Unable to use the exported .obj file with torch3d for rendering

[siddhant230]

First of all thanks for such amazing work, this really is helpful.
I am trying to render the .obj file usng torch3d as per the code below, but it is asking for texture which I am not sure how to get.
While loading itself I get this warning
/usr/local/lib/python3.10/dist-packages/pytorch3d/io/obj_io.py:550: UserWarning: Mtl file does not exist: /content/data/cow_mesh/cow.mtl warnings.warn(f"Mtl file does not exist: {f}"),
hence I donwnloaded a dummy obj, mtl and texture.png file using

!wget -P data/cow_mesh https://dl.fbaipublicfiles.com/pytorch3d/data/cow_mesh/cow.obj

!wget -P data/cow_mesh https://dl.fbaipublicfiles.com/pytorch3d/data/cow_mesh/cow.mtl

!wget -P data/cow_mesh https://dl.fbaipublicfiles.com/pytorch3d/data/cow_mesh/cow_texture.png

torch3d runs flawlessly with this, but if I remove mtl it stops working completely. I am really stuck with this. My objective is to render obj from triposr from multiple angles and save the images. Is there a direct or alternate way to solve this. Also please point if I am doing something wrong. I would be really greatful. Thanks.

CODE
`
import torch
from pytorch3d.io import load_objs_as_meshes, load_obj
from pytorch3d.structures import Meshes

from pytorch3d.renderer import (
look_at_view_transform,
FoVPerspectiveCameras,
RasterizationSettings,
MeshRenderer,
MeshRasterizer,
PointLights,
SoftPhongShader
)

device = torch.device("cuda") if torch.cuda.is_available() else "cpu"

load mesh

obj_filename = "mesh.obj"
mesh = load_objs_as_meshes([obj_filename], device=device)

R, T = look_at_view_transform(2.7, 0, 180)
cameras = FoVPerspectiveCameras(device=device, R=R, T=T)

raster_settings = RasterizationSettings(
image_size=512, blur_radius=0.0, faces_per_pixel=1
)

lights = PointLights(device=device, location=[[0.0, 0.0, -3.0]])

renderer = MeshRenderer(
rasterizer=MeshRasterizer(cameras=cameras,
raster_settings=raster_settings),
shader=SoftPhongShader(device=device,
cameras=cameras,
lights=lights)
)

multi-view

bs = 5
meshes = mesh.extend(bs)

elev = torch.linspace(0, 180, bs)
azim = torch.linspace(-180, 180, bs)

R, T = look_at_view_transform(dist=2.7, elev=elev, azim=azim)
cameras = FoVPerspectiveCameras(device=device, R=R, T=T)

lights.locaion = torch.tensor([[0.0, 0.0, -3.0]], device=device)

render

images = renderer(meshes, cameras=cameras, lights=lights)

ERROR : ValueError: Meshes does not have textures

`

`
"""
ERROR:

---

ValueError Traceback (most recent call last)
in <cell line: 1>()
----> 1 images = renderer(meshes, cameras=cameras, lights=lights)

6 frames
/usr/local/lib/python3.10/dist-packages/torch/nn/modules/module.py in _wrapped_call_impl(self, *args, **kwargs)
1530 return self._compiled_call_impl(*args, **kwargs) # type: ignore[misc]
1531 else:
-> 1532 return self._call_impl(*args, **kwargs)
1533
1534 def _call_impl(self, *args, **kwargs):

/usr/local/lib/python3.10/dist-packages/torch/nn/modules/module.py in _call_impl(self, *args, **kwargs)
1539 or _global_backward_pre_hooks or _global_backward_hooks
1540 or _global_forward_hooks or _global_forward_pre_hooks):
-> 1541 return forward_call(*args, **kwargs)
1542
1543 try:

/usr/local/lib/python3.10/dist-packages/pytorch3d/renderer/mesh/renderer.py in forward(self, meshes_world, **kwargs)
62
63 fragments = self.rasterizer(meshes_world, **kwargs)
---> 64 images = self.shader(fragments, meshes_world, **kwargs)
65
66 return images

/usr/local/lib/python3.10/dist-packages/torch/nn/modules/module.py in _wrapped_call_impl(self, *args, **kwargs)
1530 return self._compiled_call_impl(*args, **kwargs) # type: ignore[misc]
1531 else:
-> 1532 return self._call_impl(*args, **kwargs)
1533
1534 def _call_impl(self, *args, **kwargs):

/usr/local/lib/python3.10/dist-packages/torch/nn/modules/module.py in _call_impl(self, *args, **kwargs)
1539 or _global_backward_pre_hooks or _global_backward_hooks
1540 or _global_forward_hooks or _global_forward_pre_hooks):
-> 1541 return forward_call(*args, **kwargs)
1542
1543 try:

/usr/local/lib/python3.10/dist-packages/pytorch3d/renderer/mesh/shader.py in forward(self, fragments, meshes, **kwargs)
126 def forward(self, fragments: Fragments, meshes: Meshes, **kwargs) -> torch.Tensor:
127 cameras = super()._get_cameras(**kwargs)
--> 128 texels = meshes.sample_textures(fragments)
129 lights = kwargs.get("lights", self.lights)
130 materials = kwargs.get("materials", self.materials)

/usr/local/lib/python3.10/dist-packages/pytorch3d/structures/meshes.py in sample_textures(self, fragments)
1546 )
1547 else:
-> 1548 raise ValueError("Meshes does not have textures")
1549
1550 def submeshes(

ValueError: Meshes does not have textures
"""
`