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+/**
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+ * @author Mugen87 / https://github.com/Mugen87
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+ * @author spite / https://github.com/spite
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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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+ * 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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+
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+( function() {
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+
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+ function DecalGeometry( mesh, position, orientation, size ) {
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+
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+ THREE.BufferGeometry.call( this );
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+
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+ this.type = 'DecalGeometry';
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+
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+ // buffers
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+
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+ var vertices = [];
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+ var normals = [];
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+ var uvs = [];
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+
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+ // helpers
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+
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+ var plane = new THREE.Vector3();
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+
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+ // this matrix represents the transformation of the decal projector
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+
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+ var projectorMatrix = new THREE.Matrix4();
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+ projectorMatrix.makeRotationFromEuler( orientation );
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+ projectorMatrix.setPosition( position );
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+
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+ var projectorMatrixInverse = new THREE.Matrix4().getInverse( projectorMatrix );
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+
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+ // generate buffers
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+
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+ generate();
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+
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+ // build geometry
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+
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+ this.addAttribute( 'position', new THREE.Float32BufferAttribute( vertices, 3 ) );
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+ this.addAttribute( 'normal', new THREE.Float32BufferAttribute( normals, 3 ) );
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+ this.addAttribute( 'uv', new THREE.Float32BufferAttribute( uvs, 2 ) );
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+
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+ function generate() {
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+
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+ var i, j;
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+ var geometry = new THREE.BufferGeometry();
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+ var decalVertices = [];
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+
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+ var vertex = new THREE.Vector3();
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+ var normal = new THREE.Vector3();
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+
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+ // handle different geometry types
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+
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+ if ( mesh.geometry.isGeometry ) {
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+
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+ geometry.fromGeometry( mesh.geometry );
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+
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+ } else {
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+
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+ geometry.copy( mesh.geometry );
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+
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+ }
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+
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+ var positionAttribute = geometry.attributes.position;
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+ var normalAttribute = geometry.attributes.normal;
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+
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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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+
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+ if ( geometry.index !== null ) {
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+
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+ // indexed BufferGeometry
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+
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+ var index = geometry.index;
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+
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+ for ( i = 0; i < index.count; i ++ ) {
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+
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+ vertex.fromBufferAttribute( positionAttribute, index.getX( i ) );
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+ normal.fromBufferAttribute( normalAttribute, index.getX( i ) );
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+
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+ pushDecalVertex( decalVertices, vertex, normal );
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+
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+ }
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+
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+ } else {
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+
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+ // non-indexed BufferGeometry
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+
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+ for ( i = 0; i < positionAttribute.count; i ++ ) {
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+
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+ vertex.fromBufferAttribute( positionAttribute, i );
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+ normal.fromBufferAttribute( normalAttribute, i );
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+
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+ pushDecalVertex( decalVertices, vertex, normal );
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+
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+ }
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+
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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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+
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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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+
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+ // third, generate final vertices, normals and uvs
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+
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+ for ( i = 0; i < decalVertices.length; i ++ ) {
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+
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+ var decalVertex = decalVertices[ i ];
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+
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+ // create texture coordinates (we are still in projector space)
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+
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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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+
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+ // transform the vertex back to world space
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+
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+ decalVertex.position.applyMatrix4( projectorMatrix );
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+
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+ // now create vertex and normal buffer data
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+
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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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+
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+ }
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+
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+ function pushDecalVertex( decalVertices, vertex, normal ) {
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+
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+ // transform the vertex to world space, then to projector space
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+
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+ vertex.applyMatrix4( mesh.matrix );
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+ vertex.applyMatrix4( projectorMatrixInverse );
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+
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+ decalVertices.push( new DecalVertex( vertex.clone(), normal.clone() ) );
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+
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+ }
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+
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+ function clipGeometry( inVertices, plane ) {
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+
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+ var outVertices = [];
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+
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+ var s = 0.5 * Math.abs( size.dot( plane ) );
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+
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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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+
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+ for ( var i = 0; i < inVertices.length; i += 3 ) {
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+
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+ var v1Out, v2Out, v3Out, total = 0;
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+ var nV1, nV2, nV3, nV4;
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+
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+ var d1 = inVertices[ i + 0 ].position.dot( plane ) - s;
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+ var d2 = inVertices[ i + 1 ].position.dot( plane ) - s;
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+ var d3 = inVertices[ i + 2 ].position.dot( plane ) - s;
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+
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+ v1Out = d1 > 0;
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+ v2Out = d2 > 0;
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+ v3Out = d3 > 0;
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+
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+ // calculate, how many vertices of the face lie outside of the clipping plane
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+
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+ total = ( v1Out ? 1 : 0 ) + ( v2Out ? 1 : 0 ) + ( v3Out ? 1 : 0 );
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+
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+ switch ( total ) {
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+
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+ case 0: {
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+
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+ // the entire face lies inside of the plane, no clipping needed
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+
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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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+ }
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+
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+ case 1: {
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+
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+ // one vertex lies outside of the plane, perform clipping
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+
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+ if ( v1Out ) {
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+
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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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+ }
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+
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+ if ( v2Out ) {
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+
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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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+
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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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+
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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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+ }
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+
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+ if ( v3Out ) {
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+
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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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+ }
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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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+
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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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+
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+ break;
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+
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+ }
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+
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+ case 2: {
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+
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+ // two vertices lies outside of the plane, perform clipping
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+
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+ if ( ! v1Out ) {
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+
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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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+ }
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+
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+ if ( ! v2Out ) {
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+
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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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+ }
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+
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+ if ( ! v3Out ) {
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+
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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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+ }
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+
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+ break;
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+
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+ }
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+
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+ case 3: {
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+
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+ // the entire face lies outside of the plane, so let's discard the corresponding vertices
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+
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+ break;
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+
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+ }
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+
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+ }
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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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+ }
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+
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+ function clip( v0, v1, p, s ) {
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+
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+ var d0 = v0.position.dot( p ) - s;
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+ var d1 = v1.position.dot( p ) - s;
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+
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+ var s0 = d0 / ( d0 - d1 );
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+
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+ var v = new DecalVertex(
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+ new THREE.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 THREE.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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+
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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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+
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+ return v;
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+
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+ }
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+
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+ }
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+
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+ DecalGeometry.prototype = Object.create( THREE.BufferGeometry.prototype );
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+ DecalGeometry.prototype.constructor = DecalGeometry;
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+
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+ // helper
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+
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+ function DecalVertex( position, normal ) {
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+
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+ this.position = position;
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+ this.normal = normal;
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+
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+ }
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+
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+ DecalVertex.prototype.clone = function() {
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+
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+ return new DecalVertex( this.position.clone(), this.normal.clone() );
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+
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+ };
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+
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+ // export
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+
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+ THREE.DecalGeometry = DecalGeometry;
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+
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+} ) ();
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Mugen87