Noise level strange behavior

[mahmoudkeshta]

Hi,
I noticed something weird with noise level in corona 1.7 hotfix 4. Noise limit percent increases in sometimes i.e it reaches 3.92% then jumps to 4.32 % . is it normal ?. I feel that it is a bug also it causes long render time. I run 3ds max 2016 and windows 10 pro. I have amd ryzen 1950x 16 core processor and 64 GB ram.

[TomG]

Actually, it's more likely that the noise limit artificially dropped low at one adaptivity calculation (then returns to normal at the next evaluation). That one is a bug that we are aware of (https://corona-renderer.com/bugs/view.php?id=2811). If it artificially drops low and that is below the Noise Limit, then it will make the render stop early - so, rather than cause a long render time, what happens is it mistakenly causes a short render time (with more noise in the image than would be expected). Can avoid this in animations, where it might affect one frame and not others, by rendering to a Pass or Time limit.

[mahmoudkeshta]

Yes exactly it could cause unexpected noise in some case. So do you recommend to work with pass limit instead of noise limit for now? It is difficult to specify the accurate enough passes for each frame.

[TomG]

For animations, you could either use Pass or Time limits. Alternatively, you could render to a Noise limit, and if any frames are affected by early end to rendering, you could just re-render those individual frames (the unexpected drop in calculated noise is "random" so does not always occur even for the same frame).