k3d/share/shaders/k3d_cloudplane.sl:27:    float y, fy, yfreq, yphase;
k3d/share/shaders/k3d_cloudplane.sl:37:    yphase = 0.7; /* arbitrary */
k3d/share/shaders/k3d_cloudplane.sl:46:            (offset + cos(yfreq * (y + yphase)));
k3d/share/shaders/k3d_cloudplane.sl:49:        yphase = PI/2 * 1.1 * cos(xfreq * x);
