--expand calculation to test for mesh topology - watertight and manifold.

Author: jturner65

src/esp/assets/ResourceManager.cpp

@@ -1058,37 +1058,86 @@ void ResourceManager::computeGeneralMeshAreaAndVolume(
         meshData->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();
+    // # of indices
+    uint32_t numIdxs = meshData->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
+    std::unordered_map<uint64_t, int> edgeCount;
+    std::unordered_map<uint64_t, int> altEdgeCount;
+    scene::DrawableMeshTopology meshTopology =
+        scene::DrawableMeshTopology::ClosedManifold;
+    for (uint32_t idx = 0; idx < numIdxs; idx += 3) {
+      uint64_t vals[] = {uint64_t(idxAra[idx]), uint64_t(idxAra[idx + 1]),
+                         uint64_t(idxAra[idx + 2])};
+      uint64_t shift_vals[] = {vals[0] << 32, vals[1] << 32, vals[2] << 32};
+      // for each edge in poly
+      for (uint32_t i = 0; i < 3; ++i) {
+        uint32_t next_i = (i + 1) % 3;
+        auto res =
+            edgeCount.emplace(std::make_pair(shift_vals[i] + vals[next_i], 0));
+        if (!res.second) {
+          res.first->second += 1;
+          // Duplicate edge with same orientation
+          meshTopology = scene::DrawableMeshTopology::NonManifold;
+        }
+        // Alt edge placement - verify the alternate edge is present
+        altEdgeCount.emplace(std::make_pair(shift_vals[next_i] + vals[i], 0));
+      }
+    }
+    // If still closed manifold then check that every edge has an alt edge
+    // present
+    if (meshTopology == scene::DrawableMeshTopology::ClosedManifold) {
+      for (const auto entry : edgeCount) {
+        altEdgeCount.erase(entry.first);
+      }
+      if (altEdgeCount.size() > 0) {
+        meshTopology = scene::DrawableMeshTopology::OpenManifold;
+      }
+    }
+
+    // locate the scene node which contains the current drawable
+    scene::SceneNode& node = staticDrawableInfo[iEntry].node;
     // Surface area of the mesh : .5 * ba.cross(bc)
     double ttlSurfaceArea = 0.0;
-
     // Volume of the mesh : 1/6 * (OA.dot(ba.cross(bc)))
     // Where O is a distant vertex
+    // Only applicable on closed manifold meshes (i.e. all edges have exactly
+    // 2 faces)
     double ttlVolume = 0.0f;
-
-    // locate the scene node which contains the current drawable
-    scene::SceneNode& node = staticDrawableInfo[iEntry].node;
-    // # of indices
-    int numIdxs = meshData->indexCount();
-
-    // const auto idxView = meshData->indices<std::uint32_t>();
-    const auto idxView = meshData->indicesAsArray();
-    Mn::Vector3 distPt{1000, 1000, 1000};
-    for (uint32_t rawIdx = 0; rawIdx < numIdxs; rawIdx += 3) {
-      const auto aVert = posArray[idxView[rawIdx + 1]];
-      Mn::Vector3 a = posArray[idxView[rawIdx]] - aVert;
-      Mn::Vector3 b = posArray[idxView[rawIdx + 2]] - aVert;
-      Mn::Vector3 areaNorm = 0.5 * Mn::Math::cross(a, b);
-      double surfArea = areaNorm.length();
-      ttlSurfaceArea += surfArea;
-      Mn::Vector3 c = distPt - aVert;
-      double signedVol = (Mn::Math::dot(c, areaNorm)) / 3.0;
-      ttlVolume += signedVol;
+    if (meshTopology == scene::DrawableMeshTopology::ClosedManifold) {
+      Mn::Vector3 origin{};
+      for (uint32_t idx = 0; idx < numIdxs; idx += 3) {
+        const auto aVert = posArray[idxAra[idx + 1]];
+        Mn::Vector3 aVec = posArray[idxAra[idx]] - aVert;
+        Mn::Vector3 bVec = posArray[idxAra[idx + 2]] - aVert;
+        Mn::Vector3 areaNormVec = 0.5 * Mn::Math::cross(aVec, bVec);
+        double surfArea = areaNormVec.length();
+        ttlSurfaceArea += surfArea;
+        Mn::Vector3 c = origin - aVert;
+        double signedVol = (Mn::Math::dot(c, areaNormVec)) / 3.0;
+        ttlVolume += signedVol;
+      }
+    } else {
+      // Open or non-manifold meshes won't have an accurate volume calc
+      for (uint32_t idx = 0; idx < numIdxs; idx += 3) {
+        const auto aVert = posArray[idxAra[idx + 1]];
+        Mn::Vector3 aVec = posArray[idxAra[idx]] - aVert;
+        Mn::Vector3 bVec = posArray[idxAra[idx + 2]] - aVert;
+        Mn::Vector3 areaNormVec = 0.5 * Mn::Math::cross(aVec, bVec);
+        double surfArea = areaNormVec.length();
+        ttlSurfaceArea += surfArea;
+      }
     }
-
     // set the node's volume and surface area
     node.setMeshVolume(ttlVolume);
     node.setMeshSurfaceArea(ttlSurfaceArea);
-
+    // Set whether the mesh is manifold and/or closed/watertight
+    node.setMeshTopology(meshTopology);
   }  // iEntry
 
