This routine converts MESH and GRID structures into POLYGONS structures. If the first argument is a GRID or MESH structure, then the result is a equivalent POLYGONS structure; if p is a list of GRID and MESH structures, then the result is a list of corresponding POLYGONS structures; if p is a PLOT3D structure, then the result is a list of POLYGONS structures corresponding to GRID and MESH structures in p.

$p≔\mathrm{plot3d}\left(\sin \left(xy\right)\,x=-1..1\,y=-1..1\,\mathrm{grid}=\left[3\,3\right]\right)\:$

$\mathrm{p2}≔\mathrm{convert}\left(p\,\mathrm{POLYGONS}\right)\:$

$m≔\mathrm{MESH}\left(\left[\left[\left[1\,2\,3\right]\,\left[4\,5\,6\right]\right]\,\left[\left[7\,8\,9\right]\,\left[1\,2\,3\right]\right]\right]\right)\:$

$\mathrm{convert}\left(\left[m\right]\,\mathrm{POLYGONS}\right)$

$\left[\mathrm{POLYGONS}\left(\left[\left[1\,2\,3\right]\,\left[4\,5\,6\right]\,\left[1\,2\,3\right]\,\left[7\,8\,9\right]\right]\right)\right]$