k3d/share/shaders/k3d_superplank.sl:90:  float sw, tw, overallscale;
k3d/share/shaders/k3d_superplank.sl:137:  overallscale = (length(Deriv(P, ss)));
k3d/share/shaders/k3d_superplank.sl:280:      shadlen = overallscale / length(ntransform("shader", NN));
