/// <summary>
/// Applies position and velocity changes as a result of the collision.
/// </summary>
/// <param name="collider"></param>
/// <param name="collisionData"></param>
public static void ResolveCollision(CollisionData collisionData)
{
//return if there wan't a collision
if (!collisionData.DidCollide)
{
return;
}
Collider myCollider = collisionData.MyCollider;
Collider otherCollider = collisionData.OtherCollider;
float v1xf, v2xf;
//calculate restitution
float restitution = collisionData.Restitution;
//find the velocity of both objects in the direction of the collision
float v1xi = Vector2.Dot(myCollider.Body.Vel, collisionData.CollisionAngle);
float v2xi = Vector2.Dot(otherCollider.Body.Vel, collisionData.CollisionAngle);
//find time since collision
float timeSinceCollision;
if (v1xi - v2xi == 0)
{
timeSinceCollision = 0;
}
else
{
timeSinceCollision = collisionData.CollisionDepth / (v1xi - v2xi);
}
//Don't resolve the collision if the objects are moving away from each other
if (timeSinceCollision < 0)
{
return;
}
//limit how far objects can be pushed
if (timeSinceCollision > 1f / 30)
{
timeSinceCollision = 1f / 30;
}
//It's rewind time! (update positions)
myCollider.Body.Pos -= myCollider.Body.Vel * timeSinceCollision;
otherCollider.Body.Pos -= otherCollider.Body.Vel * timeSinceCollision;
//find the velocity of both objects perpendicular to the collision
Vector2 v1y = myCollider.body.Vel - v1xi * collisionData.CollisionAngle;
Vector2 v2y = otherCollider.Body.Vel - v2xi * collisionData.CollisionAngle;
//calculate the difference of the final velocities (I think?)
float gamma = restitution * (v1xi - v2xi);
if (myCollider.body.HasInfiniteMass)
{
//if both objects have infinite mass
if (otherCollider.body.HasInfiniteMass)
{
v1xf = v1xi;
v2xf = v2xi;
}
//if this object has infinite mass
else
{
v1xf = v1xi;
v2xf = gamma + v1xi;
}
}
//if the other object has infinite mass
else if (otherCollider.body.HasInfiniteMass)
{
v1xf = v2xi - gamma;
v2xf = v2xi;
}
//otherwise
else
{
//the big boy equation
v1xf = ((myCollider.Body.Mass * v1xi + otherCollider.Body.Mass * v2xi) / otherCollider.Body.Mass - gamma) / (1 + myCollider.Body.Mass / otherCollider.Body.Mass);
v2xf = gamma + v1xf;
}
//calculate and apply final velocities
myCollider.Body.Vel = v1xf * collisionData.CollisionAngle + v1y;
otherCollider.Body.Vel = v2xf * collisionData.CollisionAngle + v2y;
//move the objects after the collision
myCollider.Body.Pos += myCollider.Body.Vel * timeSinceCollision;
otherCollider.Body.Pos += otherCollider.Body.Vel * timeSinceCollision;
}
public override CollisionData CheckCollision(Collider collider)
{
//these values will be returned if there isn't a collision
bool didCollide = false;
float collisionDepth = 0;
Vector2 collisionAngle = new Vector2();
if (collider is CircleCollider)
{
CircleCollider circleCollider = (CircleCollider)collider;
//check for collision
Vector2 r = circleCollider.Body.Pos + circleCollider.Pos - (Body.Pos + Pos);
collisionDepth = (radius + circleCollider.Radius) - r.Length();
if (collisionDepth > 0)
{
didCollide = true;
//collision angle
r.Normalize();
collisionAngle = r;
}
}
else if (collider is RectangleCollider)
{
RectangleCollider rectangleCollider = (RectangleCollider)collider;
Vector2 myPos = Body.Pos + Pos;
Vector2 otherPos = rectangleCollider.Body.Pos + rectangleCollider.Pos;
//top left region
if (myPos.X < otherPos.X && myPos.Y < otherPos.Y)
{
Vector2 r = otherPos - myPos;
