How render image with some constant colors that described in OBJ-file

[attashe]

In this question was explained how render image without texture
#51

But in my case in MTL-file contain material with constatnt color and in OBJ-file described what vertex have this color

newmtl Color_003
Ns 96.078431
Ka 0.000000 0.000000 0.000000
Kd 0.666667 0.666667 0.666667
Ks 0.330000 0.330000 0.330000
Ke 0.000000 0.000000 0.000000
Ni 1.000000
d 1.000000
illum 2

usemtl Color_003
f 1/1 2/2 3/3
...
f 7/19 5/18 6/21
v 0.412338662557 0.0913135972693 0.18293131387
...
v 0.35328764703 0.107066507113 0.170653379949
vt -5.0965 1.0390
...
vt 5.0965 1.0390

Can I generate texture using commands from OBJ-file: usemtl Color_003?

[nikhilaravi]

In the load_obj function we load the Ns, Ka, Kd, Ks properties from the .mtl file. You can retrieve them from the aux tuple that is return from load_obj e.g.

verts, faces, aux = load_obj("path_to_mesh.obj")

per_face_material_idx = faces.materials_idx
material_properties = aux.material_colors

The materials_idx indexes into the material_properties. We also have a Materials class which can be used to store the materials for rendering.

Here is a full description of the outputs from load_obj: https://github.com/facebookresearch/pytorch3d/blob/master/pytorch3d/io/obj_io.py#L185-L199

The shaders in the renderer accept the Materials class as an input: https://github.com/facebookresearch/pytorch3d/blob/master/pytorch3d/renderer/mesh/shader.py#L43

[gkioxari]

@attashe hopefully the response above solved your question. Closing this. Feel free to reopen if you have further questions.

[Nan2018]

is there a concrete example somewhere?

I was able to create the Materials object from aux.material_colors. But passing it to shader causes a RuntimeError when rendering. (Same error with renderer(materials=materials)). My feeling is faces.materials_idx missing in the pipeline. As @nikhilaravi said, faces.materials_idx indexes into the material properties for each face, but I couldn't find a place to pass it to the renderer.