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Fix USD volume range and skip NanoVDB grids with no active voxels #200

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Fix USD volume range and skip NanoVDB grids with no active voxels #200

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28 changes: 28 additions & 0 deletions tsd/src/tsd/io/importers/import_NVDB.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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());
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Copilot AI Jan 19, 2026

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The field object is being removed from the scene after it was just created. Consider skipping field creation entirely when there are no active voxels to avoid unnecessary object creation and cleanup overhead. Check for active voxels before creating the field object.

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return {};
}

if (!metadata->hasMinMax()) {
switch (metadata->gridType()) {
case nanovdb::GridType::Fp4: {
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6 changes: 4 additions & 2 deletions tsd/src/tsd/io/importers/import_USD.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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>(
Expand All @@ -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;
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