Fix left handed indexed meshes with normals (#2233)

* Fix problem with left handed indexed meshes with normals rendered with husk * store the mesh handedness to avoid calling GetTopology
Autodesk · Feb 11, 2025 · fd41c44 · fd41c44
1 parent e4c49e9
commit fd41c44
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Showing 3 changed files with 11 additions and 12 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -16,6 +16,7 @@
 - [usd#2219](https://github.com/Autodesk/arnold-usd/issues/2219) - Fix race condition in hydra with node names
 - [usd#2225](https://github.com/Autodesk/arnold-usd/issues/2225) - Fix crash in point instancers with missing prototypes
 - [usd#2224](https://github.com/Autodesk/arnold-usd/issues/2224) - Fix warning "HdArnoldDriverMain is already installed" 
+- [usd#2232](https://github.com/Autodesk/arnold-usd/issues/2232) - Fix incorrect husk render of left handed indexed meshes with normals.
 
 ## Pending Feature release
 

diff --git a/libs/render_delegate/mesh.cpp b/libs/render_delegate/mesh.cpp
@@ -204,7 +204,6 @@ void HdArnoldMesh::Sync(
     HdArnoldRenderParamInterrupt param(renderParam);
     const auto& id = GetId();
     HdArnoldSampledPrimvarType _pointsSample;
-    VtValue vertexCountsVtValue;     ///< Vertex nsides
     const auto dirtyPrimvars = HdArnoldGetComputedPrimvars(sceneDelegate, id, *dirtyBits, _primvars, nullptr, &_pointsSample) ||
                                (*dirtyBits & HdChangeTracker::DirtyPrimvar);
 
@@ -235,15 +234,12 @@ void HdArnoldMesh::Sync(
         }
     }
 
-    bool isLeftHanded = false;
-
+    // We have to flip the orientation if it's left handed.
     const auto dirtyTopology = HdChangeTracker::IsTopologyDirty(*dirtyBits, id);
     if (dirtyTopology) {
-        param.Interrupt();
         const auto topology = GetMeshTopology(sceneDelegate);
-        // We have to flip the orientation if it's left handed.
-        isLeftHanded = topology.GetOrientation() == PxOsdOpenSubdivTokens->leftHanded;
-
+        _isLeftHanded = topology.GetOrientation() == PxOsdOpenSubdivTokens->leftHanded;
+        param.Interrupt();
         // Keep a reference on the vertex buffers as long as this object is live
         // We try to keep the buffer consts as otherwise usd will duplicate them (COW)
         const VtIntArray &vertexCounts = topology.GetFaceVertexCounts();
@@ -255,14 +251,14 @@ void HdArnoldMesh::Sync(
         const bool hasNegativeValues = std::any_of(vertexCounts.cbegin(), vertexCounts.cend(), [](int i) {return i < 0;});
         _vertexCountSum = 0;
         // If the buffer is left handed or has negative values, we must allocate a new one to make it work with arnold
-        if (isLeftHanded || hasNegativeValues) {
+        if (_isLeftHanded || hasNegativeValues) {
             VtIntArray vertexCountsTmp = topology.GetFaceVertexCounts();
             VtIntArray vertexIndicesTmp = topology.GetFaceVertexIndices();
             assert(vertexCountsTmp.size() == (size_t)numFaces);
             if (Ai_unlikely(hasNegativeValues)) {
                 std::transform(vertexCountsTmp.cbegin(), vertexCountsTmp.cend(), vertexCountsTmp.begin(), [] (const int i){return i < 0 ? 0 : i;});
             }
-            if (isLeftHanded) {
+            if (_isLeftHanded) {
                 for (int i = 0; i < numFaces; ++i) {
                     const int vertexCount = vertexCountsTmp[i];
                     for (int vertexIdx = 0; vertexIdx < vertexCount; vertexIdx += 1) {
@@ -274,14 +270,14 @@ void HdArnoldMesh::Sync(
                 _vertexCountSum = std::accumulate(vertexCounts.cbegin(), vertexCounts.cend(), 0);
             }
             // Keep the buffers alive
-            vertexCountsVtValue = VtValue(vertexCountsTmp);
+            _vertexCountsVtValue = VtValue(vertexCountsTmp);
             AiNodeSetArray(GetArnoldNode(), str::nsides, _arrayHandler.CreateAtArrayFromVtArray(vertexCountsTmp, AI_TYPE_UINT));
             AiNodeSetArray(GetArnoldNode(), str::vidxs, _arrayHandler.CreateAtArrayFromVtArray(vertexIndicesTmp, AI_TYPE_UINT));
 
         } else {
             _vertexCountSum = std::accumulate(vertexCounts.cbegin(), vertexCounts.cend(), 0);
             // Keep the buffers alive
-            vertexCountsVtValue = VtValue(vertexCounts);
+            _vertexCountsVtValue = VtValue(vertexCounts);
             AiNodeSetArray(GetArnoldNode(), str::nsides, _arrayHandler.CreateAtArrayFromVtArray(vertexCounts, AI_TYPE_UINT));
             AiNodeSetArray(GetArnoldNode(), str::vidxs, _arrayHandler.CreateAtArrayFromVtArray(vertexIndices, AI_TYPE_UINT));
         }
@@ -380,7 +376,7 @@ void HdArnoldMesh::Sync(
         param.Interrupt();
         const auto isVolume = _IsVolume();
         AtNode *meshLight = _GetMeshLight(sceneDelegate, id);
-        const VtIntArray *leftHandedVertexCounts = isLeftHanded ? & vertexCountsVtValue.UncheckedGet<VtIntArray>() : nullptr;
+        const VtIntArray *leftHandedVertexCounts = _isLeftHanded ? & _vertexCountsVtValue.UncheckedGet<VtIntArray>() : nullptr;
         for (auto& primvar : _primvars) {
             auto& desc = primvar.second;
             // If the positions have changed, then all non-constant primvars must be updated

diff --git a/libs/render_delegate/mesh.h b/libs/render_delegate/mesh.h
@@ -94,6 +94,8 @@ class HdArnoldMesh : public HdArnoldRprim<HdMesh> {
 
     HdArnoldPrimvarMap _primvars;     ///< Precomputed list of primvars.
     HdArnoldSubsets _subsets;         ///< Material ids from subsets.
+    VtValue _vertexCountsVtValue;      ///< Vertex nsides. We need to keep it alive for left handed geometries.
+    bool _isLeftHanded = false;       ///< Whether the geometry is left handed or not.
     size_t _vertexCountSum = 0;       ///< Sum of the vertex counts array.
     size_t _numberOfPositionKeys = 1; ///< Number of vertex position keys for the mesh.
     AtNode *_geometryLight = nullptr; ///< Eventual mesh light for this polymesh