Working on ConvexMesh

Author: DanielChappuis

include/reactphysics3d/collision/ConvexMesh.h

@@ -70,6 +70,9 @@ class ConvexMesh {
         /// Mesh maximum bounds in the three local x, y and z directions
         Vector3 mMaxBounds;
 
+        /// Volume of the mesh
+        decimal mVolume;
+
         // -------------------- Methods -------------------- //
 
         /// Constructor
@@ -90,6 +93,9 @@ class ConvexMesh {
         /// Compute and return the face normal (not normalized)
         Vector3 computeFaceNormal(uint32 faceIndex) const;
 
+        /// Compute the volume of the mesh
+        void computeVolume();
+
         /// Static factory method to create a convex mesh
         static ConvexMesh* create(MemoryAllocator& allocator);
 
@@ -124,6 +130,9 @@ class ConvexMesh {
         /// Compute and return the volume of the mesh
         decimal getVolume() const;
 
+        /// Return the local inertia tensor of the mesh
+        Vector3 getLocalInertiaTensor(decimal mass, Vector3 scale) const;
+
         // ---------- Friendship ---------- //
 
         friend class PhysicsCommon;
@@ -197,6 +206,34 @@ RP3D_FORCE_INLINE const Vector3& ConvexMesh::getMaxBounds() const {
     return mMaxBounds;
 }
 
+// Return the volume of the convex mesh
+/**
+ * @return The volume of the mesh
+ */
+RP3D_FORCE_INLINE decimal ConvexMesh::getVolume() const {
+   return mVolume;
+}
+
+// Return the local inertia tensor of the mesh
+/// The local inertia tensor of the convex mesh is approximated using the inertia tensor
+/// of its bounding box.
+/**
+* @param mass Mass to use to compute the inertia tensor of the collision shape
+* @param scale Scaling factor for the mesh
+*/
+RP3D_FORCE_INLINE Vector3 ConvexMesh::getLocalInertiaTensor(decimal mass, Vector3 scale) const {
+
+    // TODO: We should compute a much better inertia tensor here (not using a box)
+
+    const decimal factor = (decimal(1.0) / decimal(3.0)) * mass;
+    const Vector3 realExtent = decimal(0.5) * scale * (getMaxBounds() - getMinBounds());
+    assert(realExtent.x > 0 && realExtent.y > 0 && realExtent.z > 0);
+    const decimal xSquare = realExtent.x * realExtent.x;
+    const decimal ySquare = realExtent.y * realExtent.y;
+    const decimal zSquare = realExtent.z * realExtent.z;
+    return Vector3(factor * (ySquare + zSquare), factor * (xSquare + zSquare), factor * (xSquare + ySquare));
+}
+
 }
 
 #endif

include/reactphysics3d/collision/shapes/ConvexMeshShape.h

@@ -172,16 +172,7 @@ RP3D_FORCE_INLINE void ConvexMeshShape::getLocalBounds(Vector3& min, Vector3& ma
 * @param mass Mass to use to compute the inertia tensor of the collision shape
 */
 RP3D_FORCE_INLINE Vector3 ConvexMeshShape::getLocalInertiaTensor(decimal mass) const {
-
-    // TODO: We should compute a much better inertia tensor here (not using a box)
-
-    const decimal factor = (decimal(1.0) / decimal(3.0)) * mass;
-    const Vector3 realExtent = decimal(0.5) * mScale * (mConvexMesh->getMaxBounds() - mConvexMesh->getMinBounds());
-    assert(realExtent.x > 0 && realExtent.y > 0 && realExtent.z > 0);
-    const decimal xSquare = realExtent.x * realExtent.x;
-    const decimal ySquare = realExtent.y * realExtent.y;
-    const decimal zSquare = realExtent.z * realExtent.z;
-    return Vector3(factor * (ySquare + zSquare), factor * (xSquare + zSquare), factor * (xSquare + ySquare));
+    return mConvexMesh->getLocalInertiaTensor(mass, mScale);
 }
 
 // Return the number of faces of the mesh
@@ -236,7 +227,7 @@ RP3D_FORCE_INLINE Vector3 ConvexMeshShape::getCentroid() const {
 
 // Compute and return the volume of the collision shape
 RP3D_FORCE_INLINE decimal ConvexMeshShape::getVolume() const {
-    return mConvexMesh->getVolume();
+    return mConvexMesh->getVolume() * mScale.x * mScale.y * mScale.z;
 }
 
 }

src/collision/ConvexMesh.cpp

@@ -42,7 +42,7 @@ using namespace reactphysics3d;
  */
 ConvexMesh::ConvexMesh(MemoryAllocator& allocator)
                : mMemoryAllocator(allocator), mHalfEdgeStructure(allocator, 6, 8, 24),
-                 mVertices(allocator), mFacesNormals(allocator), mMinBounds(0, 0, 0), mMaxBounds(0, 0, 0)  {
+                 mVertices(allocator), mFacesNormals(allocator), mMinBounds(0, 0, 0), mMaxBounds(0, 0, 0), mVolume(0) {
 
 }
 
@@ -73,6 +73,9 @@ bool ConvexMesh::init(const PolygonVertexArray& polygonVertexArray, std::vector<
     // Compute the faces normals
     isValid &= computeFacesNormals(errors);
 
+    // Compute the volume of the mesh
+    computeVolume();
+
    return isValid;
 }
 
@@ -206,19 +209,6 @@ bool ConvexMesh::computeFacesNormals(std::vector<Error>& errors) {
 
         if (face.faceVertices.size() >= 3) {
 
-            auto test0 = face.faceVertices[0];
-            auto test1 = face.faceVertices[1];
-            auto test2 = face.faceVertices[2];
-
-            auto v0 = getVertex(face.faceVertices[0]);
-            auto v1 = getVertex(face.faceVertices[1]);
-            auto v2 = getVertex(face.faceVertices[2]);
-            auto v3 = Vector3(0, 0, 0);
-            if (face.faceVertices.size() > 3) {
-
-                v3 = getVertex(face.faceVertices[3]);
-            }
-
             mFacesNormals.add(computeFaceNormal(f));
             decimal normalLength = mFacesNormals[f].length();
 
@@ -258,9 +248,9 @@ Vector3 ConvexMesh::computeFaceNormal(uint32 faceIndex) const {
     return normal;
 }
 
-// Compute and return the volume of the convex mesh
+// Compute the volume of the convex mesh
 /// We use the divergence theorem to compute the volume of the convex mesh using a sum over its faces.
-decimal ConvexMesh::getVolume() const {
+void ConvexMesh::computeVolume() {
 
     decimal sum = 0.0;
 
@@ -275,5 +265,5 @@ decimal ConvexMesh::getVolume() const {
         sum += faceVertex.dot(faceNormal) * faceArea;
     }
 
-    return std::abs(sum) / decimal(3.0);
+    mVolume = std::abs(sum) / decimal(3.0);
 }

testbed/common/ConvexMesh.cpp

@@ -263,4 +263,3 @@ int ConvexMesh::findVertexIndex(const std::vector<openglframework::Vector3>& ver
 
 	return -1;
 }
-