Artificial Intelligence in Video Games: Towards a Unified Framework

Algorithm 7

Dodging a straight line projectile. This function assumes that the projectile is not penetrating.

void  dodge_projectile(Unit  u, Projectile  p)

{

 //Create a ray for the projectile course

 Ray r(p->position(), p->velocity());

 //Get a list of objects intersecting the ray

 ObjectList is = intersection(r, p->radius());

 //Only dodge if u is the first object to intersect the ray

 if  (is.front() == u)

 {

  //Is u exactly on the projectile course?

  if  (r.passthru(u->position()))

  {

   //Move perpendicularly by a distance equal to the sum of bounding radiuses

   u->move(u->position() + r.normal()(p->radius() + u->radius()));

   return;

  }

  //Project the unit position on the projectile course

  Vector pr = r->project(u->position());

  //Get a normal to the projectile course with a norm equal to the distance between

   the unit position and its projection

  Vector mv = u->position() − pr;

  //Rescale it to the width of the intersection

  mv  = (p->radius() −   (mv.norm() −   u->radius()))/mv.norm();

  //Follow the normal to avoid collision

  u->move(u->position() + mv);

 }

}