diff --git a/nerf/nerf_helpers.py b/nerf/nerf_helpers.py
index 4fcb372..520250c 100644
--- a/nerf/nerf_helpers.py
+++ b/nerf/nerf_helpers.py
@@ -103,9 +103,11 @@ def get_ray_bundle(
         ],
         dim=-1,
     )
-    ray_directions = torch.sum(
-        directions[..., None, :] * tform_cam2world[:3, :3], dim=-1
-    )
+    ray_directions = torch.tensordot(
+        tform_cam2world[:3, :3], 
+        directions.T, 
+        dims=([1], [0])
+    ).T
     ray_origins = tform_cam2world[:3, -1].expand(ray_directions.shape)
     return ray_origins, ray_directions