i + 1 ].position.dot( plane ) - s;
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const d3 = inVertices[ i + 2 ].position.dot( plane ) - s;
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const v1Out = d1 > 0;
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const v2Out = d2 > 0;
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const v3Out = d3 > 0;
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// calculate, how many vertices of the face lie outside of the clipping plane
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total = ( v1Out ? 1 : 0 ) + ( v2Out ? 1 : 0 ) + ( v3Out ? 1 : 0 );
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switch ( total ) {
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case 0: {
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// the entire face lies inside of the plane, no clipping needed
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outVertices.push( inVertices[ i ] );
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outVertices.push( inVertices[ i + 1 ] );
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outVertices.push( inVertices[ i + 2 ] );
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break;
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}
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case 1: {
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// one vertex lies outside of the plane, perform clipping
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if ( v1Out ) {
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nV1 = inVertices[ i + 1 ];
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nV2 = inVertices[ i + 2 ];
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nV3 = clip( inVertices[ i ], nV1, plane, s );
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nV4 = clip( inVertices[ i ], nV2, plane, s );
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}
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if ( v2Out ) {
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nV1 = inVertices[ i ];
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nV2 = inVertices[ i + 2 ];
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nV3 = clip( inVertices[ i + 1 ], nV1, plane, s );
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nV4 = clip( inVertices[ i + 1 ], nV2, plane, s );
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outVertices.push( nV3 );
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outVertices.push( nV2.clone() );
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outVertices.push( nV1.clone() );
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outVertices.push( nV2.clone() );
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outVertices.push( nV3.clone() );
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outVertices.push( nV4 );
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break;
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}
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if ( v3Out ) {
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nV1 = inVertices[ i ];
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nV2 = inVertices[ i + 1 ];
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nV3 = clip( inVertices[ i + 2 ], nV1, plane, s );
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nV4 = clip( inVertices[ i + 2 ], nV2, plane, s );
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}
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outVertices.push( nV1.clone() );
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outVertices.push( nV2.clone() );
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outVertices.push( nV3 );
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outVertices.push( nV4 );
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outVertices.push( nV3.clone() );
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outVertices.push( nV2.clone() );
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break;
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}
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case 2: {
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// two vertices lies outside of the plane, perform clipping
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if ( ! v1Out ) {
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nV1 = inVertices[ i ].clone();
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nV2 = clip( nV1, inVertices[ i + 1 ], plane, s );
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nV3 = clip( nV1, inVertices[ i + 2 ], plane, s );
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outVertices.push( nV1 );
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outVertices.push( nV2 );
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outVertices.push( nV3 );
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}
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if ( ! v2Out ) {
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nV1 = inVertices[ i + 1 ].clone();
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nV2 = clip( nV1, inVertices[ i + 2 ], plane, s );
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nV3 = clip( nV1, inVertices[ i ], plane, s );
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outVertices.push( nV1 );
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outVertices.push( nV2 );
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outVertices.push( nV3 );
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}
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if ( ! v3Out ) {
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nV1 = inVertices[ i + 2 ].clone();
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nV2 = clip( nV1, inVertices[ i ], plane, s );
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nV3 = clip( nV1, inVertices[ i + 1 ], plane, s );
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outVertices.push( nV1 );
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outVertices.push( nV2 );
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outVertices.push( nV3 );
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}
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break;
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}
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case 3: {
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// the entire face lies outside of the plane, so let's discard the corresponding vertices
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break;
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}
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}
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}
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return outVertices;
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}
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function clip( v0, v1, p, s ) {
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const d0 = v0.position.dot( p ) - s;
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const d1 = v1.position.dot( p ) - s;
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const s0 = d0 / ( d0 - d1 );
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const v = new DecalVertex(
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new Vector3(
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v0.position.x + s0 * ( v1.position.x - v0.position.x ),
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v0.position.y + s0 * ( v1.position.y - v0.position.y ),
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v0.position.z + s0 * ( v1.position.z - v0.position.z )
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),
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new Vector3(
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v0.normal.x + s0 * ( v1.normal.x - v0.normal.x ),
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v0.normal.y + s0 * ( v1.normal.y - v0.normal.y ),
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v0.normal.z + s0 * ( v1.normal.z - v0.normal.z )
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)
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);
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// need to clip more values (texture coordinates)? do it this way:
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// intersectpoint.value = a.value + s * ( b.value - a.value );
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return v;
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}
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}
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}
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// helper
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class DecalVertex {
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constructor( position, normal ) {
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this.position = position;
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this.normal = normal;
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}
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clone() {
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return new this.constructor( this.position.clone(), this.normal.clone() );
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}
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}
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export { DecalGeometry, DecalVertex };
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