 }  // ResourceManager::computeGeneralMeshVolume
@@ -3196,9 +3245,9 @@ void ResourceManager::addComponent(
                    drawableConfig);     // instance skinning data
 
     // compute the bounding box for the mesh we are adding
-    if (computeAbsoluteAABBs) {
-      staticDrawableInfo.emplace_back(StaticDrawableInfo{node, meshID});
-    }
+    // if (computeAbsoluteAABBs) {
+    staticDrawableInfo.emplace_back(StaticDrawableInfo{node, meshID});
+    //}
     BaseMesh* meshBB = meshes_.at(meshID).get();
     node.setMeshBB(computeMeshBB(meshBB));
   }

src/esp/scene/SceneNode.h

@@ -40,6 +40,15 @@ enum class SceneNodeType {
   OBJECT = 4,  // objects added via physics api
 };
 
+// Topological nature of the drawable mesh held by this scene node, if exists
+enum class DrawableMeshTopology {
+  Unknown = ID_UNDEFINED,
+  ClosedManifold = 0,
+  NonManifold,
+  OpenManifold
+
+};
+
 /**
  * @brief This enum holds the idx values for the vector of various types
  * of IDs that can be rendered via semantic sensors.
@@ -293,6 +302,11 @@ class SceneNode : public MagnumObject,
   //! set frustum plane in last frame that culls this node
   void setFrustumPlaneIndex(int index) { frustumPlaneIndex = index; };
 
+  DrawableMeshTopology getMeshTopology() const { return isClosedManifold_; }
+
+  void setMeshTopology(DrawableMeshTopology _isClosedManifold) {
+    isClosedManifold_ = _isClosedManifold;
+  }
   //! Set this node's drawable's volume
   void setMeshVolume(double _volume) { volume_ = _volume; }
   //! Get this node's drawable's volume
@@ -341,11 +355,15 @@ class SceneNode : public MagnumObject,
   //! The absolute translation of this node, updated in clean
   Magnum::Matrix4 absoluteTransformation_;
 
+  //! Whether the drawable mesh is closed and manifold (ever edge is adjacent to
+  //! exactly 2 faces)
+  DrawableMeshTopology isClosedManifold_ = DrawableMeshTopology::Unknown;
+
   //! The volume of the drawable mesh held in this node
-  double volume_ = 0.0f;
+  double volume_ = 0.0;
 
   //! The surface area of the drawable mesh held in this node
-  double surfArea_ = 0.0f;
+  double surfArea_ = 0.0;
 
   //! the global bounding box for *static* meshes stored at this node
   //  NOTE: this is different from the local bounding box meshBB_ defined above: