Projector.js

// @ts-nocheck
import * as THREE from 'three';

/**
 * @author mrdoob / http://mrdoob.com/
 * @author supereggbert / http://www.paulbrunt.co.uk/
 * @author julianwa / https://github.com/julianwa
 */

THREE.RenderableObject = function () {
    
        this.id = 0;
    
        this.object = null;
        this.z = 0;
        this.renderOrder = 0;
    
    };
    
    //
    
    THREE.RenderableFace = function () {
    
        this.id = 0;
    
        this.v1 = new THREE.RenderableVertex();
        this.v2 = new THREE.RenderableVertex();
        this.v3 = new THREE.RenderableVertex();
    
        this.normalModel = new THREE.Vector3();
    
        this.vertexNormalsModel = [ new THREE.Vector3(), new THREE.Vector3(), new THREE.Vector3() ];
        this.vertexNormalsLength = 0;
    
        this.color = new THREE.Color();
        this.material = null;
        this.uvs = [ new THREE.Vector2(), new THREE.Vector2(), new THREE.Vector2() ];
    
        this.z = 0;
        this.renderOrder = 0;
    
    };
    
    //
    
    THREE.RenderableVertex = function () {
    
        this.position = new THREE.Vector3();
        this.positionWorld = new THREE.Vector3();
        this.positionScreen = new THREE.Vector4();
    
        this.visible = true;
    
    };
    
    THREE.RenderableVertex.prototype.copy = function ( vertex ) {
    
        this.positionWorld.copy( vertex.positionWorld );
        this.positionScreen.copy( vertex.positionScreen );
    
    };
    
    //
    
    THREE.RenderableLine = function () {
    
        this.id = 0;
    
        this.v1 = new THREE.RenderableVertex();
        this.v2 = new THREE.RenderableVertex();
    
        this.vertexColors = [ new THREE.Color(), new THREE.Color() ];
        this.material = null;
    
        this.z = 0;
        this.renderOrder = 0;
    
    };
    
    //
    
    THREE.RenderableSprite = function () {
    
        this.id = 0;
    
        this.object = null;
    
        this.x = 0;
        this.y = 0;
        this.z = 0;
    
        this.rotation = 0;
        this.scale = new THREE.Vector2();
    
        this.material = null;
        this.renderOrder = 0;
    
    };
    
    //
    
    THREE.Projector = function () {
    
        var _object, _objectCount, _objectPool = [], _objectPoolLength = 0,
            _vertex, _vertexCount, _vertexPool = [], _vertexPoolLength = 0,
            _face, _faceCount, _facePool = [], _facePoolLength = 0,
            _line, _lineCount, _linePool = [], _linePoolLength = 0,
            _sprite, _spriteCount, _spritePool = [], _spritePoolLength = 0,
    
            _renderData = { objects: [], lights: [], elements: [] },
    
            _vector3 = new THREE.Vector3(),
            _vector4 = new THREE.Vector4(),
    
            _clipBox = new THREE.Box3( new THREE.Vector3( - 1, - 1, - 1 ), new THREE.Vector3( 1, 1, 1 ) ),
            _boundingBox = new THREE.Box3(),
            _points3 = new Array( 3 ),
    
            _viewMatrix = new THREE.Matrix4(),
            _viewProjectionMatrix = new THREE.Matrix4(),
    
            _modelMatrix,
            _modelViewProjectionMatrix = new THREE.Matrix4(),
    
            _normalMatrix = new THREE.Matrix3(),
    
            _frustum = new THREE.Frustum(),
    
            _clippedVertex1PositionScreen = new THREE.Vector4(),
            _clippedVertex2PositionScreen = new THREE.Vector4();
    
        //
    
        this.projectVector = function ( vector, camera ) {
    
            console.warn( 'THREE.Projector: .projectVector() is now vector.project().' );
            vector.project( camera );
    
        };
    
        this.unprojectVector = function ( vector, camera ) {
    
            console.warn( 'THREE.Projector: .unprojectVector() is now vector.unproject().' );
            vector.unproject( camera );
    
        };
    
        this.pickingRay = function () {
    
            console.error( 'THREE.Projector: .pickingRay() is now raycaster.setFromCamera().' );
    
        };
    
