Move computation of flex_vert0 to user_mesh.cc.

This removes the dependency of flex_vert0 from mj_flex and mjData.

PiperOrigin-RevId: 700382297
Change-Id: I0b6d023c2e1ba14fa92417b65bfc288f37c223ae

src/user/user_mesh.cc

@@ -2944,6 +2944,16 @@ void mjCFlex::Compile(const mjVFS* vfs) {
 
   // create bounding volume hierarchy
   CreateBVH();
+
+  // compute bounding box coordinates
+  vert0_.assign(3*nvert, 0);
+  const mjtNum* bvh = tree.Bvh().data();
+  for (int j=0; j < nvert; j++) {
+    for (int k=0; k < 3; k++) {
+      double size = 2*(bvh[k+3] - radius);
+      vert0_[3*j+k] = (vertxpos[3*j+k] - bvh[k]) / size + 0.5;
+    }
+  }
 }
 
 

src/user/user_model.cc

@@ -2825,6 +2825,9 @@ void mjCModel::CopyObjects(mjModel* m) {
       mjuu_copyvec(m->flex_vert + 3*vert_adr, pfl->vert_.data(), 3*pfl->nvert);
     }
 
+    // copy vert0
+    mjuu_copyvec(m->flex_vert0 + 3*vert_adr, pfl->vert0_.data(), 3*pfl->nvert);
+
     // copy or set vertbodyid
     if (pfl->rigid) {
       for (int k=0; k<pfl->nvert; k++) {

src/user/user_objects.h

@@ -774,6 +774,8 @@ class mjCFlex: public mjCFlex_, private mjsFlex {
   void Compile(const mjVFS* vfs);         // compiler
   void CreateBVH(void);                   // create flex BVH
   void CreateShellPair(void);             // create shells and evpairs
+
+  std::vector<double> vert0_;             // vertex positions in [0, 1]^d in the bounding box
 };