0 0 0 0 0
   0 0 0 0 0
   0 0 0 0 0
   0 0 0 0 0
   0 0 0 0 0
   pt1 = 2,1
   pt2 = 4,3
   pt3 = 0,3
   line(a,b):
     change = b/a
     ct = max(abs(change))
     for t = 0..ct inclusive:
       plot(a + change * t / ct)
   line(pt1,pt2)
   line(pt2,pt3)
   line(pt3,pt1)