Fix svraster_cuda.meta imports for activation and octree utils

src/utils/octree_utils.py

@@ -8,7 +8,10 @@
 
 import torch
 import svraster_cuda
-from svraster_cuda.meta import MAX_NUM_LEVELS
+
+STEP_SZ_SCALE = getattr(svraster_cuda, "STEP_SZ_SCALE", 1.0)
+MAX_NUM_LEVELS = getattr(svraster_cuda, "MAX_NUM_LEVELS", 8)
+
 
 '''
 Define many low-level functions for the sparse voxels under Octree layout.