take a look: void f() { static D3DXMATRIX matrix; ZeroMemory(&matrix, sizeof(D3DXMATRIX)); .... } this way,every time the matrix will be zero. so how to have this way: static D3DXMATRIX matrix = ZeroMemroy(...); I know this not work,just give some tip. so how to do? I must do this way? int static i = 0;i++;if (i ==1)ZeroMemory(&matrix, sizeof(D3DXMATRIX));