4.3 clip

void clip(picture pic=currentpicture, path g, stroke=false,
          pen fillrule=currentpen);

Clip the current contents of picture pic to the region bounded by the path g, using fill rule fillrule (see fillrule). If stroke=true, the clipped portion is the same as the region that would be drawn with draw(pic,g,fillrule+zerowinding); in this case the path g need not be cyclic. For an illustration of picture clipping, see the first example in LaTeX usage.