Caustics - problem for high value of IOR

[hrisek]

For IOR (refraction) greater than 4.0 caustics are hanging my 3d max (PT + PT). For PT+HD only HD is going good, but than "rendering initial pass" is looking like paused after first 2 minutes.... Corona renderer is still busy, no new pixels in renderer windows...i waited 15 mintues - rendering didn't started. Is it to big value for caustics to calculate photons? Maybe it's physical correct because i don't know materials with so high IOR for refractive (diamond is 2.419).

[Ondra]

You can send the scene to make sure there is no bug, but I can easily see why this would happen: if you have large IOR, lots of light get trapped inside the objects for many bonuces because of total internal reflection. There is more total internal reflection going on with higher IOR. This is what causes the diamond optical properties, but can also be hard to simulate, because extra bounces are needed.

[hrisek]

I uploaded file "Corona_Render_Caustics_tests.max", 3D max 2012 64 bit file.
Actually IOR is 5.0. Your explanation sounds like physical correct model for these case.

[Ondra]

Oh, I did not expect so huge slowdown. There was a small detail that exploded when given this specific scene and physically unplausible material and caused HUGE increase in sampling quality. I've fixed it

[hrisek]

Sorry for problem...i just wanted to test some extreme situations...

[Ondra]

thats allright, I am happy to fix such bugs