k3d/share/shaders/k3d_contacshadow.sl:34:    point screenP = transform(matNP, P);  
k3d/share/shaders/k3d_contacshadow.sl:35:    float ss = (xcomp(screenP) + 1) * 0.5;  
k3d/share/shaders/k3d_contacshadow.sl:36:    float tt = (1 - ycomp(screenP)) * 0.5;  
