--exit calc if not strictly triangle-based mesh; make temp dedup copy

src/esp/assets/ResourceManager.cpp

@@ -1048,22 +1048,30 @@ void ResourceManager::computeGeneralMeshAreaAndVolume(
 
     Cr::Containers::Optional<Mn::Trade::MeshData>& meshData =
         meshes_.at(meshID)->getMeshData();
+    if (meshData->primitive() != Mn::MeshPrimitive::Triangles) {
+      // These calculations rely on this mesh being purely triangle-based
+      continue;
+    }
     CORRADE_ASSERT(
         meshData,
         "::computeGeneralMeshAreaAndVolume: The mesh data specified at ID:"
             << meshID << "is empty/undefined. Aborting", );
+    // Make temp copy that removes dupes for volume calc
+    Cr::Containers::Optional<Mn::Trade::MeshData> newMeshData =
+        Mn::MeshTools::removeDuplicates(Mn::MeshTools::filterOnlyAttributes(
+            *meshData, {Mn::Trade::MeshAttribute::Position}));
 
     // Precalc all transformed verts - only use first position array for this
     Cr::Containers::Array<Mn::Vector3> posArray =
-        meshData->positions3DAsArray(0);
+        newMeshData->positions3DAsArray(0);
     Mn::MeshTools::transformPointsInPlace(absTransforms[iEntry], posArray);
 
     // Getting the view properly relies on having the appropriate type of the
     // loaded data
-    // const auto idxView = meshData->indices<std::uint32_t>();
-    const auto idxAra = meshData->indicesAsArray();
+    // const auto idxView = newMeshData->indices<std::uint32_t>();
+    const auto idxAra = newMeshData->indicesAsArray();
     // # of indices
-    uint32_t numIdxs = meshData->indexCount();
+    uint32_t numIdxs = newMeshData->indexCount();
     // Assuming no duplicate vertices with different idxs
     // Determine that all edges have exactly 2 sides ->
     // idxAra describes exactly 2 pairs of the same idxs, a->b and b->a