        //
    
        var RenderList = function () {
    
            var normals = [];
            var colors = [];
            var uvs = [];
    
            var object = null;
            var material = null;
    
            var normalMatrix = new THREE.Matrix3();
    
            function setObject( value ) {
    
                object = value;
                material = object.material;
    
                normalMatrix.getNormalMatrix( object.matrixWorld );
    
                normals.length = 0;
                colors.length = 0;
                uvs.length = 0;
    
            }
    
            function projectVertex( vertex ) {
    
                var position = vertex.position;
                var positionWorld = vertex.positionWorld;
                var positionScreen = vertex.positionScreen;
    
                positionWorld.copy( position ).applyMatrix4( _modelMatrix );
                positionScreen.copy( positionWorld ).applyMatrix4( _viewProjectionMatrix );
    
                var invW = 1 / positionScreen.w;
    
                positionScreen.x *= invW;
                positionScreen.y *= invW;
                positionScreen.z *= invW;
    
                vertex.visible = positionScreen.x >= - 1 && positionScreen.x <= 1 &&
                         positionScreen.y >= - 1 && positionScreen.y <= 1 &&
                         positionScreen.z >= - 1 && positionScreen.z <= 1;
    
            }
    
            function pushVertex( x, y, z ) {
    
                _vertex = getNextVertexInPool();
                _vertex.position.set( x, y, z );
    
                projectVertex( _vertex );
    
            }
    
            function pushNormal( x, y, z ) {
    
                normals.push( x, y, z );
    
            }
    
            function pushColor( r, g, b ) {
    
                colors.push( r, g, b );
    
            }
    
            function pushUv( x, y ) {
    
                uvs.push( x, y );
    
            }
    
            function checkTriangleVisibility( v1, v2, v3 ) {
    
                if ( v1.visible === true || v2.visible === true || v3.visible === true ) return true;
    
                _points3[ 0 ] = v1.positionScreen;
                _points3[ 1 ] = v2.positionScreen;
                _points3[ 2 ] = v3.positionScreen;
    
                return _clipBox.intersectsBox( _boundingBox.setFromPoints( _points3 ) );
    
            }
    
            function checkBackfaceCulling( v1, v2, v3 ) {
    
                return ( ( v3.positionScreen.x - v1.positionScreen.x ) *
                        ( v2.positionScreen.y - v1.positionScreen.y ) -
                        ( v3.positionScreen.y - v1.positionScreen.y ) *
                        ( v2.positionScreen.x - v1.positionScreen.x ) ) < 0;
    
            }
    
            function pushLine( a, b ) {
    
                var v1 = _vertexPool[ a ];
                var v2 = _vertexPool[ b ];
    
                // Clip
    
                v1.positionScreen.copy( v1.position ).applyMatrix4( _modelViewProjectionMatrix );
                v2.positionScreen.copy( v2.position ).applyMatrix4( _modelViewProjectionMatrix );
    
                if ( clipLine( v1.positionScreen, v2.positionScreen ) === true ) {
    
                    // Perform the perspective divide
                    v1.positionScreen.multiplyScalar( 1 / v1.positionScreen.w );
                    v2.positionScreen.multiplyScalar( 1 / v2.positionScreen.w );
    
                    _line = getNextLineInPool();
                    _line.id = object.id;
                    _line.v1.copy( v1 );
                    _line.v2.copy( v2 );
                    _line.z = Math.max( v1.positionScreen.z, v2.positionScreen.z );
                    _line.renderOrder = object.renderOrder;
    
                    _line.material = object.material;
    
                    if ( object.material.vertexColors === THREE.VertexColors ) {
    
                        _line.vertexColors[ 0 ].fromArray( colors, a * 3 );
                        _line.vertexColors[ 1 ].fromArray( colors, b * 3 );
    
                    }
    
                    _renderData.elements.push( _line );
    
                }
    
            }
    
            function pushTriangle( a, b, c ) {
    
                var v1 = _vertexPool[ a ];
                var v2 = _vertexPool[ b ];
                var v3 = _vertexPool[ c ];
    
                if ( checkTriangleVisibility( v1, v2, v3 ) === false ) return;
    
                if ( material.side === THREE.DoubleSide || checkBackfaceCulling( v1, v2, v3 ) === true ) {
    
