/**
     * creates a new reflection matrix about this plane.
     */
    export function createReflectionMatrix(plane: THREE.Plane) : THREE.Matrix4 {
        var n = plane.normalize()
        var m = new THREE.Matrix4()
        return m.set(
            -1.0 - 2.0 * n.normal.x * n.normal.x, // negated?
            -2.0 * n.normal.x * n.normal.y,
            -2.0 * n.normal.x * n.normal.z,
             0.0,
            -2.0 * n.normal.x * n.normal.y,
             1.0 - 2.0 * n.normal.y * n.normal.y,
            -2.0 * n.normal.y * n.normal.z,
             0.0,
            -2.0 * n.normal.z * n.normal.x,
            -2.0 * n.normal.z * n.normal.y,
             1.0 - 2.0 * n.normal.z * n.normal.z,
             0.0,
            -2.0 * n.constant * n.normal.x,
            -2.0 * n.constant * n.normal.y,
            -2.0 * n.constant * n.normal.z,
             1.0);
    }


    /**
     * mirrors this camera about a plane.
     * @param camera {THREE.Camera} the camera to mirror
     * @param plane {THREE.Plane} the plane to mirror against.
     * @returns {THREE.Camera} a new camera mirrored against this plane.
     */
    export function reflect(camera: THREE.PerspectiveCamera, plane: THREE.Plane) : THREE.Camera {
        var reflect = camera.clone()
        plane = new THREE.Plane(new THREE.Vector3(0, 1, 0), 0)
        reflect.matrixAutoUpdate = false;
        reflect.matrix.identity()
        reflect.matrix.multiply(acid.graphics.math.createReflectionMatrix(plane))
        reflect.matrix.multiply(camera.matrix)
        reflect.updateProjectionMatrix();
        reflect.updateMatrixWorld(true);
        return reflect;
    }