void initCornerPoints()  {
  Line l_temp;
  
  // base points, all at z=0;
  b1 = new Point();
  b2 = new Point();
  b3 = new Point();
  b4 = new Point();
  b1.setColor(0,255,0);
  b2.setColor(0,255,0);
  b3.setColor(0,255,0);
  b4.setColor(0,255,0);
  // top points
  t1 = new Point();
  t2 = new Point();
  t3 = new Point();
  t4 = new Point();
  t1.setColor(255,255,0);
  t2.setColor(255,255,0);
  t3.setColor(255,255,0);
  t4.setColor(255,255,0);
  
  // set x,y coords for base
  b1.x = 350;
  b1.y = fold.height - 225;
  b1.z = el_bline.height;
  b2.x = 385;
  l_temp = new Line(p1, b1);
  b2.y = l_temp.getY(b2.x);
  b2.z = el_bline.height;
  
  t1.x = b1.x+10;
  t1.y = b1.y - 50;
  t1.z = el_bline.height - 100;
  t2.x = b2.x - 5;
  l_temp = new Line(p1, t1, PLAN);
  t2.y = l_temp.getY(t2.x);
  l_temp = new Line(p1, t1, ELEVATION);
  t2.z = l_temp.getZ(t2.x);
  
  b3.x = 439;
  l_temp = new Line(p4, b2);
  b3.y = l_temp.getY(b3.x);
  b3.z = el_bline.height;
  b4.x = intersect(p2.x,p2.y, b3.x, b3.y,p3.x,p3.y, b1.x, b1.y);
  b4.y = setPt(b4.x, p2.x,p2.y, b3.x, b3.y);
  b4.z = el_bline.height;
  
  t3.x = b3.x +5;
  t3.y = setPt(t3.x, t2.x, t2.y, p4.x, p4.y);
  t3.z = setPt(t3.x, t2.x, t2.z, p4.x, p4.z);
  
  t4.x = intersect(p2.x,p2.y,t3.x,t3.y, p3.x,p3.y,t1.x,t1.y);
  t4.y = setPt(t4.x, p2.x,p2.y,t3.x,t3.y);
  t4.z = setPt(t4.x, p2.x, el_bline.height, t3.x, t3.z);
  
  b1.txtID = "B1";
  b2.txtID = "B2";
  b3.txtID = "B3";
  b4.txtID = "B4";
  
  t1.txtID = "T1";
  t2.txtID = "T2";
  t3.txtID = "T3";
  t4.txtID = "T4";
  
}