Some scenes render in CPU even though they rendered GPU before

RLP

Some scenes I create go to CPU render even though they have rendered befor in GPU. In some cases a scene that just rendered in GPU crashes to CPU when rendering after several people have been removed from the scene. It doesn't seem to depend of the complexity or size of the rendered scene. Simple scenes go straight to CPU while scenes with four or five series 8 people on an "Iray Worlds" (lots of trees etc.) background render in GPU mode What the heck is the governing factor here. CPU mode takes hours and usually looks worse because it often does less iterations.

ebergerly

Hard to say without specifics, but If you're rendering, modifying the scene, and re-rendering without closing the scene, I *think* that Iray doesn't do a good job of clearing the resources (like VRAM) from the first render, and instead adds on with the second render. Not sure if that's still true though.

 

Kitsumo

It depends on how much system RAM and GPU VRAM you have. Four or five Gen 8 people with environment is a huge rendering task.

The first thing I would do is go to Help>Troubleshooting>View Log File, and scroll to the bottom of the log. It should show your most recent render so you can see why it dropped to CPU. It should tell you how much RAM is being use for textures and geometry and things like that. Also you can use Windows Task Manager to see how much RAM you're using, and a utility like MSI Afterburner or GPU-Z to see how much VRAM you're using. Once you have the info, then you can figure out how to solve your problem.

Visuimag

Yeah, knowing your specs would help. On top of that, if you haven't already, I'd buy this: https://www.daz3d.com/scene-optimizer

One of the best investments Iray render users can make!

RLP

Thanks. I think it's not letting loose of memory. Used to be no problem but something changed somewhere.

I'm running an eight core Ryzen with 16 Gigs of RAM and a GTX1080 plus a GTX1070 so even with a fast processor the slowdown is massive.

Saving, closing and re-opening seems to help. I'll also look into that optimizer. I used to get away with two dozen G2 characters in a scene so it seems like every upgrade in figures needs an upgrade in computer. Probably need a workstation with a pair of 12 core CPUs, 128Gigs of RAM and dual RTX2080ti cards by the time they hit genesis 10.

TheKD

DS is hit or miss when it comes to letting go of vram for some reason. Sometimes I am able to do 20 renders in a row without closing, other times I have to close every other render. Kinda annoying when the latter happens.

Scene optimizer is well worth it! I was a skeptic at first, thinking it was gonna make my renders turn into ps1 era looking crap or something, but I can't tell the difference. I usually half all the textures unless they are already 1k or under, before render, I haven't even been able to tell when getting pretty close to the peoples. I don't really do portrait closeup type renders, so not sure if it will be noticable in those closeups. I normally try to render at 3k longest side at least when I can. A few more crowded scenes I have to cut it up a bit, make a foreground and backround pass.

Paradigm

Try turning off the architectural and caustic filters if you have them on. I had an issue of my 2080TI dropping to CPU with those enabled

nicstt

Before what?

Remove whatever changed the situation that made you say 'before'.