                    _face = getNextFaceInPool();
    
                    _face.id = object.id;
                    _face.v1.copy( v1 );
                    _face.v2.copy( v2 );
                    _face.v3.copy( v3 );
                    _face.z = ( v1.positionScreen.z + v2.positionScreen.z + v3.positionScreen.z ) / 3;
                    _face.renderOrder = object.renderOrder;
    
                    // use first vertex normal as face normal
    
                    _face.normalModel.fromArray( normals, a * 3 );
                    _face.normalModel.applyMatrix3( normalMatrix ).normalize();
    
                    for ( var i = 0; i < 3; i ++ ) {
    
                        var normal = _face.vertexNormalsModel[ i ];
                        normal.fromArray( normals, arguments[ i ] * 3 );
                        normal.applyMatrix3( normalMatrix ).normalize();
    
                        var uv = _face.uvs[ i ];
                        uv.fromArray( uvs, arguments[ i ] * 2 );
    
                    }
    
                    _face.vertexNormalsLength = 3;
    
                    _face.material = object.material;
    
                    _renderData.elements.push( _face );
    
                }
    
            }
    
            return {
                setObject: setObject,
                projectVertex: projectVertex,
                checkTriangleVisibility: checkTriangleVisibility,
                checkBackfaceCulling: checkBackfaceCulling,
                pushVertex: pushVertex,
                pushNormal: pushNormal,
                pushColor: pushColor,
                pushUv: pushUv,
                pushLine: pushLine,
                pushTriangle: pushTriangle
            };
    
        };
    
        var renderList = new RenderList();
    
        function projectObject( object ) {
    
            if ( object.visible === false ) return;
    
            if ( object instanceof THREE.Light ) {
    
                _renderData.lights.push( object );
    
            } else if ( object instanceof THREE.Mesh || object instanceof THREE.Line || object instanceof THREE.Points ) {
    
                if ( object.material.visible === false ) return;
                if ( object.frustumCulled === true && _frustum.intersectsObject( object ) === false ) return;
    
                addObject( object );
    
            } else if ( object instanceof THREE.Sprite ) {
    
                if ( object.material.visible === false ) return;
                if ( object.frustumCulled === true && _frustum.intersectsSprite( object ) === false ) return;
    
                addObject( object );
    
            }
    
            var children = object.children;
    
            for ( var i = 0, l = children.length; i < l; i ++ ) {
    
                projectObject( children[ i ] );
    
            }
    
        }
    
        function addObject( object ) {
    
            _object = getNextObjectInPool();
            _object.id = object.id;
            _object.object = object;
    
            _vector3.setFromMatrixPosition( object.matrixWorld );
            _vector3.applyMatrix4( _viewProjectionMatrix );
            _object.z = _vector3.z;
            _object.renderOrder = object.renderOrder;
    
            _renderData.objects.push( _object );
    
        }
    
        this.projectScene = function ( scene, camera, sortObjects, sortElements ) {
    
            _faceCount = 0;
            _lineCount = 0;
            _spriteCount = 0;
    
            _renderData.elements.length = 0;
    
            if ( scene.autoUpdate === true ) scene.updateMatrixWorld();
            if ( camera.parent === null ) camera.updateMatrixWorld();
    
            _viewMatrix.copy( camera.matrixWorldInverse );
            _viewProjectionMatrix.multiplyMatrices( camera.projectionMatrix, _viewMatrix );
    
            _frustum.setFromMatrix( _viewProjectionMatrix );
    
            //
    
            _objectCount = 0;
    
            _renderData.objects.length = 0;
            _renderData.lights.length = 0;
    
            projectObject( scene );
    
            if ( sortObjects === true ) {
    
                _renderData.objects.sort( painterSort );
    
            }
    
            //
    
            var objects = _renderData.objects;
    
            for ( var o = 0, ol = objects.length; o < ol; o ++ ) {
    
                var object = objects[ o ].object;
                var geometry = object.geometry;
    
                renderList.setObject( object );
    
                _modelMatrix = object.matrixWorld;
    
                _vertexCount = 0;
    
                if ( object instanceof THREE.Mesh ) {
    
                    if ( geometry instanceof THREE.BufferGeometry ) {
    
                        var attributes = geometry.attributes;
                        var groups = geometry.groups;
    
                        if ( attributes.position === undefined ) continue;
    
                        var positions = attributes.position.array;
    
                        for ( var i = 0, l = positions.length; i < l; i += 3 ) {
    
                            renderList.pushVertex( positions[ i ], positions[ i + 1 ], positions[ i + 2 ] );
    
                        }
    
                        if ( attributes.normal !== undefined ) {
    
                            var normals = attributes.normal.array;
    
                            for ( var i = 0, l = normals.length; i < l; i += 3 ) {
    
                                renderList.pushNormal( normals[ i ], normals[ i + 1 ], normals[ i + 2 ] );
    
                            }
    
                        }
    
                        if ( attributes.uv !== undefined ) {
    
                            var uvs = attributes.uv.array;
    
                            for ( var i = 0, l = uvs.length; i < l; i += 2 ) {
    
                                renderList.pushUv( uvs[ i ], uvs[ i + 1 ] );
    
                            }
    
                        }
    
                        if ( geometry.index !== null ) {
    
                            var indices = geometry.index.array;
    
                            if ( groups.length > 0 ) {
    
                                for ( var g = 0; g < groups.length; g ++ ) {
    
                                    var group = groups[ g ];
    
                                    for ( var i = group.start, l = group.start + group.count; i < l; i += 3 ) {
    
                                        renderList.pushTriangle( indices[ i ], indices[ i + 1 ], indices[ i + 2 ] );
    
                                    }
    
                                }
    
                            } else {
    
                                for ( var i = 0, l = indices.length; i < l; i += 3 ) {
    
                                    renderList.pushTriangle( indices[ i ], indices[ i + 1 ], indices[ i + 2 ] );
    
                                }
    
                            }
    
                        } else {
    
                            for ( var i = 0, l = positions.length / 3; i < l; i += 3 ) {
    
                                renderList.pushTriangle( i, i + 1, i + 2 );
    
                            }
    
                        }
    
                    } else if ( geometry instanceof THREE.Geometry ) {
    
                        var vertices = geometry.vertices;
                        var faces = geometry.faces;
                        var faceVertexUvs = geometry.faceVertexUvs[ 0 ];
    
                        _normalMatrix.getNormalMatrix( _modelMatrix );
    
                        var material = object.material;
    
                        var isMultiMaterial = Array.isArray( material );
    
                        for ( var v = 0, vl = vertices.length; v < vl; v ++ ) {
    
                            var vertex = vertices[ v ];
    
                            _vector3.copy( vertex );
    
                            if ( material.morphTargets === true ) {
    
                                var morphTargets = geometry.morphTargets;
                                var morphInfluences = object.morphTargetInfluences;
    
                                for ( var t = 0, tl = morphTargets.length; t < tl; t ++ ) {
    
                                    var influence = morphInfluences[ t ];
    
                                    if ( influence === 0 ) continue;
    
                                    var target = morphTargets[ t ];
                                    var targetVertex = target.vertices[ v ];
    
                                    _vector3.x += ( targetVertex.x - vertex.x ) * influence;
                                    _vector3.y += ( targetVertex.y - vertex.y ) * influence;
                                    _vector3.z += ( targetVertex.z - vertex.z ) * influence;
    
                                }
    
                            }
    
                            renderList.pushVertex( _vector3.x, _vector3.y, _vector3.z );
    
                        }
    
                        for ( var f = 0, fl = faces.length; f < fl; f ++ ) {
    
                            var face = faces[ f ];
    
                            material = isMultiMaterial === true
                                 ? object.material[ face.materialIndex ]
                                 : object.material;
    
                            if ( material === undefined ) continue;
    
                            var side = material.side;
    
                            var v1 = _vertexPool[ face.a ];
                            var v2 = _vertexPool[ face.b ];
                            var v3 = _vertexPool[ face.c ];
    
                            if ( renderList.checkTriangleVisibility( v1, v2, v3 ) === false ) continue;
    
                            var visible = renderList.checkBackfaceCulling( v1, v2, v3 );
    
                            if ( side !== THREE.DoubleSide ) {
    
                                if ( side === THREE.FrontSide && visible === false ) continue;
                                if ( side === THREE.BackSide && visible === true ) continue;
    
                            }
    
                            _face = getNextFaceInPool();
    
