fix: fix the dimension comments of t_sorted and t_indices (#221)

Co-authored-by: chihaoliang(chihaoliang) <chihaoliang@tencent.com>

nerfacc/cuda/csrc/nerfacc.cpp

@@ -55,8 +55,8 @@ std::tuple<RaySegmentsSpec, RaySegmentsSpec, torch::Tensor> traverse_grids(
     const torch::Tensor binaries,  // [n_grids, resx, resy, resz]
     const torch::Tensor aabbs,     // [n_grids, 6]
     // intersections
-    const torch::Tensor t_sorted,  // [n_rays, n_grids]
-    const torch::Tensor t_indices,  // [n_rays, n_grids]
+    const torch::Tensor t_sorted,  // [n_rays, n_grids * 2]
+    const torch::Tensor t_indices,  // [n_rays, n_grids * 2]
     const torch::Tensor hits,    // [n_rays, n_grids]
     // options
     const torch::Tensor near_planes,

nerfacc/grid.py

@@ -107,8 +107,8 @@ def traverse_grids(
     over_allocate: Optional[bool] = False,
     rays_mask: Optional[Tensor] = None,  # [n_rays]
     # pre-compute intersections
-    t_sorted: Optional[Tensor] = None,  # [n_rays, n_grids]
-    t_indices: Optional[Tensor] = None,  # [n_rays, n_grids]
+    t_sorted: Optional[Tensor] = None,  # [n_rays, n_grids * 2]
+    t_indices: Optional[Tensor] = None,  # [n_rays, n_grids * 2]
     hits: Optional[Tensor] = None,  # [n_rays, n_grids]
 ) -> Tuple[RayIntervals, RaySamples, Tensor]:
     """Ray Traversal within Multiple Grids.
@@ -129,8 +129,8 @@ def traverse_grids(
         traverse_steps_limit: Optional. Maximum number of samples per ray.
         over_allocate: Optional. Whether to over-allocate the memory for the outputs.
         rays_mask: Optional. (n_rays,) Skip some rays if given.
-        t_sorted: Optional. (n_rays, n_grids) Pre-computed sorted t values for each ray-grid pair. Default to None.
-        t_indices: Optional. (n_rays, n_grids) Pre-computed sorted t indices for each ray-grid pair. Default to None.
+        t_sorted: Optional. (n_rays, n_grids * 2) Pre-computed sorted t values for each ray-grid pair. Default to None.
+        t_indices: Optional. (n_rays, n_grids * 2) Pre-computed sorted t indices for each ray-grid pair. Default to None.
         hits: Optional. (n_rays, n_grids) Pre-computed hit flags for each ray-grid pair. Default to None.
 
     Returns:
@@ -171,8 +171,8 @@ def traverse_grids(
         binaries.contiguous(),  # [m, resx, resy, resz]
         aabbs.contiguous(),  # [m, 6]
         # intersections
-        t_sorted.contiguous(),  # [n_rays, m]
-        t_indices.contiguous(),  # [n_rays, m]
+        t_sorted.contiguous(),  # [n_rays, m * 2]
+        t_indices.contiguous(),  # [n_rays, m * 2]
         hits.contiguous(),  # [n_rays, m]
         # options
         near_planes.contiguous(),  # [n_rays]