Microsoft Windows 7 Home Premium
16GB 1600MHz RAM
Broken: 2.70, 2.71RC2
Worked: None yet.
While following the Pancake Hobo tutorial on Blender Cookie, I was following along with my GPU as render device, using fake SSS shaders. However, near the end, after adding a refraction shader as part of the material for the syrup, I ran into problems. The render crashed because of a timeout, and when I edited the registry setting that controls it, the render was taking a very long time - 5 samples per second on the white background.
1: Open the file, enter viewport render. Notice that it works well enough.
2: Attempt an f12 render, using CUDA. Blender will likely crash due to timeout, and if overriden (as I have done), notice the slow render speeds.
3: Enter the syrup object material, and enter the Refractive Absorption nodegroup. Try removing the Light Path node; no change (there was not long ago a bug that affected using Light Path in materials with the GPU). Replace the refraction shader with a Transluscent shader, inputting the color with the Light Path node on the other end of the string.
4: Now, try another f12 render. Notice that it has sped up considerably, with no crashes.
-The SSS shaders for the other objects are faked with a diffuse and two transluscent shaders each.
-When rendering with No Causics enabled, and the refraction shader in place, the render goes back to a decent speed.
-All textures are Creative Commons.
-The attached file is large, but the only one where I can easily recreate the issue.