public static bool Intersect(Circle c, Box b, out SIntersectionInfo collInfo)
{
collInfo = new SIntersectionInfo();
//Special case: Our center is inside the box, this is the easiest case to detect, hardest to handle
if (PointInBox(b, c.Center))
{
//CHEAT: project our center's circle onto every edge
// pick the closest one
// say that we interesected there (not accurate, can create bugs for fast moving objects or small circles)
//Each edge of the box
Edge[] edges =
{
new Edge(b.tlCorner, b.trCorner),
new Edge(b.trCorner, b.brCorner),
new Edge(b.brCorner, b.blCorner),
new Edge(b.blCorner, b.tlCorner)
};
float smallestDistance = float.MaxValue;
foreach (Edge e in edges)
{
Vector2 proj = (Vector2.Dot(c.Center - e.P1, e.Dir) / Vector2.Dot(e.Dir, e.Dir)) * e.Dir;
float dist = ((c.Center - e.P1) - proj).magnitude;
//Each time we find an edge closer to our center, set ourselves to intersect there
if (dist < smallestDistance)
{
smallestDistance = dist;
collInfo.intersectionPoint = proj + e.P1;
collInfo.intersectionDepth = (c.Center - collInfo.intersectionPoint).magnitude;
collInfo.intersectionNormal = new Vector2(-e.Dir.y, e.Dir.x).normalized;
}
}
return(true);
}
//Otherwise there may be an intersection despite our center not being inside
else
{
return(LineIntersectCircle(c, new Edge(b.tlCorner, b.trCorner), out collInfo) ||
LineIntersectCircle(c, new Edge(b.trCorner, b.brCorner), out collInfo) ||
LineIntersectCircle(c, new Edge(b.brCorner, b.blCorner), out collInfo) ||
LineIntersectCircle(c, new Edge(b.blCorner, b.tlCorner), out collInfo));
}
}
public static bool LineIntersectCircle(Circle c, Edge e, out SIntersectionInfo collInfo)
{
float ratioProj = (Vector2.Dot(c.Center - e.P1, e.Dir) / Vector2.Dot(e.Dir, e.Dir));
collInfo = new SIntersectionInfo();
//Verify if our projected point lies on the actual edge, aka whether it maps to a length between 0 and 1 of the edge
if (ratioProj >= 0.0f && ratioProj <= 1.0f)
{
//Get the perpendicular of the projection triangle formed by the center and the edge starting at P1
Vector2 perp = (c.Center - e.P1) - (ratioProj * e.Dir);
//Then return whether the distance between the center and the edge is smaller than the radius
if (perp.magnitude <= c.Radius)
{
//Set the collision depth and the collision point to be where the edge of the circle is past the edge
collInfo.intersectionDepth = c.Radius - perp.magnitude;
collInfo.intersectionPoint = c.Center - perp;
collInfo.intersectionNormal = new Vector2(-e.Dir.y, e.Dir.x).normalized;
return(true);
}
}
else
{
//If our projection isn't between the two points, check whether the edge points are within the radius of the center
//The collision will occur at the edge points if there is one
if ((c.Center - e.P1).magnitude <= c.Radius)
{
collInfo.intersectionDepth = c.Radius - (c.Center - e.P1).magnitude;
collInfo.intersectionPoint = e.P1;
collInfo.intersectionNormal = new Vector2(-e.Dir.y, e.Dir.x).normalized;
return(true);
}
else if ((c.Center - e.P2).magnitude <= c.Radius)
{
collInfo.intersectionDepth = c.Radius - (c.Center - e.P2).magnitude;
collInfo.intersectionPoint = e.P2;
collInfo.intersectionNormal = new Vector2(-e.Dir.y, e.Dir.x).normalized;
return(true);
}
}
return(false);
}
//Test whether circle 1 intersects circle 2
public static bool Intersect(Circle c1, Circle c2, out SIntersectionInfo collision)
{
float distanceCenter = (c1.Center - c2.Center).magnitude;
collision = new SIntersectionInfo();
//Calculate whether the distance between centers is smaller than radius sum (consider edges touching a collision)
if (distanceCenter <= c1.Radius + c2.Radius)
{
collision.intersectionDepth = c1.Radius + c2.Radius - distanceCenter;
//Set the intersection point on the edge of the second circle towards the first circle center
collision.intersectionPoint = c2.Center + (c1.Center - c2.Center).normalized * c2.Radius;
collision.intersectionNormal = (c1.Center - c2.Center).normalized;
return(true);
}
else
{
return(false);
}
}
