5.5.3 Mixing 2D and 3D graphics

When one uses 3D plotting function, default graphic boundaries are fixed, but in $R^3$. If one wants to use graphic primitives to add informations on 3D graphics, the geom3d function can be used to convert 3D coordinates to 2D-graphics coordinates. The figure  5.10 illustrates this feature.

xinit('d7-10.ps');
   r=(%pi):-0.01:0;x=r.*cos(10*r);y=r.*sin(10*r);
   function z=surf(x,y),z=sin(x)*cos(y);endfunction
   t=%pi*(-10:10)/10;
   fplot3d(t,t,surf,theta=35,alpha=45,leg="X@Y@Z",flag=[-3,2,3]);
   z=sin(x).*cos(y);
   [x1,y1]=geom3d(x,y,z);
   xpoly(x1,y1,"lines");
   [x1,y1]=geom3d([0,0],[0,0],[5,0]);
   xsegs(x1,y1);
   xstring(x1(1),y1(1),' The point (0,0,0)');

Figure 5.10: 2D and 3D plot