Trimesh GLTF export how to set pbr material

[SimonScholl]

Hello community, i have a Trimesh object
trimesh_mesh = trimesh.Trimesh(vertices=vertices, faces=faces, vertex_normals=vertex_normals, validate=True)
Which i export as gltf

trimesh_scene = trimesh.Scene(geometry=trimesh_mesh)
    with open(gltf_path, 'wb') as f:
        f.write(trimesh.exchange.gltf.export_glb(trimesh_scene, include_normals=True))

My question, how can i apply a custom pbr material to the trimesh_mesh before exporting? My first attempt was to define a json

 new_material = {
        'pbrMetallicRoughness': {
            'baseColorFactor': [ 0.5, 0.8, 0.0, 1.0 ],           
            'metallicFactor': 0,
            'roughnessFactor': 0,
        }
    }

And add it like
trimesh_mesh.visual.material = new_material

But that changes nothing to the default material.

[mikedh]

Hey, unfortunately the GLTF exporter doesn't support texture at the moment, although it is on the list of requested features (#199). PR's welcome!

[mikedh]

Hey, I merged GLTF texture exports in #528, now you just need to make sure that trimesh.visual is set up as PBR then that data should be preserved on export:

In [1]: import trimesh

In [2]: m = trimesh.creation.uv_sphere()

In [3]: m
Out[3]: <trimesh.base.Trimesh at 0x7f183475ff28>

In [4]: m.visual
Out[4]: <trimesh.visual.color.ColorVisuals at 0x7f183475f198>

In [5]: m.visual = trimesh.visual.TextureVisuals(material=trimesh.visual.material.PBRMaterial())

In [6]: m.visual
Out[6]: <trimesh.visual.texture.TextureVisuals at 0x7f183468d198>

In [7]: m.visual.material
Out[7]: <trimesh.visual.material.PBRMaterial at 0x7f183468d470>

In [8]: dir(m.visual.material)
Out[8]: 
['__class__',
 '__delattr__',
 '__dict__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattribute__',
 '__gt__',
 '__hash__',
 '__init__',
 '__init_subclass__',
 '__le__',
 '__lt__',
 '__module__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__setattr__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 '__weakref__',
 'alphaCutoff',
 'baseColorFactor',
 'baseColorTexture',
 'doubleSided',
 'emissiveFactor',
 'emissiveTexture',
 'main_color',
 'metallicFactor',
 'metallicRoughnessTexture',
 'normalTexture',
 'occlusionTexture',
 'roughnessFactor',
 'to_color']

In [11]: m.visual.material.baseColorFactor = [0,0,255,255]

In [12]: m.show()
Out[12]: SceneViewer(width=900, height=675)

In [13]: m.export(file_obj='blue_sphere.glb')

[legel]

This is a great implementation, very useful, thank you.

Is there any support possible for adding specular textures as well, according to the new glTF 2.0 extension?
https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_materials_specular