How Is This Scene Being GPU Rendered? Post Denoiser?

AlexBarclay

So I've been researching these forums for a long time, and one thing I keep reading is that if you have an 8GB card like I do (GTX 1070), a scene that is around 18GB won't fit into the video card's memory, and therefore it will be rendered by the CPU.

My experience has reflected this, until I turned on all the "Post Denoiser" options in Iray.

Once the render gets to the iteration I specify in "Post Denoiser Start Iteration" (50), the whole scene becomes less grainy and, above all, the GPU is now showing 98% activity.

The screenshot below was taken right when the GPU activity spiked and the Denoiser appears to have kicked in.

Render times were also cut from around 30 minutes down to 10 minutes.

My question is, how is the GPU getting involved when the scene is larger than 8gb? And why only when I enable the Denoiser in render settings?

kenshaw011267

How do you know that simple scene uses 18Gb of VRAM? The amount of RAM in use is not the same. The denoiser only works when the render is running on the GPU so it certainly looks like it is and even a 30 minute render of that scene is way too fast for a CPU render, also a CPU render would have the CPU fully loaded throughout the render not the 30% or so your image shows. I'd guess the scene is somewhere around 6.5 Gb based on the VRAM usage on the GPU. To see for yourself that the GPU is doing the rendering open Task Manager->Performance->GPU select one of the graphs and click the down arrow by the title, teh dropdown that appears should include CUDA, select it. If the graph shows a lot of activity the the GPU is rendering.