Dear All,
In my scene I have a candle with SSS, a pair of swords, both reflective and of course the bounding box to have something to reflect and to help in the use of GI.
As I have a rather weak system and because of the sheer size of the scene I’m forced to use CPU - giving an even slower render time, I did the following:
I reduced ray bounces to 32 instead of the 128 default
I increased the “rendering box” sizes from the default 64 to 256.
I have a 687 or so sample count.
However, I saw that there are some checkerboxes, namely reflective and refractive caustics.
When I was using Maya with mental ray, we needed caustics only when dealing with e.g. glass or water, so transparent or refractive materials and it bumped up render time significantly due to photon emission calculations. The information pop up says they brighten up the scene but generate noise.
I would like to ask you if one needs those options in a scene with no glass, water, crystals or transparency but with a lot of reflection?
Thank you in advance for your help.
Those values work with the overall max depth settings, you get whichever value is lower for that ray type. So if you have max=12, diffuse=4, glossy=16, you get 12 glossy bounces and 4 diffuse bounces. You can set these much lower, btw. I’d try the “limited global illumination” preset to start
I increased the “rendering box” sizes from the default 64 to 256.
The tile size? Why? Normally 32 or 16 works better for CPU.
However, I saw that there are some checkerboxes, namely reflective and refractive caustics.
When I was using Maya with mental ray, we needed caustics only when dealing with e.g. glass or water, so transparent or refractive materials and it bumped up render time significantly due to photon emission calculations. The information pop up says they brighten up the scene but generate noise.
I would like to ask you if one needs those options in a scene with no glass, water, crystals or transparency but with a lot of reflection?
Thank you in advance for your help.
In Mental Ray you need to do some extra calculations (caustic photons) to generate caustics. Cycles doesn’t do that, it just lets them happen while doing GI calculations. This can add a lot of noise in some cases, so those checkboxes will tell Cycles to abort a path if it becomes a caustic (specular bounce followed by a diffuse bounce). So if your scene contains no refraction shaders, toggling refractive caustics does nothing, because the abort case never occurs.
The best thing to do with those checkboxes is just test them with the viewport render. Switch your viewport to rendered, and flip them on and off, see what the results look like. Depending on the scene, it might not be much of a difference, so don’t think you’re missing something if nothing changes.
Thanks for taking the time to help me out.
I got the idea of increasing the tile size to 256 from a Pluralsight tutorial. The lad’s prior render took 15 mins, the after took 5 mins.
Do you think I should rather decrease their size to 32?
As for the checkboxes, you answered my question perfectly, thank you.
GPU render mode likes big tiles (256 or 512px, or even larger). CPU render mode likes small tiles, 32 or 16px. The default tile size is a compromise for CPU and GPU. There’s an addon called “auto tile size”, I believe it’s bundled with Blender, you can find it under user preferences > addons. It will help manage tile size settings in Cycles for you.