static bool Collide(AABB a, AABB b)
{
// If either bounding box is separated along any axis, we can be sure that there is no collision
if (a.Max.X < b.Min.X || a.Min.X > b.Max.X) return false;
if (a.Max.Y < b.Min.Y || a.Min.Y > b.Max.Y) return false;
return true;
}
bool Collide(ref Manifold m, AABB a, AABB b)
{
Vector2 n = b.Position - a.Position;
float aExtent = (a.Max.X - a.Min.X) / 2;
float bExtent = (b.Max.X - b.Min.X) / 2;
float xOverlap = aExtent + bExtent - Math.Abs(n.X);
if (xOverlap > 0) {
aExtent = (a.Max.Y - a.Min.Y) / 2;
bExtent = (b.Max.Y - b.Min.Y) / 2;
float yOverlap = aExtent + bExtent - Math.Abs(n.Y);
if (yOverlap > 0) {
if (xOverlap > yOverlap) {
if (n.X < 0) {
m.Normal = new Vector2(-1, 0);
} else {
m.Normal = new Vector2(0, 0);
}
m.Penetration = xOverlap;
return true;
} else {
// Point toward B knowing that n points from A to B
if (n.Y < 0) {
m.Normal = new Vector2(0, -1);
} else {
m.Normal = new Vector2(0, 1);
}
m.Penetration = yOverlap;
return true;
}
}
}
return false;
}
bool Collide(Manifold m, AABB a, Circle b)
{
// Vector from A to B
Vector2 n = b.Position - a.Position;
// Closest point on A to center of B
Vector2 closest = n;
// Calculate half extents along each axis
float x_extent = (a.Max.X - a.Min.X) / 2f;
float y_extent = (a.Max.Y - a.Min.Y) / 2f;
// Clamp point to edges of the AABB
closest = Vector2.Clamp(closest, new Vector2(-x_extent, -y_extent), new Vector2(x_extent, y_extent));
bool inside = false;
// Circle is inside the AABB, so we need to clamp the circle's center
// to the closest edge
if (n == closest) {
inside = true;
// Find closest axis
if (Math.Abs(n.X) > Math.Abs(n.Y)) {
// Clamp to closest extent
if (closest.X > 0)
closest.X = x_extent;
else
closest.X = -x_extent;
}
// y axis is shorter
else {
// Clamp to closest extent
if (closest.Y > 0)
closest.Y = y_extent;
else
closest.Y = -y_extent;
}
}
Vector2 normal = n - closest;
double d = normal.LengthSquared();
float r = b.Radius;
// Early out of the radius is shorter than distance to closest point and
// Circle not inside the AABB
if (d > r * r && !inside)
return false;
// Avoided sqrt until we needed
d = Math.Sqrt(d);
// Collision normal needs to be flipped to point outside if circle was
// inside the AABB
if (inside) {
m.Normal = -n;
m.Penetration = r + (float)d;
} else {
m.Normal = n;
m.Penetration = r + (float)d;
}
return true;
}