拉斐尔动画中的新手问题

var c = paper.path('M '+p1.x+' '+p1.y+'L '+p2.x+' '+p2.y);

p1

p2

var p1x = 10;
var p1y = 10;

var p2x = 20;
var p2y = 20;

var t = setTimeout("timer()", 100);
var p = paper.path(...);

function timer()
{
   p1x++;
   p1y++;

   p.remove();
   p = paper.path(with new variables);

   if(p1x == p2x) clearTimeout(t);
}