// This function calculates Circle to OBB collisions
public static CollisionInfo CircleToABBCollision(CollisionHull2D a, CollisionHull2D b)
{
// Find the closest point to the circle from the AABB
Vector2 closestPointToCircle = new Vector2(Math.Max(b.GetMinimumCorner().x, Math.Min(a.GetPosition().x, b.GetMaximumCorner().x)), Math.Max(b.GetMinimumCorner().y, Math.Min(a.GetPosition().y, b.GetMaximumCorner().y)));
// Get the distance between the closest point and the circle's position
Vector2 distance = a.GetPosition() - closestPointToCircle;
float distanceSquared = Vector2.Dot(distance, distance);
// Calculate the penetration
float penetration = a.GetDimensions().x - Mathf.Sqrt(distanceSquared);
// Is the penetration a positive value
if (penetration > 0)
{
// If yes, then inform the parents of the complex shape object (if applicable)
ReportCollisionToParent(a, b);
}
else
{
// If no, return nothing
return(null);
}
// Return full details of the Collision list if the two collide
return(new CollisionInfo(a, b, penetration));
}
// This function computes AABB to AABB collisions
public static CollisionInfo AABBToAABBCollision(CollisionHull2D a, CollisionHull2D b)
{
// Get the penetration values for both axes
float penetration = 0.0f;
// Calculate half extents along x axis for each object
float a_extent = a.GetDimensions().x;
float b_extent = b.GetDimensions().x;
// Get the distance between a and b
Vector2 n = (b.GetPosition() - a.GetPosition());
n = new Vector2(Mathf.Abs(n.x), Mathf.Abs(n.y));
// Calculate overlap on x axis
float x_overlap = a_extent + b_extent - Mathf.Abs(n.x);
// SAT test on x axis
if (x_overlap > 0)
{
// Calculate half extents along x axis for each object
a_extent = a.GetDimensions().y;
b_extent = b.GetDimensions().y;
// Calculate overlap on y axis
float y_overlap = a_extent + b_extent - Mathf.Abs(n.y);
// SAT test on y axis
if (y_overlap > 0)
{
// Find out which axis is axis of least penetration
if (x_overlap > y_overlap)
{
// If it is Y, then return Y's overlap
penetration = y_overlap;
}
else
{
// If it is Y, then return X's overlap
penetration = x_overlap;
}
}
}
// Do the two checks pass?
if (penetration > 0)
{
// If yes, then inform the parents of the complex shape object (if applicable)
ReportCollisionToParent(a, b);
}
else
{
// If no, return nothing
return(null);
}
// Return full details of the Collision list if the two collide
return(new CollisionInfo(a, b, penetration));
}
// This function gets the seperating velocity of two particles
public static float CalculateSeparatingVelocity(CollisionHull2D shapeA, CollisionHull2D shapeB)
{
// Find all required values for calculation
Vector2 differenceOfVelocity = (shapeA.gameObject.GetComponent <Particle2D>().velocity - shapeB.gameObject.GetComponent <Particle2D>().velocity) * -1;
Vector2 differenceOfPosition = (shapeA.GetPosition() - shapeB.GetPosition()).normalized;
// Return the dot product of both velocity and position
return(Vector2.Dot(differenceOfVelocity, differenceOfPosition));
}
// This function gets the seperating velocity of two particles
public static float CalculateSeparatingVelocity(CollisionHull2D shapeA, CollisionHull2D shapeB)
{
// Find all required values for calculation
Vector2 differenceOfVelocity = (shapeA.gameObject.GetComponent <Particle2D>().velocity - shapeB.gameObject.GetComponent <Particle2D>().velocity) * -1;
Vector2 differenceOfPosition = (shapeA.GetPosition() - shapeB.GetPosition()).normalized;
// Return the dot product of both velocity and position
// Since we are dealing with planes, there is no reason to check the X axis
return(differenceOfPosition.y * differenceOfVelocity.y * COLLISION_AMPLIFIER);
}
// This function intializes the collision info class based on given information
public CollisionInfo(CollisionHull2D _a, CollisionHull2D _b, float _penetration)
{
// Is collision A's collision type have less priority to collision B?
if (_a.collisionType > _b.collisionType)
{
// If yes, then switch their priorities
a = _b;
b = _a;
}
else
{
// If no, then keep them as so
a = _a;
b = _b;
}
// Based on collision hulls, calculate the rest of the values
separatingVelocity = CollisionResolution.CalculateSeparatingVelocity(a, b);
normal = (b.GetPosition() - a.GetPosition()).normalized;
penetration = _penetration;
}
// This function computes circle to circle collisions
public static CollisionInfo CircleToCircleCollision(CollisionHull2D a, CollisionHull2D b)
{
// Calculate the distance between both colliders
Vector2 distance = a.GetPosition() - b.GetPosition();
float penetration = a.GetDimensions().x + b.GetDimensions().x *(a.GetDimensions().x + b.GetDimensions().x) - Vector2.Dot(distance, distance);
// Are the Radii less than or equal to the distance between both circles?
if (penetration > 0)
{
// If yes, then inform the parents of the complex shape object (if applicable)
ReportCollisionToParent(a, b);
}
else
{
// If no, return nothing
return(null);
}
// Return result
return(new CollisionInfo(a, b, penetration));
}
// This function calculate Circle to ABB collisions
public static CollisionInfo CircleToOBBCollision(CollisionHull2D a, CollisionHull2D b)
{
Vector2 closestPointToCircle = new Vector2(Math.Max(b.GetMinimumCorner().x, Math.Min(a.GetPosition().x, b.GetMaximumCorner().x)), Math.Max(b.GetMinimumCorner().y, Math.Min(a.GetPosition().y, b.GetMaximumCorner().y)));
Vector2 distance = a.GetPosition() - closestPointToCircle;
float distanceSquared = Vector2.Dot(distance, distance);
float penetration = a.GetDimensions().x - Mathf.Sqrt(distanceSquared);
// Does the check pass?
