Two-pass improves image quality with ambient cache

Hi all,
I have experienced that calculating the same image (same resolution) two times with the ambient cache one gets smoother results.

I know about ‘overture’ calculation but this might be different (?)

Thank you for your help.

That is overture calculation. Radiance is able to interpolate between ambient values that are already in the cache, resulting in a smoother image.

The advantage to rendering the first (“overture”) pass at a smaller resolution is that it takes less time, as the goal of the first pass is only to populate the ambient cache, and not to render the details.