I decided to add water to the glass from my last post. You would think that would be simple, but it came out black. I made a cutaway of the glass just to make sure that the water itself wasn’t to blame.

I know that Pov-Ray shows coincident surfaces in an odd, randomly speckled texture, because of rounding errors, but this is just straight black. My first thought was that it had something to do with the number of surfaces that each test ray intersects after being shot out from the camera, but even setting the max_intersections parameter as high as 80 did nothing.

Now time to do some research on the POV-Ray newsgroups, maybe a couple other websites, and try tweaking the material properties of the objects.

Update: I removed the ior statement from the drinking glass, and then from the water object, which removes the problem, but they don’t look right without the ior. Interesting, but still not quite helpful.