if (penetration > 0)
{
// If yes, then inform the parents of the complex shape object (if applicable)
ReportCollisionToParent(a, b);
}
else
{
// If no, return nothing
return(null);
}
// Return full details of the Collision list if the two collide
return(new CollisionInfo(a, b, penetration));
}
// This function checks for a collision between two objects by projecting onto a specific axis
public static float CheckOBBAxis(CollisionHull2D shapeA, CollisionHull2D shapeB, Vector2 rotationAxis)
{
// Create a list of all points from the OBB hull for shape A
List <Vector2> shapeAPoints = new List <Vector2>();
shapeAPoints.Add(new Vector2(shapeA.GetPosition().x + shapeA.GetDimensions().x, shapeA.GetPosition().y + shapeA.GetDimensions().y));
shapeAPoints.Add(new Vector2(shapeA.GetPosition().x - shapeA.GetDimensions().x, shapeA.GetPosition().y - shapeA.GetDimensions().y));
shapeAPoints.Add(new Vector2(shapeA.GetPosition().x - shapeA.GetDimensions().x, shapeA.GetPosition().y + shapeA.GetDimensions().y));
shapeAPoints.Add(new Vector2(shapeA.GetPosition().x + shapeA.GetDimensions().x, shapeA.GetPosition().y - shapeA.GetDimensions().y));
// Create a list of all points from the OBB hull for shape B
List <Vector2> shapeBPoints = new List <Vector2>();
shapeBPoints.Add(new Vector2(shapeB.GetPosition().x + shapeB.GetDimensions().x, shapeB.GetPosition().y + shapeB.GetDimensions().y));
shapeBPoints.Add(new Vector2(shapeB.GetPosition().x - shapeB.GetDimensions().x, shapeB.GetPosition().y - shapeB.GetDimensions().y));
shapeBPoints.Add(new Vector2(shapeB.GetPosition().x - shapeB.GetDimensions().x, shapeB.GetPosition().y + shapeB.GetDimensions().y));
shapeBPoints.Add(new Vector2(shapeB.GetPosition().x + shapeB.GetDimensions().x, shapeB.GetPosition().y - shapeB.GetDimensions().y));
// Initialized shape minimums and maximums
float shapeAMin = Mathf.Infinity;
float shapeAMax = -Mathf.Infinity;
float shapeBMin = Mathf.Infinity;
float shapeBMax = -Mathf.Infinity;
// Set the total minimum and maximums
float totalMin;
float totalMax;
// Initialize all points for axis checks
for (int i = 0; i < shapeAPoints.Count; i++)
{
// Rotate original point
shapeAPoints[i] = new Vector2(Mathf.Cos(shapeA.GetRotation()) * (shapeAPoints[i].x - shapeA.GetPosition().x) - Mathf.Sin(shapeA.GetRotation()) * (shapeAPoints[i].y - shapeA.GetPosition().y) + shapeA.GetPosition().x,
Mathf.Sin(shapeA.GetRotation()) * (shapeAPoints[i].x - shapeA.GetPosition().x) + Mathf.Cos(shapeA.GetRotation()) * (shapeAPoints[i].y - shapeA.GetPosition().y) + shapeA.GetPosition().y);
// Project point
float temp = Vector2.Dot(shapeAPoints[i], rotationAxis);
// Is the point less than the minimum?
if (temp < shapeAMin)
{
// If yes, set it to the new minimum
shapeAMin = temp;
}
// Is the point greater than the maximum?
if (temp > shapeAMax)
{
// If yes, set it to the new maximum
shapeAMax = temp;
}
// Rotate original point
shapeBPoints[i] = new Vector2(Mathf.Cos(shapeB.GetRotation()) * (shapeBPoints[i].x - shapeB.GetPosition().x) - Mathf.Sin(shapeB.GetRotation()) * (shapeBPoints[i].y - shapeB.GetPosition().y) + shapeB.GetPosition().x,
Mathf.Sin(shapeB.GetRotation()) * (shapeBPoints[i].x - shapeB.GetPosition().x) + Mathf.Cos(shapeB.GetRotation()) * (shapeBPoints[i].y - shapeB.GetPosition().y) + shapeB.GetPosition().y);
// Project point
temp = Vector2.Dot(shapeBPoints[i], rotationAxis);
// Is the point less than the minimum?
if (temp < shapeBMin)
{
// If yes, set it to the new minimum
shapeBMin = temp;
}
// Is the point greater than the maximum
if (temp > shapeBMax)
{
// If yes, set it to the new maximum
shapeBMax = temp;
}
}
// Is the B shape min greater than the A shape maximum
if (shapeBMin > shapeAMin)
{
// If yes, set A to the new minimum
totalMin = shapeAMin;
}
else
{
// If no, set B to the new minimum
totalMin = shapeBMin;
}
// Is the A shape maximum greater than the B shape maximum
if (shapeBMax < shapeAMax)
{
// If yes, set A to the new maximum
totalMax = shapeAMax;
}
else
{
// If no, set B to the new maximum
totalMax = shapeBMax;
}
// Do axis checks
bool axisCheck = shapeAMin <= shapeBMax && shapeBMin <= shapeAMax;
// Does the check pass?
if (axisCheck)
{
// If yes, then return the penetration
return(totalMin - totalMax);
}
else
{
// If no, return nothing
return(Mathf.Infinity);
}
}
