 -200, 0];
    var target = [0, 0, 0];
    var up = [0, 0, 1];
    var cameraMatrix = m4.lookAt(cameraPosition, target, up);

    // Make a view matrix from the camera matrix.
    var viewMatrix = m4.inverse(cameraMatrix);

    var viewProjectionMatrix = m4.multiply(projectionMatrix, viewMatrix);

    // update the local matrices for each object.
    m4.multiply(m4.yRotation(0.01), sunNode.localMatrix  , sunNode.localMatrix);
    m4.multiply(m4.yRotation(0.01), earthNode.localMatrix, earthNode.localMatrix);