docstr: Check that gradient flow is unaffected when the camera is inside the mesh
docstr_tok: ["Check","that","gradient","flow","is","unaffected","when","the","camera","is","inside","the","mesh"]
code: def test_grad(self):
      """
      Check that gradient flow is unaffected when the camera is inside the mesh
      """
      device = torch.device("cuda:0")
      mesh, verts = self.load_cube_mesh_with_texture(
          device=device, with_grad=True
      )
      raster_settings = RasterizationSettings(
          image_size=512,
          blur_radius=1e-5,
          faces_per_pixel=5,
          z_clip_value=1e-2,
          perspective_correct=True,
          bin_size=0,
      )
  
      renderer = MeshRenderer(
          rasterizer=MeshRasterizer(raster_settings=raster_settings),
          shader=SoftPhongShader(device=device),
      )
      dist = 0.4  # Camera is inside the cube
      R, T = look_at_view_transform(dist, 0, 0)
      cameras = FoVPerspectiveCameras(device=device, R=R, T=T, fov=90)
      images = renderer(mesh, cameras=cameras)
      images.sum().backward()
  
      # Check gradients exist
      self.assertIsNotNone(verts.grad)
  
imports: import unittest
  import imageio
  import numpy
  import torch
  from pytorch3d.io import save_obj
  from pytorch3d.renderer.cameras import FoVPerspectiveCameras, look_at_view_transform, PerspectiveCameras
  from pytorch3d.renderer.lighting import PointLights
  from pytorch3d.renderer.mesh import clip_faces, ClipFrustum, convert_clipped_rasterization_to_original_faces, TexturesUV
  from pytorch3d.renderer.mesh.rasterize_meshes import _RasterizeFaceVerts
  from pytorch3d.renderer.mesh.rasterizer import MeshRasterizer, RasterizationSettings
  from pytorch3d.renderer.mesh.renderer import MeshRenderer
  from pytorch3d.renderer.mesh.shader import SoftPhongShader
  from pytorch3d.renderer.mesh.textures import TexturesVertex
  from pytorch3d.structures.meshes import Meshes
  from pytorch3d.utils import torus
  from .common_testing import get_tests_dir, load_rgb_image, TestCaseMixin
label_desc: Use image node_id 4 for calling the TestRenderMeshesClipping obj's underlying member method code with example usage: obj.test_grad() without return types