From 14a1ab26980f53cffa21b5d0cc7c64dc428bab45 Mon Sep 17 00:00:00 2001
From: Andrea Paris <aparis@nvidia.com>
Date: Mon, 19 Jan 2026 08:57:32 +0100
Subject: [PATCH 1/2] Fix USD volume range and skip NanoVDB grids with no
 active voxels

---
 tsd/src/tsd/io/importers/import_NVDB.cpp | 28 ++++++++++++++++++++++++
 tsd/src/tsd/io/importers/import_USD.cpp  |  6 +++--
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/tsd/src/tsd/io/importers/import_NVDB.cpp b/tsd/src/tsd/io/importers/import_NVDB.cpp
index 53e7433da..897502317 100644
--- a/tsd/src/tsd/io/importers/import_NVDB.cpp
+++ b/tsd/src/tsd/io/importers/import_NVDB.cpp
@@ -30,6 +30,34 @@ SpatialFieldRef import_NVDB(Scene &scene, const char *filepath)
   try {
     auto grid = nanovdb::io::readGrid(filepath);
     auto metadata = grid.gridMetaData();
+
+    bool hasActiveVoxels = false;
+    switch (metadata->gridType()) {
+    case nanovdb::GridType::Fp4:
+      hasActiveVoxels = grid.grid<nanovdb::Fp4>()->activeVoxelCount() > 0;
+      break;
+    case nanovdb::GridType::Fp8:
+      hasActiveVoxels = grid.grid<nanovdb::Fp8>()->activeVoxelCount() > 0;
+      break;
+    case nanovdb::GridType::Fp16:
+      hasActiveVoxels = grid.grid<nanovdb::Fp16>()->activeVoxelCount() > 0;
+      break;
+    case nanovdb::GridType::FpN:
+      hasActiveVoxels = grid.grid<nanovdb::FpN>()->activeVoxelCount() > 0;
+      break;
+    case nanovdb::GridType::Float:
+      hasActiveVoxels = grid.grid<float>()->activeVoxelCount() > 0;
+      break;
+    default:
+      break;
+    }
+
+    if (!hasActiveVoxels) {
+      logStatus("[import_NVDB] no active voxels, skipping '%s'", filepath);
+      scene.removeObject(field.data());
+      return {};
+    }
+
     if (!metadata->hasMinMax()) {
       switch (metadata->gridType()) {
       case nanovdb::GridType::Fp4: {
diff --git a/tsd/src/tsd/io/importers/import_USD.cpp b/tsd/src/tsd/io/importers/import_USD.cpp
index e30ce42f9..2f1b26208 100644
--- a/tsd/src/tsd/io/importers/import_USD.cpp
+++ b/tsd/src/tsd/io/importers/import_USD.cpp
@@ -910,7 +910,8 @@ static void import_usd_volume(Scene &scene,
   VolumeTransferFunction tf = get_volume_transfer_function(prim);
 
   ArrayRef colorArray;
-  math::float2 valueRange;
+  // Default to the field's value range to avoid undefined ranges.
+  math::float2 valueRange = field->computeValueRange();
 
   // Create a volume node and assign the field, color map, and value range
   auto [inst, volume] = scene.insertNewChildObjectNode<Volume>(
@@ -922,7 +923,8 @@ static void import_usd_volume(Scene &scene,
     // Use transfer function from USD material
     colorArray = scene.createArray(ANARI_FLOAT32_VEC4, tf.colors.size());
     colorArray->setData(tf.colors.data(), tf.colors.size());
-    valueRange = tf.domain;
+    if (tf.domain.x < tf.domain.y)
+      valueRange = tf.domain;
 
     // Create opacity control points from USD transfer function
     std::vector<math::float2> opacityControlPoints;

From de6d0e7c83e66e99179e6f3aa65d7c1adaeac4f4 Mon Sep 17 00:00:00 2001
From: Andrea Paris <aparis@nvidia.com>
Date: Fri, 6 Feb 2026 09:14:25 +0100
Subject: [PATCH 2/2] Added environment variable to decide on invalid nvdbs

---
 tsd/CMakeLists.txt                       |  2 ++
 tsd/src/tsd/io/CMakeLists.txt            |  6 ++++++
 tsd/src/tsd/io/importers/import_NVDB.cpp | 11 +++++++----
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/tsd/CMakeLists.txt b/tsd/CMakeLists.txt
index baba550af..85e2ab75e 100644
--- a/tsd/CMakeLists.txt
+++ b/tsd/CMakeLists.txt
@@ -59,6 +59,8 @@ option(TSD_USE_TORCH "Use PyTorch for importing neural geometries" OFF)
 option(TSD_USE_VTK "Use VTK for importing VTK file formats" OFF)
 option(TSD_USE_SILO "Use Silo for importing Silo file formats" OFF)
 option(TSD_USE_MPI "Enable MPI support" OFF)
+option(TSD_NANOVDB_SKIP_INVALID_VOLUMES
+  "Skip NanoVDB volumes with zero active voxels" OFF)
 
 if (APPLE)
   set(TSD_USE_CUDA OFF)
diff --git a/tsd/src/tsd/io/CMakeLists.txt b/tsd/src/tsd/io/CMakeLists.txt
index bc49ad184..4d4bc7cc5 100644
--- a/tsd/src/tsd/io/CMakeLists.txt
+++ b/tsd/src/tsd/io/CMakeLists.txt
@@ -141,3 +141,9 @@ if (TSD_USE_SILO)
 else()
   project_compile_definitions(PRIVATE -DTSD_USE_SILO=0)
 endif()
+
+if (TSD_NANOVDB_SKIP_INVALID_VOLUMES)
+  project_compile_definitions(PRIVATE -DTSD_NANOVDB_SKIP_INVALID_VOLUMES=1)
+else()
+  project_compile_definitions(PRIVATE -DTSD_NANOVDB_SKIP_INVALID_VOLUMES=0)
+endif()
diff --git a/tsd/src/tsd/io/importers/import_NVDB.cpp b/tsd/src/tsd/io/importers/import_NVDB.cpp
index 897502317..1e30c26c3 100644
--- a/tsd/src/tsd/io/importers/import_NVDB.cpp
+++ b/tsd/src/tsd/io/importers/import_NVDB.cpp
@@ -23,7 +23,6 @@ SpatialFieldRef import_NVDB(Scene &scene, const char *filepath)
   std::string file = fileOf(filepath);
   if (file.empty())
     return {};
-
   auto field = scene.createObject<SpatialField>(tokens::spatial_field::nanovdb);
   field->setName(file.c_str());
 
@@ -53,9 +52,13 @@ SpatialFieldRef import_NVDB(Scene &scene, const char *filepath)
     }
 
     if (!hasActiveVoxels) {
-      logStatus("[import_NVDB] no active voxels, skipping '%s'", filepath);
-      scene.removeObject(field.data());
-      return {};
+      logWarning("[import_NVDB] no active voxels in '%s'", filepath);
+      if (TSD_NANOVDB_SKIP_INVALID_VOLUMES) {
+        logStatus(
+            "[import_NVDB] skipping due to TSD_NANOVDB_SKIP_INVALID_VOLUMES");
+        scene.removeObject(field.data());
+        return {};
+      }
     }
 
     if (!metadata->hasMinMax()) {