> Quote - How did *they* get such a smooth result?

 

Perhaps they didn't use IDL in those pictures? Perhaps there is no environment or, at least, no geometry right next to the pointlight's location.

 

Inverse Square Fall-off is not completely "broken" as you put it, but rather it fails quite badly in certain particular circumstances (as I remember pointing out to you when you asked the same question elsewhere last week). If you keep those circumstances in mind and avoid them or put in very simple measures to counteract the problems of those circumstances, everything's fine.

 

The attached picture is lit using only an ISF pointlight and IDL.

The pointlight is set to 40% intensity and is positioned less than an inch below the slightly off-white ceiling. How did I avoid the speckles? A square positioned between the light and the ceiling, and set to pure black so that none of the ceiling that's in the light's "ISF hot zone" is available to bounce that light back into the scene. I did a render without the black square and, sure enough, the speckles appeared.