Allow saving OBJ files with UVs without the requirement of having passed in texture_map

[foshyjoshy]

Allow saving OBJ files with UVs without the requirement of having passed in texture_map in pytorch3d/io/obj_io.py. The current code ties UV saving to texture/material writing. It should be possible to write UVs without this texture map requirement.

Thanks.

[bottler]

It is possible, both via save_obj and via the pluggable interface to save a mesh (verts and faces) to OBJ without texture data. What are you trying to do specifically? What error do you get?

[foshyjoshy]

I don't get an error. if i don't pass the texture map, it skips writing the uvs in save_obj.

This is the line that tells _save not to write the uvs.

pytorch3d/pytorch3d/io/obj_io.py

Line 755 in dd06870

save_texture = all(t is not None for t in [faces_uvs, verts_uvs, texture_map])

Here is where the writing in skipped.

pytorch3d/pytorch3d/io/obj_io.py

Line 849 in dd06870

if save_texture:

[bottler]

Oh I see. Yes, I think PyTorch3D usually doesn't consider TexturesUV data without the map being provided. Why would this be needed / wanted?

[foshyjoshy]

Im loading a obj textured mesh into pytorch3d for optimizing. For each iteration (1_000) i export the resulting meshes object as a obj into a obj sequence. /dir/object_seq.#.obj. it starts to get messy when i start saving a mtl and png per iteration. For validation/review, im loading these iteration objs into Maya where i already have set up a shader. For this setup the mtl and png are not needed.

Im working with 4k RGB textures, so writing +1_000 identical png's is not ideal for storage.

[bottler]

It sounds like quite an idiosyncratic requirement. You can send a PR if you want, but maybe you can just modify a copy of the code locally for yourself?

[foshyjoshy]

Im happy to get around this. Thought others could benefit in having this in.