fix broken example code

README.md

@@ -21,6 +21,7 @@ pip install .
 ```
 ## 📖️ Example
 ```python
+import torch
 import trimesh
 import matplotlib.pyplot as plt
 from triro.ray.ray_optix import RayMeshIntersector
@@ -30,14 +31,14 @@ mesh = trimesh.creation.icosphere()
 intersector = RayMeshIntersector(mesh)
 
 # generating rays
-x, y = torch.meshgrid([torch.linspace([-1, 1, 800]), 
-                       torch.linspace([-1, 1, 800])], indexing='ij')
+y, x = torch.meshgrid([torch.linspace(1, -1, 800), 
+                       torch.linspace(-1, 1, 800)], indexing='ij')
 z = -torch.ones_like(x)
-ray_directions = torch.cat([x, y, z], dim=-1).cuda()
+ray_directions = torch.stack([x, y, z], dim=-1).cuda()
 ray_origins = torch.Tensor([0, 0, 3]).cuda().broadcast_to(ray_directions.shape)
 
 # OptiX, Launch!
-hit, front, ray_idx, tri_idx, location, uv = sr.intersects_closest(
+hit, front, ray_idx, tri_idx, location, uv = intersector.intersects_closest(
     ray_origins, ray_directions, stream_compaction=True
 )