leave trails snippet, for threejs_playGnd

trails.js

  	/* ------------------- INSTRUCTIONS -----

	to leave trails
	replace the 'renderer = new ...' on line 27
	in the setup() function, with the code below

	-------------------------------------- */

	renderer = new THREE.WebGLRenderer( { preserveDrawingBuffer: true } );
	renderer.autoClearColor = false;
        
        /* -------------------------------------- 
        to see this in action, move and/or spin
        your mesh, add the code below to your
        draw() function
        -------------------------------------- */
        mesh.position.x = Math.sin( Date.now() * 0.001 ) * 50;  
	mesh.rotation.z = Date.now() * 0.0005;