                            _face.id = object.id;
                            _face.v1.copy( v1 );
                            _face.v2.copy( v2 );
                            _face.v3.copy( v3 );
    
                            _face.normalModel.copy( face.normal );
    
                            if ( visible === false && ( side === THREE.BackSide || side === THREE.DoubleSide ) ) {
    
                                _face.normalModel.negate();
    
                            }
    
                            _face.normalModel.applyMatrix3( _normalMatrix ).normalize();
    
                            var faceVertexNormals = face.vertexNormals;
    
                            for ( var n = 0, nl = Math.min( faceVertexNormals.length, 3 ); n < nl; n ++ ) {
    
                                var normalModel = _face.vertexNormalsModel[ n ];
                                normalModel.copy( faceVertexNormals[ n ] );
    
                                if ( visible === false && ( side === THREE.BackSide || side === THREE.DoubleSide ) ) {
    
                                    normalModel.negate();
    
                                }
    
                                normalModel.applyMatrix3( _normalMatrix ).normalize();
    
                            }
    
                            _face.vertexNormalsLength = faceVertexNormals.length;
    
                            var vertexUvs = faceVertexUvs[ f ];
    
                            if ( vertexUvs !== undefined ) {
    
                                for ( var u = 0; u < 3; u ++ ) {
    
                                    _face.uvs[ u ].copy( vertexUvs[ u ] );
    
                                }
    
                            }
    
                            _face.color = face.color;
                            _face.material = material;
    
                            _face.z = ( v1.positionScreen.z + v2.positionScreen.z + v3.positionScreen.z ) / 3;
                            _face.renderOrder = object.renderOrder;
    
                            _renderData.elements.push( _face );
    
                        }
    
                    }
    
                } else if ( object instanceof THREE.Line ) {
    
                    _modelViewProjectionMatrix.multiplyMatrices( _viewProjectionMatrix, _modelMatrix );
    
                    if ( geometry instanceof THREE.BufferGeometry ) {
    
                        var attributes = geometry.attributes;
    
                        if ( attributes.position !== undefined ) {
    
                            var positions = attributes.position.array;
    
                            for ( var i = 0, l = positions.length; i < l; i += 3 ) {
    
                                renderList.pushVertex( positions[ i ], positions[ i + 1 ], positions[ i + 2 ] );
    
                            }
    
                            if ( attributes.color !== undefined ) {
    
                                var colors = attributes.color.array;
    
                                for ( var i = 0, l = colors.length; i < l; i += 3 ) {
    
                                    renderList.pushColor( colors[ i ], colors[ i + 1 ], colors[ i + 2 ] );
    
                                }
    
                            }
    
                            if ( geometry.index !== null ) {
    
                                var indices = geometry.index.array;
    
                                for ( var i = 0, l = indices.length; i < l; i += 2 ) {
    
                                    renderList.pushLine( indices[ i ], indices[ i + 1 ] );
    
                                }
    
                            } else {
    
                                var step = object instanceof THREE.LineSegments ? 2 : 1;
    
                                for ( var i = 0, l = ( positions.length / 3 ) - 1; i < l; i += step ) {
    
                                    renderList.pushLine( i, i + 1 );
    
                                }
    
                            }
    
                        }
    
                    } else if ( geometry instanceof THREE.Geometry ) {
    
                        var vertices = object.geometry.vertices;
    
                        if ( vertices.length === 0 ) continue;
    
                        v1 = getNextVertexInPool();
                        v1.positionScreen.copy( vertices[ 0 ] ).applyMatrix4( _modelViewProjectionMatrix );
    
                        var step = object instanceof THREE.LineSegments ? 2 : 1;
    
                        for ( var v = 1, vl = vertices.length; v < vl; v ++ ) {
    
                            v1 = getNextVertexInPool();
                            v1.positionScreen.copy( vertices[ v ] ).applyMatrix4( _modelViewProjectionMatrix );
    
                            if ( ( v + 1 ) % step > 0 ) continue;
    
                            v2 = _vertexPool[ _vertexCount - 2 ];
    
                            _clippedVertex1PositionScreen.copy( v1.positionScreen );
                            _clippedVertex2PositionScreen.copy( v2.positionScreen );
    
