unity quad mesh collider not following quad vertex change -

its single quad 4 vertices , meshcollider: during update vertex positions changed in each frame animation meshcollider sit fix @ original created position.

i'd googled many nothing come close that. i'd tried toggled convex checkbox not following size of changes , meshcollider stayed fix , bigger actual quad.

someone experience please advise. in advance effort appreciated.

following snippet of vertex change , mesh recalculate lines:

    animeshcollidertest:     switch(btn.starget){     case "open":{         btn.v3a_vertex[0].x -= btn.fdeltax;         btn.v3a_vertex[0].y -= btn.fdeltay;         btn.v3a_vertex[1].x += btn.fdeltax;            btn.v3a_vertex[1].y -= btn.fdeltay;         btn.v3a_vertex[2].x -= btn.fdeltax;         btn.v3a_vertex[2].y += btn.fdeltay;         btn.v3a_vertex[3].x += btn.fdeltax;         btn.v3a_vertex[3].y += btn.fdeltay;         // debug.log("thumbpadctxseqc2:animeshcollidertest:1380:btn.v3a_vertex[0].y:" + btn.v3a_vertex[0].y + ", v3a_vertex[1].y:" + btn.v3a_vertex[1].y);     }break;              btn.g.getcomponent<meshfilter>().mesh.vertices = btn.v3a_vertex;     btn.g.getcomponent<meshfilter>().mesh.recalculatenormals();     btn.g.getcomponent<meshfilter>().mesh.recalculatebounds();