internal Pair <Vector2, Vector2> computeTangentsPoints(Agent observer, Agent agent)
{
// First element of the pair = left tangent
// Second element of the pair = right tangent
Pair <Vector2, Vector2> toReturn = new Pair <Vector2, Vector2>();
Vector2 centers = agent.position_ - observer.position_;
Vector2 r1a = Vector2.normalize(Vector2.rotation(centers, (float)-Math.PI / 2)) * observer.radius_;
Vector2 r1b = Vector2.normalize(Vector2.rotation(centers, (float)Math.PI / 2)) * observer.radius_;
// Compute intersection points between radius and circle
// Right one
Vector2 h1a = observer.position_ + r1a;
// Left one
Vector2 h1b = observer.position_ + r1b;
// If the radius is the same, tangents points are perpendicular to centers vector
if (Math.Abs(observer.radius_ - agent.radius_) < RVO_EPSILON)
{
toReturn.First = h1a;
toReturn.Second = h1b;
}
else
{
Vector2 r2a = Vector2.normalize(Vector2.rotation(centers, (float)-Math.PI / 2)) * agent.radius_;
Vector2 r2b = Vector2.normalize(Vector2.rotation(centers, (float)Math.PI / 2)) * agent.radius_;
Vector2 h2a = agent.position_ + r2a;
Vector2 h2b = agent.position_ + r2b;
// If tangents are parallel, radius are the same, i.e. there is no intersection point.
if (Math.Abs(Vector2.det(h1a - h2a, h1b - h2b)) < RVO_EPSILON)
{
Console.Write("Problem while computing tangent points\n SHALL NOT HAPPEN !!! \n");
toReturn.First = h1a;
toReturn.Second = h1b;
}
else
{
Vector2 intersectionPoint = Vector2.intersectOf2Lines(h1a, h2a, h1b, h2b);
// Equivalent to :
Vector2 circleCenter = (intersectionPoint + observer.position_) / 2;
toReturn = Vector2.intersectOf2Circles(circleCenter, Vector2.abs(circleCenter - observer.position_), observer.position_, observer.radius_);
// Test angles to know which one is right & which one is left
if (Vector2.isOnTheLeftSide(toReturn.First - observer.position_, centers))
{
Vector2 temp = toReturn.First;
toReturn.First = toReturn.Second;
toReturn.Second = temp;
}
}
}
return(toReturn);
}
