When I render out zdepth passes I normally zoom right into an area of the picture where there's a good amount of contrast between pixels, and then let it render until the pixels visibly stop changing.
Would it be possible to have corona automatically do this check during rendering and then stop once the number of pixels changing has dropped below a user set %....for example if its a 100px by 100px image and the user sets "stop at active pixels" to 5%, then the render would stop once less than 50 pixels are changing value per pass.
It would take the guess work out of specifying how long or how many passes are needed. Perhaps it would also be possible to then calculate from this data how many passes would be needed for larger resolution final renders when sending off to a render farm for example.
