k3d/share/shaders/k3d_crayon.sl:18:	density0 - controls the amount of topcolor seen - measured as a proportion - 
k3d/share/shaders/k3d_crayon.sl:19:		this should vary between 0 (no topcolor) to 1, .3 would give 30% topcolor;
k3d/share/shaders/k3d_crayon.sl:23:	color topcolor, basecolor - the color of the crayon strokes and the color of the ground
k3d/share/shaders/k3d_crayon.sl:66:			color topcolor = 1;
k3d/share/shaders/k3d_crayon.sl:89:	Csurf = mix(basecolor, topcolor, m);
