[Bf-cycles] Base 'Render' samples (simple request)

[Brecht Van Lommel]

Hi,

What you're proposing here are basically the first steps to an
adaptive sampling algorithm. I think that would be great to add, but
implementing this well is not so easy. Which is not to say that I
don't think it shouldn't be done, but that it's going to take more
than a few days of work to have this working really well.

I'm not sure if you're proposing this for per pixel adaptive sampling,
or deciding to stop for the entire frame. In the latter case this is a
bit problematic, since using the mean value may still mean there is a
lot of noise in part of the image, and the min/max may lead to one bad
pixel holding back the entire image. So this should really be done on
a per pixel level.

The difference image you show looks like it shows the noise in the
image, but this is deceiving, it only shows part of the pixels that
actually have noise. If you're going to make a decision, this pixel
needs no more samples, you have to do that with great confidence. If
you're wrong 5% or even 1% of the time, that's still many pixels that
will be wrong.

There's a few ways to improve this, among them using information from
neighbouring pixels (blurring the difference image) and using more
statistical measures. Tweaking and testing this all takes time :)

Brecht.

On Sun, Nov 13, 2011 at 2:02 AM, Jordan Miller <jrdnmlr at gmail.com> wrote:
> I've added more details here:
> http://wiki.blender.org/index.php/Dev:2.6/Source/Render/Cycles/ReducingNoise
>
> thoughts?
>
> jordan