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Is there a way to make rendering in Cycles use less GPU resources? Like some console parameters for rendering engine or settings within Blender? I tried render scene with the console (no UI), following Blender wiki example, but it still eats all the GPU and makes it really hot to 70' Celsius. I don't mind if such settings increase render time from minutes to hours, that's kinda exactly what I need to put rendering task do the job over night and keep GPU usage around 50-60% and prevent overheating.

I'm using Linux.

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70 degrees is not too hot and it's completely normal for a working GPU. Something beyond 85 degrees would start getting concerning. Anyways, you may set the tile size to a low value (16 x 16 for instance) to get what you want. Here you can see a table that shows how different Tile sizes can affect rendering time when using a GPU.

However, from a more environmental perspective ( :) ) I don't recommend you doing this since you will have to leave your computer on for a much longer time to get the final rendering. In the meanwhile, your computer is using way more electricity than it would if you use the GPU efficiently by setting the tile size to a higher number (e.g. 224 x 224). Normally, a mid-range GPU uses around 200 watt-hours or less working with the highest load. When idle, it uses around 30-50 watt-hours. The rest of the hardware for your computer also use at least around 70-100 watt-hours in idle and maybe around 200-300 watt-hours when they are under descent load. Assuming that you don't do anything else overnight (8 hours) and just leave your computer on for rendering your computer will be using something around 8 x 200 = 1600 watt-hours. The number 200 represents 100 watt-hours for your [almost] idle computer and 100 watt-hours for your GPU which is not under heavy load due to small tile size. However, if you set the tile size to a higher number and the rendering takes 2 hours your computer would use something around 2 x 300 = 600 watt-hours. 300=100(everything except GPU) + 200 (the GPU under heavy load).

Note that all of these numbers are just a rough approximation and could widely vary depending on your hardware but one thing that won't change is that leaving your computer on for longer will potentially use more watt-hours than finishing your rendering faster and turning your machine off :)

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  • $\begingroup$ Does making tile size smaller make render engine load GPU less? Or it only increases render time? $\endgroup$ – Anna Nov 5 '18 at 14:13
  • $\begingroup$ @Anna It superficially makes the GPU be under less load. The reason is that the tiles are pretty small and are quickly processed. However it takes a long time to transfer the tiles to the GPU VRAM and make them ready to get processed by the GPU cores. The process of transferring the tiles is done sequentially and if the GPU cores are done with processing other stuff they have to wait until a new tile is ready to get processes. That's why the time increases. $\endgroup$ – Amir Nov 5 '18 at 14:24
  • $\begingroup$ Thanks for solution, it sure loads GPU smoothly but still after some time I hit 70-75' Celsius on GPU. I guess it's more of a hardware issue, why GPU fans wont spin faster. $\endgroup$ – Anna Nov 5 '18 at 14:38
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    $\begingroup$ @Anna The normal working GPU temperature is definitely around 80 degrees Celsius. Even going up to 90 degrees would be okay. Look at the stuff people have discussed in this link to learn more about the temperature issue. $\endgroup$ – Amir Nov 5 '18 at 14:59
  • $\begingroup$ Thanks for the link. I have idle GPU's temperature at 26-28' degrees Celsius, so it's not airflow issue. I see now it's right that no matter how heavily loaded by rendering GPU is, it would reach higher temperatures eventually and fans would stay slow until 94' (that's what sensors say in my case, haha) $\endgroup$ – Anna Nov 5 '18 at 15:12

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