/// <summary>
/// Given a CircleEntity and the vertices and position of a 2D Polygon, checks if the circle and the polygon are overlapping
/// </summary>
/// <param name="circle"> The circle entity in question </param>
/// <param name="polyPosition"> The position of the polygon in question </param>
/// <param name="poly"> The world space position of the vertices of the polygon </param>
/// <param name="localPoly"> The local space position of the vertices of the polygon </param>
/// <returns></returns>
public static bool DetectCollision(CircleEntity circle, Vector polyPosition, Vector[] poly, Vector[] localPoly)
{
Vector relativeCirclePos = circle.position - polyPosition;
float seperation = -10000;
int face = -1234;
//Console.WriteLine("MOVEMNT TICK");
for (int i = 0; i < poly.Length; i++)
{
//get the normal
Vector normal = poly[i].GetNormal().Normalized();
Vector circleToPoint = relativeCirclePos - localPoly[i];
//dot the normal with the circle position
float currentSeperation = Vector.Dot(normal, circleToPoint);
//if result of dot is bigger than radius
if (currentSeperation >= circle.Radius)
{
//Console.WriteLine("NO COL");
return(false);
}
//return
//if its bigger than stored penetration
if (currentSeperation > seperation)
{
//store current face
//store current penetration
face = i;
seperation = currentSeperation;
}
}
Vector v1 = poly[face];
int secondIndex = face + 1 >= poly.Length ? 0 : face + 1;
Vector v2 = poly[secondIndex];
float v1Dot = Vector.Dot(circle.position - v1, v2 - v1);
float v2Dot = Vector.Dot(circle.position - v2, v1 - v2);
if (v1Dot <= 0)
{
if (Mathf.DistanceSquared(v1.x, v1.y, circle.position.x, circle.position.y) > circle.Radius * circle.Radius)
{
//Console.WriteLine("NO COL");
return(false);
}
}
else if (v2Dot <= 0)
{
if (Mathf.DistanceSquared(v2.x, v2.y, circle.position.x, circle.position.y) > circle.Radius * circle.Radius)
{
//Console.WriteLine("NO COL");
return(false);
}
}
return(true);
}
/// <summary>
/// Given a PolygonEntitiy and a Circle Entity, generates a manifold containing the information required to
/// resolve the collision (if there was one to begin with).
/// </summary>
public static Manifold GenerateManifold(PolygonEntity poly, CircleEntity circle)
{
Manifold Result;
Result.A = poly;
Result.B = circle;
Result.IsEmpty = false;
Result.ContactPoint = new List <Vector>();
Vector relativeCirclePos = circle.position - poly.position;
float seperation = -10000;
int face = -1234;
for (int i = 0; i < poly.GetVertices().Length; i++)
{
//get the normal
Vector normal = poly.GetFaceNormal(i).Normalized();
Vector circleToPoint = relativeCirclePos - poly.GetLocalSpaceVertices()[i];
//dot the normal with the circle position
float currentSeperation = Vector.Dot(normal, circleToPoint);
//if result of dot is bigger than radius
if (currentSeperation > circle.Radius)
{
return(GenerateEmptyManifold());
}
//return
//if its bigger than stored penetration
if (currentSeperation > seperation)
{
face = i;
seperation = currentSeperation;
}
}
Vector v1 = poly.GetVertices()[face];
int secondIndex = face + 1 >= poly.GetVertices().Length ? 0 : face + 1;
Vector v2 = poly.GetVertices()[secondIndex];
//if point is inside polygon
if (seperation < EPSILON)
{
//normal is negative face normal
Result.Normal = poly.GetFaceNormal(face).Normalized() * -1f;
Result.PenetrationDepth = circle.Radius;
Result.ContactPoint.Add(Result.Normal * circle.Radius + circle.position);
//penetration depth is radius
//contact point is -normal*radius + position
}
//determine which voronoi region the circle lies in
//dot with first point
float v1Dot = Vector.Dot(circle.position - v1, v2 - v1);
float v2Dot = Vector.Dot(circle.position - v2, v1 - v2);
Result.PenetrationDepth = circle.Radius - seperation;
//dot with second point
//penetration depth is radius-seperation
//if dot with first point is negative
if (v1Dot <= 0)
{
if (Mathf.DistanceSquared(v1.x, v1.y, circle.position.x, circle.position.y) > circle.Radius * circle.Radius)
{
return(GenerateEmptyManifold());
}
Result.Normal = (v1 - poly.position).Normalized();
Result.ContactPoint.Add(v1);
//normal is point-center
//contact point is point
}
else if (v2Dot <= 0)
{
if (Mathf.DistanceSquared(v2.x, v2.y, circle.position.x, circle.position.y) > circle.Radius * circle.Radius)
{
return(GenerateEmptyManifold());
}
Result.Normal = (v2 - poly.position).Normalized();
Result.ContactPoint.Add(v2);
}
else
{
Result.Normal = poly.GetFaceNormal(face).Normalized();
Result.ContactPoint.Add(Result.Normal * circle.Radius + circle.position);
}
return(Result);
}
