projectPlanes( source, destination, offset ) {

		const l = source.length;

		for ( let i = 0; i < l; i ++ ) {

			_plane.copy( source[ i ] ).applyMatrix4( this.viewMatrix, this.viewNormalMatrix );

			const v = destination[ offset + i ];
			const normal = _plane.normal;

			v.x = - normal.x;
			v.y = - normal.y;
			v.z = - normal.z;
			v.w = _plane.constant;

		}

	}
Projects the given source clipping planes and writes the result into the
destination array.

@param {Array<Plane>} source - The source clipping planes.
@param {Array<Vector4>} destination - The destination.
@param {number} offset - The offset.