[Bf-viewport] Unified Principled BSDF and Eevee PBR

[Brecht Van Lommel]

If we need multiple models then I think it would be good to have them as an
enum in a single node. For tutorials, addons and our implementation it's a
lot simpler I think. We can hide/show sockets as needed, and convert
parameters between the different models automatically.

On Tue, Jun 27, 2017 at 9:52 PM, Clément FOUCAULT <foucault.clem at gmail.com>
wrote:

> I also don't quite like the fact of removing the specular workflow. But
> supporting it would add some usability issue (discussed previously but
> maybe reopened for debate). Adding a Specular Node is just a matter of
> usability / UI point of view. For now just supporting the Principled BSDF
> should cover most of the use cases.
>
> About your statements on the Metallic workflow:
>
> >There are often texture interpolation issues where a dielectric and
> metallic materials meet (https://s3.amazonaws.com/docs
> .knaldtech.com/docuwiki/light_fringe_values_close.jpg)
> This will happen with both workflow. I understand that interpolation of
> metallic values produces colored specular. In specular workflow it won't.
> The real workaround on this is to use layered material that are rendered
> separately, but this is too heavy for realtime games.
>
> >The metallic workflow is most often locked to 4% reflectivity for
> dielectrics which gives less control to experienced artists.
> False, the metallic workflow (as per Unreal Implementation) is using
> disney approach to give a specular input to tweak dielectrics specular
> values. So you can go up to 8% with default range and beyond if you want.
> Unfortunately it seems that Unity does not handle that. Still Metallic
> material inputs can be exported as Specular inputs. The other way in not
> easily doable.
>
> >Semi-conductors (Rust, Magnetite etc.) and crystalline objects (gem
> stones etc.) cannot be rendered accurately as they require a reflectivity
> of between 4-18%.
> Read previous point.
>
> > It's much easier to use incorrect values within the metalness mask when
> less experienced artists author content, which can break the workflow.
> It's equally easy to put incorrect Specular values with specular workflow
> ;) that's why they came up with the metallic one in the first place.
>
> Regards.
>
> Clément
>
> 2017-06-27 19:42 GMT+02:00 metalliandy <metalliandy666 at googlemail.com>:
>
>> Hey all,
>>
>> I wanted to pop in and mention that the Specular workflow is absolutely
>> not a legacy option within PBR game dev. It's a higher quality alternative
>> to the metalness workflow that is often used when users are not constrained
>> by memory limitations. This is why it is supported in Unity & Toolbag etc.
>>
>> https://docs.unity3d.com/Manual/StandardShaderMetallicVsSpecular.html
>>
>> The metalness workflow has some great positives ofc, but it also has some
>> serious limitations when it comes to accurately rendering materials.
>>
>> For example:
>>
>>    - There are often texture interpolation issues where a dielectric and
>>    metallic materials meet (https://s3.amazonaws.com/docs
>>    .knaldtech.com/docuwiki/light_fringe_values_close.jpg
>>    <https://s3.amazonaws.com/docs.knaldtech.com/docuwiki/light_fringe_values_close.jpg>
>>    )
>>    - The metallic workflow is most often locked to 4% reflectivity for
>>    dielectrics which gives less control to experienced artists.
>>    - Semi-conductors (Rust, Magnetite etc.) and crystalline objects (gem
>>    stones etc.) cannot be rendered accurately as they require a reflectivity
>>    of between 4-18%.
>>    - It's much easier to use incorrect values within the metalness mask
>>    when less experienced artists author content, which can break the workflow.
>>
>> As such I wouldn't recommend removing the specular workflow from Blender
>> as it would be severely limiting the usefulness of the viewport for artists
>> that do not use the metallic workflow.
>>
>> Cheers,
>>
>> -Andy
>>
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>
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