/// <summary>
/// Calculates the overlap between two <see cref="ColliderProjection"/>s.
/// <para>If at least one projection of two <see cref="ICollider"/>s does not overlap,
/// the colliders do not intersect.</para>
/// </summary>
/// <param name="a">The first <see cref="ColliderProjection"/>.</param>
/// <param name="b">The second <see cref="ColliderProjection"/>.</param>
/// <returns>The total overlap between the two projections.</returns>
public static float GetOverlap(ColliderProjection a, ColliderProjection b)
{
if ((a.Min <= b.Max) && (b.Min <= a.Max))
{
return(Math.Min(a.Max, b.Max) - Math.Max(a.Min, b.Min));
}
return(0);
}
bool TestPair(IPhysicsBody a, IPhysicsBody b, out Vector2 mtv)
{
Assert.Ref(a, b);
// collisions will be tested in a localized space, originating at the least common sector of both colliders
// (i think? this is easier than setting the origin at the collider vertex closest to 0,0)
WorldPoint origin = WorldPoint.LeastCommonSector(a.Position, b.Position);
Vector2 posA = a.Position.PixelDistance(origin);
Vector2 posB = b.Position.PixelDistance(origin);
// we're also returning the minimum translation vector
float minOverlap = float.MaxValue;
mtv = Vector2.Zero;
// test seperating axes
foreach (Vector2 axis in GetAllSeperatingAxes(a.Collider, b.Collider))
{
// project colliders on this seperating axis
ColliderProjection projA = a.Collider.Project(posA, axis);
ColliderProjection projB = b.Collider.Project(posB, axis);
// find the overlap. if there is none, we're not colliding and can get out now
float overlap = ColliderProjection.GetOverlap(projA, projB);
if (overlap > 0)
{
// otherwise, update the mtv if it's a smaller overlap than before
if (overlap < minOverlap)
{
minOverlap = overlap;
mtv = axis;
}
}
else
{
return(false);
}
}
// make sure mtv isn't negative
Vector2 diff = posA - posB;
if (diff.Dot(mtv) < 0)
{
mtv = -mtv;
}
// scale mtv by the smallest overlap, and we're done
mtv *= minOverlap;
return(true);
}