pbrt --upgrade needs support for the Disney material

[mmp]

pbrt-v4 no longer includes the Disney material, but pbrt --upgrade doesn't do anything with it. We should try to do some sort of reasonable mapping to the new material models.

[howetuft]

Hello @mmp,

First, thank you for this new version of your great and inspiring rendering engine!

I'd like to write an exporter from FreeCAD to pbrt-v4, but for this purpose I need to export Disney material somehow.

--> Have you eventually described the mapping from v3 Disney to v4 new material models?

(Please note that, if I dare, I would ask you to reintroduce Disney shader, in v4. It is a very convenient shader, even though not very academic)

Thanks!

[mmp]

Have you eventually described the mapping from v3 Disney to v4 new material models?

Not yet. Patches welcome. :-)