g) {
    return deg * Math.PI / 180;
  }

  var clock = 0;
  var frameCount = 0;
  function render(elapsedTime) {
    clock += elapsedTime;
    ++frameCount;

    // clear the screen.
    gl.enable(gl.DEPTH_TEST);
//    gl.colorMask(true, true, true, true);
//    gl.clearColor(1, 1, 1, 1);
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    var aspect = canvas.clientWidth / canvas.clientHeight;
    m4.perspective(
        degToRad(40),
        aspect,
        1,
        5000,
        projection);
