k3d/share/shaders/k3d_cloudplane.sl:26:    float x, fx, xfreq, xphase;
k3d/share/shaders/k3d_cloudplane.sl:36:    xphase = 0.9; /* arbitrary */
k3d/share/shaders/k3d_cloudplane.sl:44:            (offset + cos(xfreq * (x + xphase)));
k3d/share/shaders/k3d_cloudplane.sl:48:        xphase = PI/2 * 0.9 * cos(yfreq * y);
