		const znear = camera.near;
				return - zfar * znear / ( depth * ( zfar - znear ) - zfar );

			}

			function smoothstep( near, far, depth ) {

				const x = saturate( ( depth - near ) / ( far - near ) );
				return x * x * ( 3 - 2 * x );

			}

			function saturate( x ) {

				return Math.max( 0, Math.min( 1, x ) );

			}

			function render() {

				const time = Date.now() * 0.00015;

				camera.position.x = Math.cos( time ) * 400;
				camera.position.z = Math.sin( time ) * 500;
				camera.position.y =