[Bf-cycles] No Caustics Feature

[Brecht Van Lommel]

On Tue, Jan 15, 2013 at 4:10 PM, Nate Wiebe <natewiebe13 at gmail.com> wrote:
> After watching this video by Sebastian (http://youtu.be/4-yCJlcXjOg), I'm
> wondering if it's possible to have this happen in the background
> automatically when enabling 'No Caustics'.
>
> It seems to me that the purpose of No Caustics isn't to remove GI or bounce
> lighting. It would be a pain to have to manage two sets of materials if you
> want to render a scene sometimes with and sometimes without caustics during
> an animation.

The option No Caustics should keep doing what it does, similar to
other render engines were you can also just disable caustics without
the render engine trying to add in a replacement. It is the intention
of this option to remove a light path.

> If it doesn't become the default action, it would be great to have an option
> somewhere to make this happen without having to change the materials. It
> greatly improves the scene without adding in the overhead of caustics.
>
> If there is a reason this could not work properly, I'd like to hear.

Well, the Filter Glossy option is intended exactly for this, however
perhaps it's not working as well as it could. Currently higher values
here will increase the roughness in Glossy BSDF's, but more roughness
doesn't quite make it diffuse, and diffuse tends to give less noise.
Perhaps we should improve this option so that the surfaces gradually
become diffuse. In fact for some BSDF's this would happen
automatically but it's not the case for the ones we implement.

Also, the trick in the video works ok for the diffuse-glossy case but
it only solves part of the problem. A rough glossy reflection followed
by a sharp glossy relection will still show the same noise, the Filter
Glossy option was intended to handle both cases. So I think it would
be better to look into improvements there.

Brecht.