collisionDepth = radius - r.Length();
if (collisionDepth > 0)
{
didCollide = true;
r.Normalize();
collisionAngle = r;
}
}
//top right region
else if (myPos.X > otherPos.X + rectangleCollider.Dimensions.X && myPos.Y < otherPos.Y)
{
Vector2 r = otherPos + new Vector2(rectangleCollider.Dimensions.X, 0) - myPos;
collisionDepth = radius - r.Length();
if (collisionDepth > 0)
{
didCollide = true;
r.Normalize();
collisionAngle = r;
}
}
//bottom right region
else if (myPos.X > otherPos.X + rectangleCollider.Dimensions.X && myPos.Y > otherPos.Y + rectangleCollider.Dimensions.Y)
{
Vector2 r = otherPos + rectangleCollider.Dimensions - myPos;
collisionDepth = radius - r.Length();
if (collisionDepth > 0)
{
didCollide = true;
r.Normalize();
collisionAngle = r;
}
}
//bottom left region
else if (myPos.X < otherPos.X && myPos.Y > otherPos.Y + rectangleCollider.Dimensions.Y)
{
Vector2 r = otherPos + new Vector2(0, rectangleCollider.Dimensions.Y) - myPos;
collisionDepth = radius - r.Length();
if (collisionDepth > 0)
{
didCollide = true;
r.Normalize();
collisionAngle = r;
}
}
//if it isn't in any of those regions, it's basically a square
else
{
Collider rectangularHull = new RectangleCollider(Body, CollisionGroup, new Vector2(Pos.X - Radius, pos.Y - Radius), new Vector2(radius * 2, radius * 2), OnCollision);
CollisionData collisionData = rectangularHull.CheckCollision(rectangleCollider);
didCollide = collisionData.DidCollide;
collisionDepth = collisionData.CollisionDepth;
collisionAngle = collisionData.CollisionAngle;
}
}
return(new CollisionData(didCollide, collisionDepth, collisionAngle, this, collider));
}
public override CollisionData CheckCollision(Collider collider)
{
//these values will be returned if there isn't a collision
bool didCollide = false;
float collisionDepth = 0;
Vector2 collisionAngle = new Vector2();
if (collider is RectangleCollider)
{
RectangleCollider rectangleCollider = (RectangleCollider)collider;
Vector2 myPos = Body.Pos + Pos;
Vector2 otherPos = rectangleCollider.Body.Pos + rectangleCollider.Pos;
//check for collision
if (myPos.Y < otherPos.Y + rectangleCollider.Dimensions.Y && myPos.Y + Dimensions.Y > otherPos.Y && myPos.X < otherPos.X + rectangleCollider.Dimensions.X && myPos.X + Dimensions.X > otherPos.X)
{
didCollide = true;
//check if it's a vertical collision
Vector2 r = otherPos - myPos;
float collisionAngleConstant = (Dimensions.Y + rectangleCollider.Dimensions.Y) / (Dimensions.X + rectangleCollider.Dimensions.X);
if (Math.Abs(r.Y) >= collisionAngleConstant * Math.Abs(r.X))
{
if (myPos.Y < otherPos.Y)
{
collisionAngle = new Vector2(0, 1);
//collision depth
collisionDepth = myPos.Y + Dimensions.Y - otherPos.Y;
}
else
{
collisionAngle = new Vector2(0, -1);
//collision depth
collisionDepth = otherPos.Y + rectangleCollider.Dimensions.Y - myPos.Y;
}
}
//if it's a horizontal collision
else
{
if (myPos.X < otherPos.X)
{
collisionAngle = new Vector2(1, 0);
//collision depth
collisionDepth = myPos.X + Dimensions.X - otherPos.X;
}
else
{
collisionAngle = new Vector2(-1, 0);
//collision depth
collisionDepth = otherPos.X + rectangleCollider.Dimensions.X - myPos.X;
}
}
}
}
else if (collider is CircleCollider)
{
CollisionData collisionData = collider.CheckCollision(this);
didCollide = collisionData.DidCollide;
collisionDepth = collisionData.CollisionDepth;
collisionAngle = -collisionData.CollisionAngle;
}
return(new CollisionData(didCollide, collisionDepth, collisionAngle, this, collider));
}
