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Texture baking multiple objects to one texture using Cycles with OptiX. The CPU usage is mostly 100%, and GPU 0% apart from the times when an object is finished baking, and as the next one begins the process, the CPU usage falls down to 10-20%, and GPU goes up to 80% for a moment, until falling back down again, and CPU skyrockets once more. My GPU: NVIDIA GeForce RTX 4070 12gb VRam CPU: AMD Ryzen 7-5800X 8 Core enter image description here

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Device is set to GPU Compute. Unsure if it's supposed to be like this or not, so I'd rather ask fully.

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  • $\begingroup$ I've watched a tutorial on Youtube which says you have to uncheck your CPU (as you did) and do not use OptiX but use CUDA instead. But the video is 3 years old. I cannot verify this at the moment because my PC here has an old GPU which is not very fast anyway. But no matter which I choose, as long as the GPU is checked in the preferences, the GPU shows it's being used in the performance monitor. $\endgroup$ Sep 18, 2023 at 7:03

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I made some comparisons, but I only have an old AMD Ryzen 7 2700X OctaCore CPU with an old GTX 1060 6GB GPU. Generally speaking, using the GPU was always faster than just CPU (of course), and GPU alone was faster than GPU + CPU with CUDA generally faster than OptiX, whereas OptiX with CPU was faster than without. As I said, this could all be dependent on my hardware.

But in all cases Blender was using the GPU when it was enabled. However, there was one discovery that I made: Your performance monitor shows "3D" on the first diagram. I had to switch it to "Cuda" - no matter if Blender was set to CUDA or OptiX - to see the full working load.

This is not a real solution if your GPU actually is not being used, but I simply cannot recreate this issue. As I said, if I switch the diagram to "Cuda", I can see it working in the performance monitor as long as I'm not switching to CPU. Have you switched to CPU intentionally to check against the baking performance with GPU? Is the baking time the same/similar? If not, your Blender will most likely use the GPU.

Another thing which will only use the CPU and always comes between switching from one object to the next is the Denoise for Render. If you have it enabled, after rendering with the GPU, the CPU will take over to denoise the baked image.

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  • $\begingroup$ I do have denoise on, yup, will check how things go without when able to; thanks for the suggestions. $\endgroup$
    – hunhow
    Sep 18, 2023 at 20:08

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