Why is the GPU mode so fast? :)

[Micha]

Hi,

I'm testing an interior scene and the GI is set to LC/IM progressive. If I use the GPU mode, than after the LC pass a progressive calculation is started. Together with the final denoiser impressive fast! If I switch to CPU than after the LC pass the slow IM pass is started .... .

Now I ask me, where is the IM pass in GPU mode? And is there a way to get the same calculation way for the CPU mode? Should I disable the IM, but what use instead?

-Micha

[Micha]

I think I found the answer - in GPU mode BF is used instead IM. And if I use LC+BF in CPU mode, the speed is lower. Looks like GPU rendering can be a nice speed turbo. (GTX1080ti + GTX780).

[ivan.slavchev]

It rather depends on your hardware. Having a powerful CPU decreases CPU render time, having powerful GPUs decreases GPU render time. Most likely in your case the GPUs overperform the CPU.

[Micha]

Interesting, I use a dual xeon and have 32x3.1GHz running, but the GPU mode of GTX1080ti+GTX780 runs much faster. Also the hyprid mode isn't useful, only a few seconds can be saved. Looks like I should think about to buy more GPU power.