fix: Auto-detect SH degree for Isaac Sim NuRec compatibility

threedgrut/export/scripts/ply_to_usd.py

@@ -84,7 +84,7 @@ def main():
         conf = load_default_config()
         model = MixtureOfGaussians(conf)
 
-        # 2. Use init_from_ply
+        # 2. Use init_from_ply (now with built-in SH auto-detection for Isaac Sim compatibility)
         logger.info(f"Loading PLY with init_from_ply: {input_path}")
         model.init_from_ply(str(input_path), init_model=False)
 

threedgrut/export/usdz_exporter.py

@@ -77,6 +77,20 @@ def export(self, model: ExportableModel, output_path: Path,
                 logger.warning(f"Failed to apply normalizing transform: {e}")
                 normalizing_transform = np.eye(4)
 
+        # Auto-detect SH configuration for Isaac Sim compatibility
+        # Ensure radiance_sph_degree matches n_active_features to avoid performance issues
+        effective_radiance_sph_degree = conf.render.particle_radiance_sph_degree
+        if n_active_features == 0:
+            # DC-only case: force radiance_sph_degree to 0 for Isaac Sim performance
+            effective_radiance_sph_degree = 0
+            logger.info("Isaac Sim compatibility: setting radiance_sph_degree=0 for DC-only data")
+        elif n_active_features != conf.render.particle_radiance_sph_degree:
+            # SH degree mismatch: use the actual features available
+            effective_radiance_sph_degree = n_active_features
+            logger.info(f"Isaac Sim compatibility: adjusting radiance_sph_degree from {conf.render.particle_radiance_sph_degree} to {n_active_features}")
+        else:
+            logger.info(f"Using configured radiance_sph_degree={effective_radiance_sph_degree}")
+
         # Set up common parameters
         template_params = {
             "positions": positions,
@@ -93,7 +107,7 @@ def export(self, model: ExportableModel, output_path: Path,
             "rotation_activation": "normalize",  # Always normalize for rotations
             "density_kernel_density_clamping": conf.render.particle_kernel_density_clamping,
             "density_kernel_min_response": conf.render.particle_kernel_min_response,
-            "radiance_sph_degree": conf.render.particle_radiance_sph_degree,
+            "radiance_sph_degree": effective_radiance_sph_degree,
             "transmittance_threshold": conf.render.min_transmittance,
         }
 

threedgrut/model/model.py

@@ -684,6 +684,22 @@ def init_from_ply(self, mogt_path:str, init_model=True):
 
         extra_f_names = [p.name for p in plydata.elements[0].properties if p.name.startswith("f_rest_")]
         extra_f_names = sorted(extra_f_names, key = lambda x: int(x.split('_')[-1]))
+
+        # Auto-detect SH degree for Isaac Sim compatibility
+        if len(extra_f_names) == 0:
+            # DC-only PLY: automatically set max_n_features to 0
+            if self.max_n_features != 0:
+                print(f"Auto-detected DC-only PLY file: adjusting max_n_features from {self.max_n_features} to 0 for Isaac Sim compatibility")
+                self.max_n_features = 0
+        elif len(extra_f_names) % 3 == 0:
+            # Infer SH degree from available f_rest properties
+            num_speculars_available = len(extra_f_names) // 3
+            import math
+            inferred_degree = int(round(math.sqrt(num_speculars_available + 1) - 1))
+            if self.max_n_features != inferred_degree:
+                print(f"Auto-detected SH degree {inferred_degree} from PLY file: adjusting max_n_features from {self.max_n_features} to {inferred_degree}")
+                self.max_n_features = inferred_degree
+
         num_speculars = (self.max_n_features + 1) ** 2 - 1
         assert len(extra_f_names)==3*num_speculars
         mogt_specular = np.zeros((num_gaussians, len(extra_f_names)))