[x3d-public] X3D Agenda 19 June 2020: Mantis issues

Michalis Kamburelis michalis.kambi at gmail.com
Fri Jun 19 07:55:31 PDT 2020


As for PBR notes:

pt., 19 cze 2020 o 16:37 GPU Group <gpugroup at gmail.com> napisał(a):

> 1269            glTF physically based rendering PBR, advanced material
> textures and lighting
>
> - freewrl implemented except EnvironmentLight. and direct gltf loading
>
> - freewrl: no objection to EnvironmentLight - (freewrl needs work)
>
>
>
> related: MultiTexture conundrum not solved:
>
> --Lighting model implies texture is an input to lighting so comes first,
>
> -- Multitexture implies Lighting comes first, so REPLACE can replace
>
> pre-PBR technique: put (1,1,1,1) as placeholder for texture, in Lighting,
> and modulate output diffuse component with Multitexture
>
> post-PBR method: Physical lighting doesn't have compoentents, so can't
> post-modulate to solve conundrum
>
> Options:
>
> 1) Multitexture's a priori Lighting would be Gouraud / vertex shader
> lighting, multitexture applied before Phong/frag lighting
>
> 2) Multitexture not applied to Physical
>
>
My PR contains a prose how to deal with MultiTexture . It should work in
all lighting models (Material, PhysicalMaterial, UnlitMaterial) in a way
that is also backward-compatible.

My PR will also contain (I have it written locally, not yet in the spec)
what to do when browser wants to use Gouraud shading. This decision is
independent from the lighting model. As in X3D 3, you can use Gouraud
shading or Phong shading with Phong lighting model (Material node) or
others. The lighting equations (in X3D 3 already) actually require using
Phong shading (since they say that texture should only affect diffuse), but
I want to recognize that most (all?) X3D browsers, including FreeWRL and
view3dscene, enable both Gouraud shading and Phong shading, and add
clarification how to deal with Gouraud shading to the spec.

Regards,
Michalis
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