It's the fix for this bug that is causing the long render time:
https://projects.blender.org/tracker/index.php?func=detail&aid=29723

This fixed wrong refraction in some cases, and the new version should render more correct results, but at the same time it needs many more rays. Setting depth to 21 is problematic for Blender Internal, it can result in up to 2^21 = 2 million rays per pixel if surfaces have both refraction and mirror reflection and the ray fails to exit the object due to total internal reflection.

I think the only good way to support depth that high is monte carlo path tracing: random picking between reflection/refraction, and random path termination. That goes beyond what counts as a bug though, it would be a new feature. All I can suggest at the moment is to lower the depth here.

Thanks for reply. I tried r59453M, and not use raytrace material, but same problem occurs.

Example in r59453M version:

* I disable all Raytrace options: Shadow, Mirror, AO etc.

* I disable Compositing.

* Clear all materials on "Diamond" and "Plane".

* Hit F12 for Render, but program still not response.


When this response problem fix, then I'll try lower depth values.

I suspect what you're seeing is that the preview render is stuck, for the diamond the texture preview render is set to show the material, and so it will actually try to render with this depth before you disable it.

Anyway, cancelling the final and preview render should be possible even if it is this slow, that I can fix.

Fix for that now in revision 59472, the preview render should no longer cause Blender to hang, and the final render can be cancelled as well now.

Thanks for fix.

I tried r59489M revision and render respond problem fixed.

And try same scene for "Depth = 10". Render Time = "00:49.57"

Try same scene for "Depth = 21" in Blender 2.61. Render Time = "00:13.96"

And Raytrace quality in 2.68 good as 2.61, but slow.

I hope Blender's new versions would increase raytrace performance.

Right, but that's no a valid comparison, the resulting render is different.

In 2.61 most rays would exit the object after only a few bounces so you weren't actually getting depth 21.

Yes, 2.68 result is good as 2.61.

What is guide for select true depth value in 2.68? There is not tutorial site, i know, but I wonder it? Any formula? (please won't be complex :)) Or any tip?

Higher depth gives more accurate results, in reality the depth would be infinite. It depends on what you want to render, you can set it as low as you can while you're still happy with the way it looks.

Thanks.