                            if ( clipLine( _clippedVertex1PositionScreen, _clippedVertex2PositionScreen ) === true ) {
    
                                // Perform the perspective divide
                                _clippedVertex1PositionScreen.multiplyScalar( 1 / _clippedVertex1PositionScreen.w );
                                _clippedVertex2PositionScreen.multiplyScalar( 1 / _clippedVertex2PositionScreen.w );
    
                                _line = getNextLineInPool();
    
                                _line.id = object.id;
                                _line.v1.positionScreen.copy( _clippedVertex1PositionScreen );
                                _line.v2.positionScreen.copy( _clippedVertex2PositionScreen );
    
                                _line.z = Math.max( _clippedVertex1PositionScreen.z, _clippedVertex2PositionScreen.z );
                                _line.renderOrder = object.renderOrder;
    
                                _line.material = object.material;
    
                                if ( object.material.vertexColors === THREE.VertexColors ) {
    
                                    _line.vertexColors[ 0 ].copy( object.geometry.colors[ v ] );
                                    _line.vertexColors[ 1 ].copy( object.geometry.colors[ v - 1 ] );
    
                                }
    
                                _renderData.elements.push( _line );
    
                            }
    
                        }
    
                    }
    
                } else if ( object instanceof THREE.Points ) {
    
                    _modelViewProjectionMatrix.multiplyMatrices( _viewProjectionMatrix, _modelMatrix );
    
                    if ( geometry instanceof THREE.Geometry ) {
    
                        var vertices = object.geometry.vertices;
    
                        for ( var v = 0, vl = vertices.length; v < vl; v ++ ) {
    
                            var vertex = vertices[ v ];
    
                            _vector4.set( vertex.x, vertex.y, vertex.z, 1 );
                            _vector4.applyMatrix4( _modelViewProjectionMatrix );
    
                            pushPoint( _vector4, object, camera );
    
                        }
    
                    } else if ( geometry instanceof THREE.BufferGeometry ) {
    
                        var attributes = geometry.attributes;
    
                        if ( attributes.position !== undefined ) {
    
                            var positions = attributes.position.array;
    
                            for ( var i = 0, l = positions.length; i < l; i += 3 ) {
    
                                _vector4.set( positions[ i ], positions[ i + 1 ], positions[ i + 2 ], 1 );
                                _vector4.applyMatrix4( _modelViewProjectionMatrix );
    
                                pushPoint( _vector4, object, camera );
    
                            }
    
                        }
    
                    }
    
                } else if ( object instanceof THREE.Sprite ) {
    
                    _vector4.set( _modelMatrix.elements[ 12 ], _modelMatrix.elements[ 13 ], _modelMatrix.elements[ 14 ], 1 );
                    _vector4.applyMatrix4( _viewProjectionMatrix );
    
                    pushPoint( _vector4, object, camera );
    
                }
    
            }
    
            if ( sortElements === true ) {
    
                _renderData.elements.sort( painterSort );
    
            }
    
            return _renderData;
    
        };
    
        function pushPoint( _vector4, object, camera ) {
    
            var invW = 1 / _vector4.w;
    
            _vector4.z *= invW;
    
            if ( _vector4.z >= - 1 && _vector4.z <= 1 ) {
    
                _sprite = getNextSpriteInPool();
                _sprite.id = object.id;
                _sprite.x = _vector4.x * invW;
                _sprite.y = _vector4.y * invW;
                _sprite.z = _vector4.z;
                _sprite.renderOrder = object.renderOrder;
                _sprite.object = object;
    
                _sprite.rotation = object.rotation;
    
                _sprite.scale.x = object.scale.x * Math.abs( _sprite.x - ( _vector4.x + camera.projectionMatrix.elements[ 0 ] ) / ( _vector4.w + camera.projectionMatrix.elements[ 12 ] ) );
                _sprite.scale.y = object.scale.y * Math.abs( _sprite.y - ( _vector4.y + camera.projectionMatrix.elements[ 5 ] ) / ( _vector4.w + camera.projectionMatrix.elements[ 13 ] ) );
    
                _sprite.material = object.material;
    
                _renderData.elements.push( _sprite );
    
