[Bf-cycles] Volumetric patch update (now with new shiny bidirectional integrator)

[Matthew Heimlich]

Very cool stuff Storm, but without context it's kind of hard to follow
what is/isn't working in the current condition of the patch. Do you
think you could do another post to the mailing list with a simple list
like:

Volumes:

This works:
1. ...
2. ...
3. ...
etc.

This doesn't work:
1. ...
2. ...
3. ...
etc.

BiDirectional:

This works:

This doesn't work:


I think it would be very helpful for sorting out the status of your progression.

And congrats on crushing an old, annoying bug!

Thanks, keep up the good work,

Matt Heimlich

On Wed, Mar 13, 2013 at 9:10 PM, storm <kartochka22 at yandex.ru> wrote:
> It Working !1!1111
>
> Fixed very stupid off-by-one array index offset in backward pdf
> calculation. I must admit, that bug tortured me more then 6 months if
> not longer. The problem it affect only paths with 2 and more bounces,
> and as energy usually lower it was barely noticeable on test scenes, and
> i have plenty of theories why sometime color bleeding too bright,
> blaming everything, from compiler optimizer up to FPU flaw. Now that
> nightmare over and my mind got a chance to stay clear.
>
> Many scenes converging so fast i cannot believe it possible (comparing
> to my old patch ofcourse, not other renderers) that bidirectional MIS is
> really cool stuff when it work (selected hard areas close to light
> covered by complex geometry).
>
> Also, i found that current algorithm that trying to track volime media
> material from light to camera direction is horrible, must to replace it
> by something different, so light sources inside object with volume media
> rendering wrong.
>
> Another bug is related to skin-like shaders, when "mix" or "add" used to
> combine other BSDF, then volume density get wrong values (i am think
> that random values used to mix clash with value used for distance or
> maybe other reason, but fact it completely broken), so only simple like
> single glass or transparent work.
>
> MLT replaced to more interactive approach, now you can set mutations to
> insane 25000 and get cool splashy useless pictures. But it force to
> single thread model as i do not want to hack deeper in Cycles and
> rewrite parts before kernel_integrate() call. I very doubt some one even
> test it, but must note that change.
>
> Other known bugs are same as previous patches, only preview window if
> light tracing enabled (segfault otherwise), only perspective camera w/o
> DoF, only flat triangles guarantee quality if bidirectional used, only
> zero size point and emission meshes as light sources (done sime initial
> support of spot lights, but it unfinished untested and buggy), no GPU,
> no OSL, no ray visibility flags respected for light->camera rays.
>
> Adjoint BSDF is next big target, as w/o it any surface with interpolated
> normals will have ugly errors, like flat with some weird gradients. In
> addition, I think that it is reason that bump not work for light->camera
> rays. No smooth surfaces, no bump maps -> unusable for wide testing.
>
> Short plan: get rid of stupid XXX_compensation constants and other debug
> leftowers, make code close to Blender coding style.
>
> _______________________________________________
> Bf-cycles mailing list
> Bf-cycles at blender.org
> http://lists.blender.org/mailman/listinfo/bf-cycles
>