I am a long-time Blender user, but have, so far, mainly worked in design and advertising. Which means, I never really felt the need to use a non-biased renderer.
For a current project, however, I need to compute a physically correct simulation of light dispersion in a prism. I chose LuxRender for this task and have been pretty happy so far with the result. However, it seems LuxRender has some hidden (read: unknown to me ;)) mechanism for deciding when to stop rendering, which means the final render never gets cleared as much as I would need it. To illustrate this, here’s the result of a five-hour render:
I do realize that fireflies are to be expected. But I’d be happy to allow LuxRender to render a few hours longer - render time is not a problem. Alas, it automatically stopped after about five hours and I don’t know why. here’s the settings that I’m using:
I have in the meantime done a few more tests and it seems, LuxRender always stops rendering after some time. Could there be some kind of criterion that checks the progress (maybe in terms of noise or brightness or something like that) and tells LuxRender to stop, as soon as it thinks that no more progress is possible?
Anyway, here’s a much simpler scene file. LuxRender also stops this after a few hours, when the scene is still quite noisy.
Thank you very much! Yes, it seems that’s what causing my problem. Will try that now.
I thought, noise-aware sampling was just helping to focus the render process on the more noisy areas. So, this also defines a stop criterion? Is this by design?
As to how many samples I’m after… actually, I’m not sure. So far I have only ever used biased renderers. For these I would probably try around 500 to 1000 samples first and increase the number, if the scene doesn’t clear up. Can these numbers be compared to LuxRender?
Noise aware does that, but when a limit is reached… then the machine, as it has fulfilled it’s task, stops.
About samples, in technical sense, number of samples per pixels are just that… in every engine. It is not the quality level of a render per se, which depends on many facts, especially lighting & materials, shaders in use.
i.e. the subsurface shading needs a lot more samples to result in a clean image than the diffuse alone.
It is that Lux is far more complex, a different beast, in my experience (&knowledge) with still imagery surpassing even the physically correct M~R… but that’s another topic
Anyways you can always continue rendering where you left off: How Do I Continue a Render Later? and a forum post: Stop and Resume Later…
… enjoy.
Thanks, that’s good to know. And I will definitely make use of the possibility to resume a render.
Yeah, I was just thinking that using a non-biased renderer would probably mean that a higher number of samples would be necessary (less optimizations, less heuristics…).
Anyway, thank you very much for your help. You saved me a lot of headache.
Can you share your scene file?
Yes, it seems that’s what causing my problem. Will try that now.