[Bf-cycles] GSoC 2018 proposal discussion: hair shader

Leonardo E. Segovia leonardo.segovia at cs.uns.edu.ar
Tue Mar 13 22:50:15 CET 2018

Hi all,

2018-03-13 12:43 GMT-03:00 Brecht Van Lommel <brechtvanlommel at pandora.be>:
> The current hair BSDF (kernel/closure/bsdf_hair.h) is based on the Marschner
> model and this paper:
> http://graphics.pixar.com/library/ImportanceSamplingHair/. Most of the PBRT
> code would go to a new BSDF in kernel/closure, and both an SVM and OSL
> shader can then create this closure. We need both SVM and OSL shader nodes,
> but it's probably best to start with SVM and then implement the OSL shader a
> bit later in the planning, once most things are working.

Thanks for the tip. I had only looked at the OSL shader itself, that's
why I thought it was Kajiya-Kay. I'll update the relevant section.
As for the SVM/OSL stuff: initially, I couldn't find much information
about Cycles' shader architecture. Now that I know the difference,
what I could find is this post:
https://code.blender.org/2012/09/open-shading-language-in-cycles/, but
with the source code I think it's more than enough . Do you have any
more documentation about them (especially w.r.t SVM) ?

> It may be good to have a bit more detail on what you can do once the code is
> working, which I hope there will be time for since this is porting an
> existing implementation. Running a profiler is fine, but it's also important
> to look at things like sampling noise, behavior with point and area lights,
> caustics and the filter glossy option, etc. If we can get an early build
> users we can also get feedback if the parameters are intuitive or if there
> need to be some changes or additions. It's difficult to plan for this, but
> some more detail than "Testing and bug fixes" would be good.

Thanks again, I'll add more details about testing.
About debug builds: does Blender Foundation have a buildbot or Travis
instance to generate them?

Lic. Leonardo E. Segovia
Departamento de Ciencias e Ingeniería de la Computación
Universidad Nacional del Sur
San Andrés 800 - Campus Palihue, B8000 Bahía Blanca, Argentina

More information about the Bf-cycles mailing list