            }
    
        }
    
        // Pools
    
        function getNextObjectInPool() {
    
            if ( _objectCount === _objectPoolLength ) {
    
                var object = new THREE.RenderableObject();
                _objectPool.push( object );
                _objectPoolLength ++;
                _objectCount ++;
                return object;
    
            }
    
            return _objectPool[ _objectCount ++ ];
    
        }
    
        function getNextVertexInPool() {
    
            if ( _vertexCount === _vertexPoolLength ) {
    
                var vertex = new THREE.RenderableVertex();
                _vertexPool.push( vertex );
                _vertexPoolLength ++;
                _vertexCount ++;
                return vertex;
    
            }
    
            return _vertexPool[ _vertexCount ++ ];
    
        }
    
        function getNextFaceInPool() {
    
            if ( _faceCount === _facePoolLength ) {
    
                var face = new THREE.RenderableFace();
                _facePool.push( face );
                _facePoolLength ++;
                _faceCount ++;
                return face;
    
            }
    
            return _facePool[ _faceCount ++ ];
    
    
        }
    
        function getNextLineInPool() {
    
            if ( _lineCount === _linePoolLength ) {
    
                var line = new THREE.RenderableLine();
                _linePool.push( line );
                _linePoolLength ++;
                _lineCount ++;
                return line;
    
            }
    
            return _linePool[ _lineCount ++ ];
    
        }
    
        function getNextSpriteInPool() {
    
            if ( _spriteCount === _spritePoolLength ) {
    
                var sprite = new THREE.RenderableSprite();
                _spritePool.push( sprite );
                _spritePoolLength ++;
                _spriteCount ++;
                return sprite;
    
            }
    
            return _spritePool[ _spriteCount ++ ];
    
        }
    
        //
    
        function painterSort( a, b ) {
    
            if ( a.renderOrder !== b.renderOrder ) {
    
                return a.renderOrder - b.renderOrder;
    
            } else if ( a.z !== b.z ) {
    
                return b.z - a.z;
    
            } else if ( a.id !== b.id ) {
    
                return a.id - b.id;
    
            } else {
    
                return 0;
    
            }
    
        }
    
        function clipLine( s1, s2 ) {
    
            var alpha1 = 0, alpha2 = 1,
    
            // Calculate the boundary coordinate of each vertex for the near and far clip planes,
            // Z = -1 and Z = +1, respectively.
    
                bc1near = s1.z + s1.w,
                bc2near = s2.z + s2.w,
                bc1far = - s1.z + s1.w,
                bc2far = - s2.z + s2.w;
    
            if ( bc1near >= 0 && bc2near >= 0 && bc1far >= 0 && bc2far >= 0 ) {
    
                // Both vertices lie entirely within all clip planes.
                return true;
    
            } else if ( ( bc1near < 0 && bc2near < 0 ) || ( bc1far < 0 && bc2far < 0 ) ) {
    
                // Both vertices lie entirely outside one of the clip planes.
                return false;
    
            } else {
    
                // The line segment spans at least one clip plane.
    
                if ( bc1near < 0 ) {
    
                    // v1 lies outside the near plane, v2 inside
                    alpha1 = Math.max( alpha1, bc1near / ( bc1near - bc2near ) );
    
                } else if ( bc2near < 0 ) {
    
                    // v2 lies outside the near plane, v1 inside
                    alpha2 = Math.min( alpha2, bc1near / ( bc1near - bc2near ) );
    
                }
    
                if ( bc1far < 0 ) {
    
                    // v1 lies outside the far plane, v2 inside
                    alpha1 = Math.max( alpha1, bc1far / ( bc1far - bc2far ) );
    
                } else if ( bc2far < 0 ) {
    
                    // v2 lies outside the far plane, v2 inside
                    alpha2 = Math.min( alpha2, bc1far / ( bc1far - bc2far ) );
    
                }
    
                if ( alpha2 < alpha1 ) {
    
                    // The line segment spans two boundaries, but is outside both of them.
                    // (This can't happen when we're only clipping against just near/far but good
                    //  to leave the check here for future usage if other clip planes are added.)
                    return false;
    
                } else {
    
                    // Update the s1 and s2 vertices to match the clipped line segment.
                    s1.lerp( s2, alpha1 );
                    s2.lerp( s1, 1 - alpha2 );
    
                    return true;
    
                }
    
            }
    
        }
    
    };