#### 10.9.25 Section

• Section( <plane>, <polyhedron> )
• Description: that macro cuts a <polyhedron> with a <plane>. The plane must be in the form: $\left[S,u\right]$, this is the plane passing through the point $S$ and normal to the vector $u$. The macro determines the section of the polyhedron by that plane, and the part of the polyhedron that is in the half-space containing the vector $u$, is kept and returned by the macro in the form of a polyhedron (facets list).
• Exemple(s): section of a cube:

 \begin{texgraph}[name=Section, export=pgf]   view(-2,3,-2.5,3), Marges(0,0,0,0), size(7.5),   cube:=Parallelep(Origin,3*vecI,3*vecJ,3*vecK),   plan:=[M(3,0,0),-vecI-vecK/2],   S:=Section(plan, cube), FillStyle:=full,   FillColor:=firebrick, HideWidth:=8,   DrawPoly(S,4)   \end{texgraph}

Section