Black output when rendering top down image

[Kurokabe]

With kaolin==0.16.0, when I use easy_render with the camera above the center of my mesh, and the camera looking straight down, I get a black image.

from kaolin.render.easy_render import render_mesh, default_lighting
from kaolin.io.usd import import_mesh
from kaolin.render.camera import Camera
import torch
from torchvision.transforms import ToPILImage

mesh = import_mesh("my_mesh.usd", triangulate=True, with_materials=True).to("cuda")

mesh.vertices.min(axis=0), mesh.vertices.max(axis=0)
center = (mesh.vertices.min(axis=0)[0] + mesh.vertices.max(axis=0)[0]) / 2

offset = 0.0

camera_y_position = 3.0

eye = torch.tensor([center[0], camera_y_position , center[2]], dtype=torch.float32)
at = torch.tensor([center[0] + offset, 0, center[2]], dtype=torch.float32)

lighting = default_lighting().to("cuda")
camera = Camera.from_args(
                eye=eye,
                at=at,
                up=torch.tensor([0.0, 1.0, 0.0]),
                fov=45,  
                width=512, height=512,
                device='cuda'
            )

with torch.jit.optimized_execution(False):
    with torch.no_grad():
        render = render_mesh(
                camera,
                mesh,
                lighting,
            )
        

ToPILImage()(render["render"][0].transpose(0, 2))

But if I add a slight offset, e.g. offset = 0.01 to either the X or Z coordinate, then I get a proper rendering.