rial( { color: RAY_COLOR } ),
					2 * MAX_RAYS
				);
				sphereInstance.instanceMatrix.setUsage( THREE.DynamicDrawUsage );
				sphereInstance.count = 0;

				scene.add( sphereInstance, lineSegments );

				// load the bunny
				const loader = new FBXLoader();
				loader.load( 'models/fbx/stanford-bunny.fbx', object => {

					mesh = object.children[ 0 ];

					const geometry = mesh.geometry;
					geometry.translate( 0, 0.5 / 0.0075, 0 );
					geometry.computeBoundsTree();
					bvh = geometry.boundsTree;

