CPU rendering = better accuracy?

Hi

New to Blender and 3D in general, but have a good background in other aspects of computing.

I’ve been doing lots of reading about CPU vs GPU, and realize that rendering with a Geforce card produces the fastest results. However, most of the comparisons focus exclusively on rendering speed and not accuracy/quality of the final image. So I have some questions in this regard.

  1. From what I’ve seen, the output differs between images rendered with a CPU and those rendered with a GPU, with the CPU image being ‘better quality’?!? Is this the case with Blender Cycles? And does it apply to other renderers as well? I’m aware of some of the limitations of GPU rendering, such as smoke etc., but overall, what else is affected - if anything?

  2. Is there a similar accuracy/quality difference between Geforce vs Quadro output other than speed?

Can someone post or point to renderings of test scenes to answer these questions? I’d try this myself, but only have HD4000 graphics at the moment, so can’t do it.

Any help on this topic will greatly help me spec a new system. I’m planning on doing mainly architectural stuff and interiors. Speed for final render is not really an issue.

Thanks in advance!

  1. There shouldn’t be any difference between GPU and CPU. There can be differences in capability, for instance, Cycles GPU can not render smoke/fire. Using the CPU means that Cycles has more memory to use, but none of these things should affect the quality of the image.

  2. The Quadro’s use the same chip that the Geforce cards use, the only difference is that the Quadro chips tested out better when they were manufactured. The other differences between Quadro and Geforce cards is in the drivers and the use of ECC memory. The main issue with Quadro cards is the driver as it’s more optimized for double precision and OpenGL.

I don’t know AMD cards very well, but you might want to wait for the new modified kernel that works with these cards and see if your current card will work. If you want a new card you should get one with as much vram as you can. Until Cycles get some kind of “out of core” memory features you will need as much memory as you can get. This is true for AMD and Nvidia cards, although get a Nvidia card if you need to do GPU rendering right now. It’s going to be awhile before Cycles is going to be real useful with AMD cards.

There are different optimizations that happen on GPU compared to CPU… the differences are subtle but are definitely noticeable… especially with volumetrics / hair.

I didn’t know that, thanks. :slight_smile:

This is precisely what I’m interested in. Could you post some examples?