Rendering converged ratio: why does this happen?

Jumbotron

Hello,

In one render I made recently, it took the application over 10,000 iterations to reach the 90 % converged ratio mark. I rendered to a beauty canvas without Alpha. Then I realized that I was not happy with the look of the hair of one model appearing in the render. After I made the necessary adjustments on the hair, I enabled the Alpha on the beauty canvas and spot rendered the head of this model in order to overlay the Alpha canvas later in the postwork stage. My surprise came when I noticed that now for this spot render of the model's head, it took the application around 35,000 iterations to hit the 90% converged ratio mark. Why this discrepancy? Any ideas? Thanks.

DrunkMonkeyProductions

The short version, the spot render was more complex than the full render, mathematically speaking.

Itterations are the number of times the render is refined.

Convergence ratio is the point at which x% of pixels are considered 'converged' and are no longer being refined.

 

In general i recommend not worrying about these numbers, as they're not an indication of a render being complete, but are just a point at which the render is stopped automatically.

if you turn off render quality(before you push the render button, as you can't disable it once the render is started), set max samples and time to -1, it will effectively render forever.

Jumbotron

I see. Thanks, DrunkMonkeyProductions. :)