Techniques to stay off the CPU when rendering

RenderNovice

Daz's documentation/tutorials tell us the file you're about render must "fit" within your GPU'S memory capacity -- or the job gets pushed to your CPU, with a massive hit in rendering speed. Hence, they're currently recommending an NVIDIA card w at least 4GB of memory. I have apps to tell me which processor has been "given" the rendering job whenever I start a render -- and I've seen two identical render attempts go to the GPU on one attempt, then the CPU on the next. Hmmmm... Lots of characters in your scene reportedly drives up the memory demands -- to the point you get pushed to the CPU. But why the variability during multiple render attempts of identical scenes? Some here are recommending a cache - clear (F2) immediately beforehand. Others are recommending selecting both the GPU and CPU for rendering under the advanced rendering settings tab -- which seems contrary to Daz's guidance. Any insight on these two issues, anyone? Finally: what if I were to delete those characters, scene elements,(walls, ceilings, etc) props, etc that do NOT appear within the viewport for a specific render attempt? Wouldn't that reduce the overall size of the file, allowing one to more easily remain within your graphic card's memory limits? This seems somewhat intuitive to me, but Daz's "Faster Rendering" tutorial says nothing of it. Any insight here would also be appreciated!

Richard Haseltine

Make sure you are closing the open render window between attempts, as it reserves memory while open (so that it can be resumed). Even if you do close the window, there may be some increase in memory use or memory may be fragmented leading to marginal scenes failing to fit on a second attempt.

Yes, removing (or hiding) elements will stop them from using memory, though it maya ffect the lighting of your scene.

Richard Haseltine

Make sure you are closing the open render window between attempts, as it reserves memory while open (so that it can be resumed). Even if you do close the window, there may be some increase in memory use or memory may be fragmented leading to marginal scenes failing to fit on a second attempt.

Yes, removing (or hiding) elements will stop them from using memory, though it maya ffect the lighting of your scene.

RenderNovice

Thankyou, Richard!

I have indeed seen that closing/re-launching DAZ and/or rebooting seems to lead to more GPU-processed jobs -- but its a pain.  GREAT tip on closing partially-rendered windows!  I hadn't thought about the impact on lighting by deleting/hiding scene elements.  So I might leave walls/ceilings alone -- but hide other characters/props not in the viewport field-of-view.

Any thoughts on selecting BOTH the CPU and GPU when rendering?   

kaotkbliss

Instance any objects that are repeated in your scene (trees, rocks, books, ect.) and under the optimization tab for render settings choose memory instead of speed.

reduce texture sizes where you can. Replacing textures with shaders might help too.

I think that's about all I have for now.

Richard Haseltine

I think people have had mixed experience with running both CPU and GPU - it probably depends on how the loads balance. Try some tests and see how it goes - it won't do any actual harm.

RenderNovice

Thanks to you both! Great thoughts/techniques and will be experimenting w all!

artinstead_8519dc488a

Okay, enlightening. I always figured that it was only the items in the viewport that determined how fast/slow the render time. My PC was hanging to the point of me doing a hard reset out of frustration on certain detailed models but I was only rendering maybe a person's face. Based on this info I proceeded to hide everything that didn't compromise the scene and the render was fine.