[x3d-public] UnlitMaterial

[Michalis Kamburelis]

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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