$m = $t->new(a=>[$x1,$y1,$z1], 
	     b=>[$x2,$y2,$z2], 
	     c=>[$x3,$y3,$z3]);

$t->link_edge(t1 => $n,
	      t2 => $m,
	      e1 => 'a',
	      e2 => 'c');