/// <summary>
/// Do a narrow phase collision check between two shapes by using SAT (Separating Axis Theorem).
/// If a collision has occurred, get the MTV (Minimum Translation Vector) of the two intersecting shapes.
/// </summary>
/// <param name="s1">The first shape to check.</param>
/// <param name="s2">The second shape to check.</param>
/// <returns>The MTV of the intersection.</returns>
public CollisionData NarrowPhase(Shape s1, Shape s2)
{
// The minimum amount of overlap. Start real high.
float overlap = float.MaxValue;
//The collision data.
CollisionData data = new CollisionData(s1, s2);
// The smallest axis found.
Vector2 smallest = Vector2.Zero;
try
{
// Get the axes of both bodies.
Vector2[][] axes = new Vector2[][] { s1.GetAxes(), s2.GetAxes() };
// Iterate over the axes of both bodies.
foreach (Vector2[] v in axes)
{
// Iterate over both bodies' axes.
foreach (Vector2 a in v)
{
// Project both bodies onto the axis.
Vector2 p1 = s1.Project(a);
Vector2 p2 = s2.Project(a);
// Get the overlap.
float o = Calculator.GetOverlap(p1, p2);
// Do the projections overlap?
if (o == -1)
{
// We can guarantee that the shapes do not overlap.
return data;
}
else
{
// Check for minimum.
if (o < overlap)
{
// Store the minimum overlap and the axis it was projected upon. Make sure that the separation vector is pointing the right way.
overlap = o;
smallest = a;
}
}
}
}
}
catch (Exception e)
{
Console.WriteLine(this + ": Narrow Phase Error. (" + e + ")");
}
// We now know that every axis had an overlap on it, which means we can guarantee an intersection between the bodies.
data.HasCollision = true;
data.Axis = smallest;
data.Overlap = overlap;
//Return the collision data.
return data;
}
