// a triangle that can remember if it has been clicked, and can shrink on request
class Triangle {

  Vector3d a,b,c;
  boolean clicked = false;

  Triangle() {
    this.a = new Vector3d();
    this.b = new Vector3d();
    this.c = new Vector3d();
  }
    
  // NB: will never stop shrinking, which is silly.
  void shrink() {
    Vector3d av = new Vector3d((a.x+b.x+c.x)/3.0,(a.y+b.y+c.y)/3.0,(a.z+b.z+c.z)/3.0);
    a.x += (av.x-a.x)/5.0;
    a.y += (av.y-a.y)/5.0;
    a.z += (av.z-a.z)/5.0;
    b.x += (av.x-b.x)/5.0;
    b.y += (av.y-b.y)/5.0;
    b.z += (av.z-b.z)/5.0;
    c.x += (av.x-c.x)/5.0;
    c.y += (av.y-c.y)/5.0;
    c.z += (av.z-c.z)/5.0;
  }

}