Convergence

jmucchiello

What are the pros and cons of using convergence to determine when a render is "finished"? I normally leave it at 95% and allow that to dictate "done". 

But sometime I get a render, usually one with a lot of light splatter, that takes forever to converge, if at all.

Any tips? Best Practices?

Richard Haseltine

That means, most likely, that it is running out of time or samples before converging - the log file (Help>Troubleshooting>VIew Log File) should tell you why the render stopped. A sceen with lots of areas that rely on bounced light rather than being lit directly, or with lots of relfective surfaces, or with complex shaders that can divert the path a light ray is following are likely to cause this kind of thing so you could always have a Render Preset saved for tricky scenes, with no or higher limits on samples and time. Convergence usually works, but sometimes it will fail if there is a concentrated area of the render that is harder (eyes, for example, often do this) - in that case it may hit the threshold but because the remaining unconverged pixels are in a very limited area they are much more noticeable than they would be scattered across the image.