Difference in rendering time despite identical settings

Jayn25

I have two scenarios - exact same scene, exact same render settings (resolution etc), exact same environment and tonemapper settings. But one render takes 3-8 minutes, the other one 30-50 minutes. The only difference is different premade HDRI environment (so lighting color is different). But both of them are 4k.

What are the other things that I could be missing?

Richard Haseltine

The different lighting could account for the issue - high-contrast, with some areas receiving little direct light, do tend to take longer, but it also sounds as if one scene may be just squeaking into the GPU memory and the other just exceeding it - check the log file (Help>Troubleshooting>View Log file) to see if one render is going to CPU rather than GPU.

Jayn25

Richard Haseltine said:

The different lighting could account for the issue - high-contrast, with some areas receiving little direct light, do tend to take longer, but it also sounds as if one scene may be just squeaking into the GPU memory and the other just exceeding it - check the log file (Help>Troubleshooting>View Log file) to see if one render is going to CPU rather than GPU.

Scene is just a placeholder flat surface + character and GPU has 100% usage in both cases. Difference in direct light might be the case here.

PerttiA

What do the logs say (Help->Troubleshooting->View Log File)?

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TheMysteryIsThePoint

Does it matter which scene you render first after startup? I would swear I read some anecdotal discussions about IRay not clearing VRAM...

alan bard newcomer

TheMysteryIsThePoint said:

Does it matter which scene you render first after startup? I would swear I read some anecdotal discussions about IRay not clearing VRAM...

seen that enough and occasionally had to do it in the past... it's probably past anecdotal into the field of cannon.