let me explain with sample:   vertiex :   p1: 0,0,0                                  uv : 0.0,0.0 p2: 0,0,1                                  uv : 0.5,0.0 p3: 1,0,0 : face 1(p1,p2,p3)     uv : 0.0,0.5 p4: 1,0,1 : face 2(p2,p3,p4)     uv : 0.5,0.5   everything is ok to p4 so i want fill back face with out append more vertex   so    face 3 (p4,p2,p3)   :   i cant set any new uv  face 4 (p3,p1,p2)   :   *** same problem    * in babylonjs i can set uv per  vertex  but in .obj format i