public static bool AABBvsAABB(AABB a, AABB b, ref Manifold m)
{
m.A = a;
m.B = b;
m.Normal = b.Position - a.Position;
//Calculate the extent on the X axis
float aExtent = (a.Right - a.Left) / 2;
float bExtent = (b.Right - b.Left) / 2;
//Find the X overlap
float xExtent = aExtent + bExtent - Math.Abs (m.Normal.X);
//SAT Test on X
if (xExtent > 0) {
//There was overlap on the X axis, now lets try to Y
aExtent = (a.Bottom - a.Top) / 2;
bExtent = (b.Bottom - b.Top) / 2;
//Calculate Y overlap
float yExtent = aExtent + bExtent - Math.Abs(m.Normal.Y);
//SAT Test on Y axis
if (yExtent > 0){
//Find which axis has the biggest penetration ;D
if (xExtent > yExtent){
// if(m.Normal.X < 0)
// m.Normal = -Vector2.UnitX;
// else
// m.Normal= Vector2.UnitX;
m.Normal = PhysicsMath.GetNormal(m.A.Position, m.B.Position);
m.PenetrationDepth = xExtent;
m.AreColliding = true;
return true;
}
else {
// if(m.Normal.Y < 0)
// m.Normal = -Vector2.UnitY;
// else
// m.Normal= Vector2.UnitY;
m.Normal = PhysicsMath.GetNormal(m.A.Position, m.B.Position);
m.PenetrationDepth = yExtent;
m.AreColliding = true;
return true;
}
}
}
return false;
}
public void Update(GameTime gameTime)
{
_aabb1.Update (gameTime);
_aabb2.Update (gameTime);
Manifold m = new Manifold ();
//bgcolor = Collision.TestAABBvsAABB(_aabb1, _aabb2, ref m) ? Color.Green : Color.Brown;
Collision.TestAABBvsAABB(_aabb1, _aabb2, ref m);
if (m.AreColliding) {
m = new Manifold();
Collision.TestAABBvsAABB (_aabb1, _aabb2, ref m);
Collision.ResolveCollision (m);
Collision.PositionalCorrection(m);
}
_aabb3.Update(gameTime);
_aabb4.Update(gameTime);
m = new Manifold();
Collision.TestAABBvsAABB(_aabb3, _aabb4, ref m);
if (m.AreColliding) {
m = new Manifold();
Collision.TestAABBvsAABB (_aabb3, _aabb4, ref m);
Collision.ResolveCollision (m);
Collision.PositionalCorrection(m);
}
_aabb5.Update(gameTime);
_aabb6.Update(gameTime);
m = new Manifold();
Collision.TestAABBvsAABB(_aabb5, _aabb6, ref m);
if (m.AreColliding) {
m = new Manifold();
Collision.TestAABBvsAABB (_aabb5, _aabb6, ref m);
Collision.ResolveCollision (m);
Collision.PositionalCorrection(m);
}
}
public static bool AABBvsCircle(AABB a, Circle b, ref Manifold m)
{
m.A = a;
m.B = b;
Vector2 n = b.Position - a.Position;
//Closest edge
Vector2 closest = m.Normal;
//Find extents for our AABB
float xExtent = (a.Right - a.Left) / 2;
float yExtent = (a.Right - a.Left) / 2;
closest.X = MathHelper.Clamp (-xExtent, xExtent, closest.X);
closest.Y = MathHelper.Clamp (-yExtent, yExtent, closest.Y);
//whether or not the circle is inside the aabb
bool inside = false;
if (n == closest) {
inside = true;
//Find closest edge
if (Math.Abs (n.X) > Math.Abs (n.Y)) {
// Clamp to closest extent
if (closest.X > 0)
closest.X = xExtent;
else
closest.X = -xExtent;
}
// Y axis is shorter
else {
// Clamp to closest extent
if (closest.Y > 0)
closest.Y = yExtent;
else
closest.Y = -yExtent;
}
}
m.Normal = n - closest;
float d = n.LengthSquared ();
float r = b.Radius;
//Early out if the circle's radius is shorter than the distance to the closest point
//and the circle isn't in the AABB.
if (d > r * r && !inside)
return false;
d = (float)Math.Sqrt (d);
if (inside) {
m.Normal = -PhysicsMath.GetNormal(a.Position, b.Position);
m.PenetrationDepth = r + d;
m.AreColliding = true;
return true;
}
else {
m.Normal = PhysicsMath.GetNormal(a.Position, b.Position);
m.PenetrationDepth = r + d;
m.AreColliding = true;
return true;
}
}
public static void ResolveCollision(Manifold m)
{
Vector2 relVelocity = m.B.Velocity - m.A.Velocity;
//Finds out if the objects are moving towards each other.
//We only need to resolve collisions that are moving towards, not away.
float velAlongNormal = PhysicsMath.DotProduct(relVelocity, m.Normal);
if (velAlongNormal > 0)
return;
float e = Math.Min(m.A.Restitution, m.B.Restitution);
float j = -(1 + e)*velAlongNormal;
j /= m.A.InvertedMass + m.B.InvertedMass;
Vector2 impulse = j*m.Normal;
m.A.Velocity -= m.A.InvertedMass*impulse;
m.B.Velocity += m.B.InvertedMass*impulse;
}
public static void PositionalCorrection(Manifold m)
{
const float percent = 0.2f;
const float slop = 0.01f;
Vector2 correction = Math.Max (m.PenetrationDepth - slop, 0.0f) / (m.A.InvertedMass + m.B.InvertedMass) * percent * m.Normal;
m.A.Position -= m.A.InvertedMass * correction;
m.B.Position += m.B.InvertedMass * correction;
}
public static bool CirclevsCircle(Circle a, Circle b, ref Manifold m)
{
m = new Manifold();
m.A = a;
m.B = b;
float collisionzone = a.Radius + b.Radius;
//collisionzone *= collisionzone;
float distance = 0f;
if (a.Position == b.Position)
distance = 0;
else if (a.Position.Y == b.Position.Y)
distance = Math.Abs(a.Position.X - b.Position.X);
else if (a.Position.X == b.Position.X)
distance = Math.Abs(a.Position.Y - b.Position.Y);
else
{
var lega = Math.Abs(a.Position.X - b.Position.X);
var legb = Math.Abs(a.Position.Y - b.Position.Y);
//lega *= lega;
//legb *= legb;
distance = lega + legb;
}
m.Normal = PhysicsMath.GetNormal(a.Position, b.Position);
bool collided = (collisionzone > distance);
if (collided)
{
//Perform an actual square root here
m.PenetrationDepth = a.Radius + b.Radius - (float)Math.Sqrt(distance);
}
else
m.PenetrationDepth = 0;
m.AreColliding = collided;
return collided;
}
