[Bf-cycles] Disney BRDF Implementation in Cycles

Zauber Paracelsus zauber at gridmail.org
Wed May 11 19:39:59 CEST 2016


Pardon my asking, but what is clearcloat?  Is that a simulation of 
having a thin layer of glossy/transmissive material on top of another?  
(eg: simulating things like varnish)

On 05/11/2016 01:36 PM, "Pascal Schön" wrote:
> Thanks for your quick replies.
>
> Some words to the implementation:
>
> I've already splitted the BRDF into three closures after trying to get 
> a single closure implementation to work correctly. But it came to my 
> mind that this would be against the cycles architecture of splitting 
> stuff into diffuse and glossy. And it made it also much more complex.
>
> The three closures are:
> - disney_diffuse(...): Calculates the Burley diffuse term, subsurface 
> scattering and the sheen
> - disney_specular(...): Calculates the "normal" specular highlight and 
> the metalness (also anisotropy is included here)
> - disney_clearcoar(...): By this the clearcoat specular highlight is 
> calculated (less bright and no anisotropy)
>
> In an OSL script, which is also the script for the node, these three 
> closures are called correctly and added together.
>
> I've already seen the updated version of the Disney BRDF but I wanted 
> to focus on the more simple one that was proposed in 2012. The 
> additionals (like getting from a BRDF to a BSDF) would be one of the 
> next steps.
>
> I'm going to commit my implementation to a new branch next week, 
> because this week is a bit stressful and as it is my first commit, I 
> wanted to take some time for it.
>
> Pascal
> On 11.05.16, 19:06 Stefan Werner <swerner at smithmicro.com> wrote:
>
>     Eventually, it might be interesting to split it into separate
>     closures, so that one can still use separate ray counts for
>     specular/diffuse/transmission and get them to render into separate
>     passes. This will probably require to put fresnel back into the
>     closures (going back in history, it looks like Cycles initially
>     had that).
>
>     Stefan Werner | Senior Software Engineer; Productivity & Graphics
>     Smith Micro Software, Inc. |http://www.smithmicro.com
>     <http://www.smithmicro.com> <http://www.smithmicro.com/>
>
>
>
>
>
>     On 5/11/16, 4:18 PM, "bf-cycles-bounces at blender.org on behalf of
>     Lukas Stockner" <bf-cycles-bounces at blender.org on behalf of
>     lukas.stockner at freenet.de> wrote:
>
>     >Hi!
>     >
>     >The Disney BRDF shader is actually pretty interesting for Cycles!
>     >I've played around with it for a while as well, but my code isn't
>     fully
>     >working yet, so it'd be awesome to have your code around.
>     >
>     >Some notes:
>     >- There's actually a later revision of the paper you linked with
>     a few
>     >more details, might be handy:
>     >https://disney-animation.s3.amazonaws.com/uploads/production/publication_asset/48/asset/s2012_pbs_disney_brdf_notes_v3.pdf
>     >- There's also a completely revised BSDF that includes actual
>     subsurface
>     >scattering and transmission, and they note that it solves a few
>     issues
>     >with energy conservation and path tracing in general that the
>     original
>     >2012 BRDF has:
>     >http://blog.selfshadow.com/publications/s2015-shading-course/burley/s2015_pbs_disney_bsdf_notes.pdf
>     >- I'm currently working on energy-conserving microfacet closures,
>     which
>     >would pretty much solve the issue that caused them to include the
>     sheen
>     >stuff - at the cost of not being 100% compatible to other
>     implementations.
>     >
>     >But that can all be handled later - in general, it would be
>     awesome to
>     >have the Disney BRDF/BSDF in Cycles, and your code would certainly be
>     >welcome! Even if we go with the revised BSDF, it is pretty similar to
>     >the original BRDF, so it could be upgraded easily.
>     >
>     >Lukas
>     >
>     >
>     >Am 11.05.2016 um 15:57 schrieb "Pascal Schön":
>     >> Hey guys,
>     >>
>     >> For a few months now I’m implementing (on a private repository) the
>     >> Disney BRDF shader
>     >>
>     (https://disney-animation.s3.amazonaws.com/library/s2012_pbs_disney_brdf_notes_v2.pdf)
>     >> as a new node in Cycles. By now there have only been a few external
>     >> approaches, where a render server (like in Appleseed or
>     Renderman) is
>     >> accessed by a Blender plugin. But it would be nice to get
>     access to this
>     >> without any additional software to install.
>     >>
>     >> The current state of my implementation is, that the OSL closure is
>     >> finished and has also been tested against Renderman. Both acted
>     the same
>     >> in my testcases (except for the rendering approches by the two
>     >> renderers, which cause some minor differences in indirect
>     lighting).
>     >> Another step that I’ve taken was to implement the node to
>     easily access
>     >> the Disney BRDF.
>     >>
>     >> Currently OSL has to be activated, because I haven’t done all
>     steps to
>     >> include the Disney BRDF completely in Cycles. But I think
>     that’s only
>     >> one small step to take. There I hope to get some help by the
>     community
>     >> because it's a bit confusing where to add which code fragment.
>     >>
>     >> You can see some screenshots here:
>     >>https://www.dropbox.com/sh/j7w4v0bu9a5jhvz/AADSF3nm3LZCZnHgyPMwhrT6a?dl=0
>     >>
>     >> I would be pleased if you tell me if this would be nice to have
>     or if it
>     >> is too special for Blender.
>     >>
>     >> Pascal
>     >>
>     >>
>     >>
>     >>
>     >>
>     >>
>     >>
>     >> _______________________________________________
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>     >>
>     >
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