xRotation(Math.PI), -50, -75, -15);
  //var matrix = m4.xRotate(m4.translation(-50, -75, -15), Math.PI);

  for (var ii = 0; ii < positions.length; ii += 3) {
    var vector = m4.transformPoint(matrix, [positions[ii + 0], positions[ii + 1], positions[ii + 2], 1]);
    positions[ii + 0] = vector[0];
    positions[ii + 1] = vector[1];
    positions[ii + 2] = vector[2];
  }

  gl.bufferData(gl.ARRAY_BUFFER, positions, gl.STATIC_DRAW);
}

// Fill the current ARRAY_BUFFER buffer
// with texture coordinates for t