Compute the interpolation coefficients per vertex rather than per node.

PiperOrigin-RevId: 792124681
Change-Id: Ib0e18d0b59f09c7e3bdb2ef9940a9b7327b92cd3

src/user/user_mesh.cc

@@ -780,11 +780,15 @@ void mjCMesh::TryCompile(const mjVFS* vfs) {
     if (!plugin.active) {
       tmd::TriangleMeshDistance sdf(vert_.data(), nvert(), face_.data(), nface());
 
+      std::vector<double> coeffs(octree_.NumVerts());
+      for (int i = 0; i < octree_.NumVerts(); ++i) {
+        coeffs[i] = sdf.signed_distance(octree_.Vert(i)).distance;
+      }
+
       // TODO: the value at hanging vertices should be computed from the parent
       for (int i = 0; i < octree_.NumNodes(); ++i) {
         for (int j = 0; j < 8; j++) {
-            const double* v = octree_.Vert(i, j);
-            octree_.AddCoeff(i, j, sdf.signed_distance(v).distance);
+            octree_.AddCoeff(i, j, coeffs[octree_.VertId(i, j)]);
         }
       }
     }

src/user/user_objects.h

@@ -275,7 +275,8 @@ class mjCOctree : public mjCOctree_ {
   void CopyChild(int* child) const;
   void CopyAabb(mjtNum* aabb) const;
   void CopyCoeff(mjtNum* coeff) const;
-  const double* Vert(int n, int v) const { return vert_[node_[n].vertid[v]].p.data(); }
+  const double* Vert(int i) const { return vert_[i].p.data(); }
+  int VertId(int n, int v) const { return node_[n].vertid[v]; }
   void SetFace(const std::vector<double>& vert, const std::vector<int>& face);
   int Size() const {
     return sizeof(OctNode) * node_.size() + sizeof(Triangle) * face_.size() +