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When I switch between GPU and CPU mode in Maxwell Render directly, the basic scene changes significantly:



Left CPU/ Right GPU

Only when I switch the engine within C4D and hit render, I get the correct results.

Rendering with GPU doesn't hit a specified SL accurately, eg 12.04 instead of 12.



Slight differences in scaling or transformation it seems:

Aniki wrote: Rendering with GPU doesn't hit a specified SL accurately, eg 12.04 instead of 12.

My guess with this is that is normal. On cpu rays are processed 1 by 1 or a very little amount of them at the same time (one per thread), but on gpu you are processing thousands of rays at the same time. So it's normal that with those thousands of rays, the last processing batch have more rays that you need. But it takes the same time to process those thousands than a few hundreds. So better have a little higher SL than throwing away those rays, isn't it?

luis.hijarrubia wrote:

Aniki wrote: Rendering with GPU doesn't hit a specified SL accurately, eg 12.04 instead of 12.

My guess with this is that is normal. On cpu rays are processed 1 by 1 or a very little amount of them at the same time (one per thread), but on gpu you are processing thousands of rays at the same time. So it's normal that with those thousands of rays, the last processing batch have more rays that you need. But it takes the same time to process those thousands than a few hundreds. So better have a little higher SL than throwing away those rays, isn't it?

sure thing, just wondering how it will behave when merging different SLs in Coop etc..

Aniki wrote:

luis.hijarrubia wrote:

Aniki wrote: Rendering with GPU doesn't hit a specified SL accurately, eg 12.04 instead of 12.

My guess with this is that is normal. On cpu rays are processed 1 by 1 or a very little amount of them at the same time (one per thread), but on gpu you are processing thousands of rays at the same time. So it's normal that with those thousands of rays, the last processing batch have more rays that you need. But it takes the same time to process those thousands than a few hundreds. So better have a little higher SL than throwing away those rays, isn't it?

sure thing, just wondering how it will behave when merging different SLs in Coop etc..

Merging different SL have never been a problem. You can merge SL 6 with SL 3 or whatever.

Aniki wrote:When I switch between GPU and CPU mode in Maxwell Render directly, the basic scene changes significantly:

Only when I switch the engine within C4D and hit render, I get the correct results.

As mentioned in my reply to your other post, this is unfortunately not to be unexpected at this time. I know work was done to get around it, because I found that work ended up breaking some other cases, so it had to be rolled back.