k3d/share/shaders/k3d_crayon.sl:18:	density0 - controls the amount of topcolor seen - measured as a proportion - 
k3d/share/shaders/k3d_crayon.sl:20:	density1 - if different density0 this is the density when t = 1, with a smooth
k3d/share/shaders/k3d_crayon.sl:21:		interpolation of values for density0 when t = 0, thus allowing a 
k3d/share/shaders/k3d_crayon.sl:64:			float density0 = .5;
k3d/share/shaders/k3d_crayon.sl:71:    float density = density0 + t * (density1 - density0);
