Print a warning message when importing a glTF file that references a specular/glossiness map

[Calinou]

See also godotengine/godot#42235.

Describe the project you are working on:

The Godot editor 🙂

Describe the problem or limitation you are having in your project:

Godot doesn't print a warning message when importing a specular/glossiness map from a glTF file. However, Godot does not support the specular/glossiness PBR workflow. It only supports the roughness/metallic workflow in the interest of simplicity and consistency.

An alternative would be to convert the specular/glossiness maps to roughness/metallic maps automatically when importing the textures. This sounds difficult to do in an accurate manner, though. Is there any literature on this?

Describe the feature / enhancement and how it helps to overcome the problem or limitation:

The glTF importer should print a warning message when importing a glTF file that either contains or references specular or glossiness maps.

Describe how your proposal will work, with code, pseudocode, mockups, and/or diagrams:

The warning message could be something along those lines:

The glTF file "<full path>" contains a <specular/glossiness> map, but Godot only supports the roughness/metallic PBR workflow. Please convert the specular/glossiness maps to roughness/metallic maps and re-export the glTF file with the new textures referenced.

If this enhancement will not be used often, can it be worked around with a few lines of script?:

No, as this is core import functionality. This is also about improving new users' experience with Godot.

Is there a reason why this should be core and not an add-on in the asset library?:

This is core import functionality.

[fire]

For reference: godotengine/godot#38796

Convert the specular/glossiness maps to roughness/metallic maps automatically