Ray.js

/**
 * @author mrdoob / http://mrdoob.com/
 */

THREE.Ray = function ( origin, direction, near, far ) {

	this.origin = origin || new THREE.Vector3();
	this.direction = direction || new THREE.Vector3();
	this.near = near || 0;
	this.far = far || Infinity;

	//

	var a = new THREE.Vector3();
	var b = new THREE.Vector3();
	var c = new THREE.Vector3();
	var d = new THREE.Vector3();

	var originCopy = new THREE.Vector3();
	var directionCopy = new THREE.Vector3();
	
	var localOriginCopy = new THREE.Vector3();
	var localDirectionCopy = new THREE.Vector3();


	var vector = new THREE.Vector3();
	var normal = new THREE.Vector3();
	var intersectPoint = new THREE.Vector3();
	
	
	var inverseMatrix = new THREE.Matrix4();

	var descSort = function ( a, b ) {

			return a.distance - b.distance;

	};

	//

	var v0 = new THREE.Vector3(), v1 = new THREE.Vector3(), v2 = new THREE.Vector3();
	var dot, intersect, distance;

	var distanceFromIntersection = function ( origin, direction, position ) {

		v0.sub( position, origin );
		dot = v0.dot( direction );

		intersect = v1.add( origin, v2.copy( direction ).multiplyScalar( dot ) );
		distance = position.distanceTo( intersect );

		return distance;

	}

	// http://www.blackpawn.com/texts/pointinpoly/default.html

	var dot00, dot01, dot02, dot11, dot12, invDenom, u, v;

	var pointInFace3 = function ( p, a, b, c ) {

		v0.sub( c, a );
		v1.sub( b, a );
		v2.sub( p, a );

		dot00 = v0.dot( v0 );
		dot01 = v0.dot( v1 );
		dot02 = v0.dot( v2 );
		dot11 = v1.dot( v1 );
		dot12 = v1.dot( v2 );

		invDenom = 1 / ( dot00 * dot11 - dot01 * dot01 );
		u = ( dot11 * dot02 - dot01 * dot12 ) * invDenom;
		v = ( dot00 * dot12 - dot01 * dot02 ) * invDenom;

		return ( u >= 0 ) && ( v >= 0 ) && ( u + v < 1 );

	}

	//

	var precision = 0.0001;

	this.setPrecision = function ( value ) {

		precision = value;

	};

	this.intersectObject = function ( object, recursive ) {

		var intersect, intersects = [];

		if ( recursive === true ) {

			for ( var i = 0, l = object.children.length; i < l; i ++ ) {

				Array.prototype.push.apply( intersects, this.intersectObject( object.children[ i ], recursive ) );

			}

		}

		if ( object instanceof THREE.Particle ) {

			distance = distanceFromIntersection( this.origin, this.direction, object.matrixWorld.getPosition() );

			if ( distance > object.scale.x ) {

				return [];

			}

			intersect = {

				distance: distance,
				point: object.position,
				face: null,
				object: object

			};

			intersects.push( intersect );

		} else if ( object instanceof THREE.Mesh ) {

			// Checking boundingSphere

			var scale = THREE.Frustum.__v1.set( object.matrixWorld.getColumnX().length(), object.matrixWorld.getColumnY().length(), object.matrixWorld.getColumnZ().length() );
			var scaledRadius = object.geometry.boundingSphere.radius * Math.max( scale.x, Math.max( scale.y, scale.z ) );

			// Checking distance to ray

			distance = distanceFromIntersection( this.origin, this.direction, object.matrixWorld.getPosition() );

			if ( distance > scaledRadius) {

				return intersects;

			}

			// Checking faces

			var f, fl, face, dot, scalar,
			geometry = object.geometry,
			vertices = geometry.vertices,
			objMatrix, geometryMaterials,
			isFaceMaterial, material, side;

			geometryMaterials = object.geometry.materials;
			isFaceMaterial = object.material instanceof THREE.MeshFaceMaterial;
			side = object.material.side;

			object.matrixRotationWorld.extractRotation( object.matrixWorld );
			
			originCopy.copy( this.origin );
			directionCopy.copy( this.direction );

			objMatrix = object.matrixWorld;
			inverseMatrix.getInverse(objMatrix);
			
			
			
			localOriginCopy.copy(originCopy);
			inverseMatrix.multiplyVector3(localOriginCopy);
			
			localDirectionCopy.copy(directionCopy);
			inverseMatrix.rotateAxis(localDirectionCopy).normalize();

			for ( f = 0, fl = geometry.faces.length; f < fl; f ++ ) {

				face = geometry.faces[ f ];

				material = isFaceMaterial === true ? geometryMaterials[ face.materialIndex ] : object.material;
				if ( material === undefined ) continue;

				side = material.side;

				vector.sub( face.centroid, localOriginCopy );
				normal.copy( face.normal );
				dot = localDirectionCopy.dot( normal );


				// bail if ray and plane are parallel

				if ( Math.abs( dot ) < precision ) continue;

				// calc distance to plane

				scalar = normal.dot( vector ) / dot;

				// if negative distance, then plane is behind ray

				if ( scalar < 0 ) continue;

				if ( side === THREE.DoubleSide || ( side === THREE.FrontSide ? dot < 0 : dot > 0 ) ) {

					intersectPoint.add( localOriginCopy, localDirectionCopy.multiplyScalar( scalar ) );

					if ( face instanceof THREE.Face3 ) {

						a.copy( vertices[ face.a ] );
						b.copy( vertices[ face.b ] );
						c.copy( vertices[ face.c ] );

						if ( pointInFace3( intersectPoint, a, b, c ) ) {

							var point = object.matrixWorld.multiplyVector3(intersectPoint.clone()); 
							distance = originCopy.distanceTo( point);
							
							if ( distance < this.near ) continue;
							if ( distance > this.far ) continue; 
							
							
							intersect = {

								distance: distance,
								point: point,
								face: face,
								faceIndex: f,
								object: object

							};

							intersects.push( intersect );

						}

					} else if ( face instanceof THREE.Face4 ) {

						a.copy( vertices[ face.a ] );
						b.copy( vertices[ face.b ] );
						c.copy( vertices[ face.c ] );
						d.copy( vertices[ face.d ] );

						if ( pointInFace3( intersectPoint, a, b, d ) || pointInFace3( intersectPoint, b, c, d ) ) {

							var point = object.matrixWorld.multiplyVector3(intersectPoint.clone()); 
							distance = originCopy.distanceTo( point);
							
							if ( distance < this.near ) continue;
							if ( distance > this.far ) continue; 
							
							intersect = {

								distance: distance,
								point: point,
								face: face,
								faceIndex: f,
								object: object

							};

							intersects.push( intersect );

						}

					}

				}

			}

		}

		intersects.sort( descSort );

		return intersects;

	};

	this.intersectObjects = function ( objects, recursive ) {

		var intersects = [];

		for ( var i = 0, l = objects.length; i < l; i ++ ) {

			Array.prototype.push.apply( intersects, this.intersectObject( objects[ i ], recursive ) );

		}

		intersects.sort( descSort );

		return intersects;

	};

};