Function belt draw surface by belts. You can use ‘x’ style for drawing lines in other direction.
MGL code:
call 'prepare2d' title 'Belt plot':rotate 50 60:box:belt a
C++ code:
void smgl_belt(mglGraph *gr) { mglData a; mgls_prepare2d(&a); if(big!=3) gr->Title("Belt plot"); gr->Rotate(50,60); gr->Box(); gr->Belt(a); }