force hessian symmetric

Author: Huangzizhou

src/ipc/potentials/friction_potential.cpp

@@ -549,7 +549,6 @@ FrictionPotential::force_jacobian(
     assert(rest_positions.size() == lagged_displacements.size());
     assert(lagged_displacements.size() == velocities.size());
     const int n = rest_positions.size();
-    const int dim = n / collision.num_vertices();
     assert(n % collision.num_vertices() == 0);
 
     // const Vector<double, -1, FrictionPotential::element_size> x =

src/ipc/smooth_contact/collisions/smooth_collision.cpp

@@ -375,7 +375,8 @@ SmoothCollisionTemplate<max_vert, PrimitiveA, PrimitiveB>::hessian(
     gOrient(core_indices) += gBarrier * orient;
     orient *= barrier;
 
-    return hOrient;
+    // return hOrient
+    return (hOrient + hOrient.transpose()) / 2.;
 }
 
 // ---- distance ----