k3d/share/shaders/k3d_eyeball.sl:17: *   pupilsize - size of pupil (in "t" space)
k3d/share/shaders/k3d_eyeball.sl:18: *   irissize - size of iris (in "t" space), must be larger than pupilsize
k3d/share/shaders/k3d_eyeball.sl:54:	 float pupilsize = 0.05, irissize = 0.12;
k3d/share/shaders/k3d_eyeball.sl:84:  pupilstat = smoothstep (pupilsize, pupilsize+twidth, tt);
