k3d/share/shaders/k3d_volcube.sl:11:   SurfNormalDepth     - the mixing depth from surface
k3d/share/shaders/k3d_volcube.sl:194:	     float  SurfNormalDepth = .05;
k3d/share/shaders/k3d_volcube.sl:248:		    Nf = fnc_normalMix(Nf,Vol_Nf,clamp(cur_depth/SurfNormalDepth,0,1));
