k3d/share/shaders/k3d_craters.sl:22:   float jitter=1.0;     /* irregularity of crater spacing */
k3d/share/shaders/k3d_starfield.sl:11:surface k3d_starfield(float intensity = 2.0; float frequency = 0.1; float size = 0.3; float irregularity = 2.0)
k3d/share/shaders/k3d_starfield.sl:19:	star_center += irregularity * (point noise(star_center) - point(0.5, 0.5, 0.5));
