/// <summary>
/// Performs an AABB AABB collision check.
/// </summary>
/// <param name="a">First AABB.</param>
/// <param name="b">Second AABB.</param>
/// <returns></returns>
private static Collision AABBAABB(BoundingBox a, BoundingBox b)
{
// Minimum Translation Vector
// ==========================
float minimumTranslationVectorDistance = float.MaxValue; // Set current minimum distance (max float value so next value is always less)
Vector3 minimumTranslationVectorAxis = new Vector3(); // Axis along which to travel with the minimum distance
var containment = a.Contains(b);
var normal = Vector3.Zero;
float penetrationDepth = 0f;
if (containment == ContainmentType.Disjoint)
{
return(new Collision(false, normal, penetrationDepth));
}
// Axes of potential separation
// ============================
// - Each shape must be projected on these axes to test for intersection:
//
// (1, 0, 0) A0 (= B0) [X Axis]
// (0, 1, 0) A1 (= B1) [Y Axis]
// (0, 0, 1) A1 (= B2) [Z Axis]
// [X Axis]
if (!SAT(Vector3.Right, a.Min.X, a.Max.X, b.Min.X, b.Max.X, ref minimumTranslationVectorAxis, ref minimumTranslationVectorDistance))
{
return(new Collision(false, normal, penetrationDepth));
}
// [Y Axis]
if (!SAT(Vector3.Up, a.Min.Y, a.Max.Y, b.Min.Y, b.Max.Y, ref minimumTranslationVectorAxis, ref minimumTranslationVectorDistance))
{
return(new Collision(false, normal, penetrationDepth));
}
// [Z Axis]
if (!SAT(Vector3.Back, a.Min.Z, a.Max.Z, b.Min.Z, b.Max.Z, ref minimumTranslationVectorAxis, ref minimumTranslationVectorDistance))
{
return(new Collision(false, normal, penetrationDepth));
}
// Calculate Minimum Translation Vector (MTV) [normal * penetration]
normal = Vector3.Normalize(minimumTranslationVectorAxis);
// Multiply the penetration depth by itself plus a small increment
// When the penetration is resolved using MTV, it will no longer intersect
penetrationDepth = MathF.Sqrt(minimumTranslationVectorDistance) * 1.001f;
return(new Collision(true, normal, penetrationDepth));
}
