[x3d-public] UnlitMaterial

[Andreas Plesch]

Thanks for list. UnlitMaterial is certainly useful. I was just looking for
the features which are not covered by the current Material with no lights
since this would the rough starting point for supporting.

Andreas

On Fri, Feb 21, 2025, 7:44 AM Michalis Kamburelis <michalis.kambi at gmail.com>
wrote:

> UnlitMaterial is *similar but not exactly the same* as Material with
> all lights=off.
>
> It's a similar question with similar answers as "is UnlitMaterial like
> Material with all fields except emissieColor equal to zero". See
> https://github.com/michaliskambi/x3d-tests/wiki/Why-is-UnlitMaterial-useful
> for my reasoning. In short:
>
> - Better interaction with Appearance.texture : UnlitMaterial says that
> emissive parameter (not diffuse, as would be for Material) is
> multiplied by Appearance.texture.
>
> - Better interaction with Color / ColorRGBA : UnlitMaterial says that
> emissive parameter (not diffuse, as would be for Material) are
> replaced by per-vertex color.
>
>     (or multiplied by per-vertex color, if you use CGE extension
>
> https://github.com/michaliskambi/x3d-tests/wiki/Converting-glTF-to-X3D#per-vertex-colors
> "Color { mode  "MODULATE" ... }" ).
>
> - In UnlitMaterial, the texture that affects transparency is
> emissiveTexture, not diffuseTexture. I see you also mentioned this.
>
> Regards,
> Michalis
>
> czw., 20 lut 2025 o 23:23 Andreas Plesch via x3d-public
> <x3d-public at web3d.org> napisał(a):
> >
> > Looking at UnlitMaterial:
> >
> >
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD/Part01/components/lighting.html#LightingUnlit
> >
> > Can UnlitMaterial be thought of as Material without light contributions
> ? Eg. on_i for all lights is 0 ?
> >
> > It looks equivalent but perhaps there is a subtle difference. Yeah, one
> subtle difference appears to be that the transparency field is applied to
> diffuse.a rather than emissive.a .
> >
> > Related, the Phong lighting in the case of on_i all zero, does not seem
> to have a way to specify an alpha for emissive ? Not sure how much use
> emissive alpha has but UnlitMaterial has it.
> >
> > Thanks for any input, -Andreas
> >
> > --
> > Andreas Plesch
> > Waltham, MA 02453
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> > x3d-public at web3d.org
> > http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>
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