GPU and CPU rendering issues

[KPSWD]

I am relatively new to rendering so bear with me...

I have a new workstation with an Nvidia M4000 GPU. I don't use interactive render, I don't really find it useful, but I expected that the Nvidia CUDA GPU would perform faster and give better render results than using the Core i7 CPU for production renders. It seems I am wrong. This is the GPU render of a partially built scene:


Note the poor quality transparency of the tree (a 2D billboard) at the back.

This is the CPU render (no other settings changed)


The transparency is much better, oddly some colours have changed (palm tree left of centre is blue-green in GPU output, dark green in CPU output).


It seems I should have gone for a multiple CPU based machine, and not bothered too much about the GPU... expensive mistake?

[Svetlozar Draganov]

GPU rendering still have less supported features that CPU. This doesn't mean a bad quality but things like the transparency of the tree that renders wrong. We are constantly improving GPU engine so such issues will be less prominent in the future, I wouldn't surprise if this is already resolved. If it is not with the latest version I would recommend you send us all the details from the scene that renders quite different than the CPU engine.

Since CPU and GPU are two different engines some small color deviations is considered as normal, a large discrepancies however should be investigated in case they are bugs or something else.

I don't think GPU investment is a mistake, GPU rendering is usually faster and with the upcoming Hybrid Rendering you will be able to use both CPU and GPU at the same time which would give even faster render times.