k3d/share/shaders/k3d_superplank.sl:28: *   ringwidth - relative width of the dark ring parts
k3d/share/shaders/k3d_superplank.sl:76:			float ringwidth = 1;	/* Relative ring width */
k3d/share/shaders/k3d_superplank.sl:222:	0.3 + 0.7 * smoothstep(.55 - .35 * ringwidth, 0.55,
