{ width: 300 } );

			gui.add( params, 'branchingFactor', 2, 6 ).step( 1 ).onChange( createBVH );
			gui.add( params, 'primitivesPerNode', 1, 10 ).step( 1 ).onChange( createBVH );
			gui.add( params, 'depth', 1, 8 ).step( 1 ).onChange( createBVH );
			gui.add( params, 'meshVisible' ).onChange( ( value ) => icoSphere.visible = value );

			gui.open();

			// bvh setup

			const threeGeometry = sphereGeometry.clone();
			threeGeometry.applyMatrix( icoSphere.matrix ); // transform vertices to world space

			c