/// <summary>
/// Returns whether a line intersects a circle and the points at which it intersects
/// </summary>
LineIntersectCircleResult TestLineIntersectsCircle(Vector2 lineStart, Vector2 lineEnd, Vector2 circleCenter, float circleRadius)
{
LineIntersectCircleResult ret = new LineIntersectCircleResult();
float x1 = lineStart.X - circleCenter.X;
float x2 = lineEnd.X - circleCenter.X;
float y1 = lineStart.Y - circleCenter.Y;
float y2 = lineEnd.Y - circleCenter.Y;
float a = (float)Math.Pow(y2 - y1, 2) + (float)Math.Pow(x2 - x1, 2);
float b = 2 * (x1 * (x2 - x1) + y1 * (y2 - y1));
float c = x1 * x1 + y1 * y1 - circleRadius * circleRadius;
//t = (-b +- Sqrt(b^2 - 4ac)) / (2a)
float D = b * b - 4 * a * c;
if (D < 0)
{
return(ret); //no intersect
}
float sqD = (float)Math.Sqrt(D);
ret.T1 = (-b + sqD) / (2 * a);
ret.T2 = (-b - sqD) / (2 * a);
ret.Intersect1 = lineStart + (lineEnd - lineStart) * ret.T1;
ret.Intersect2 = lineStart + (lineEnd - lineStart) * ret.T2;
ret.Intersects = true;
return(ret);
}
/// <summary>
/// Tests whether any of the vertices of this polygon collide with a specified line segment when this polygon
/// is rotated
/// </summary>
/// <param name="moveBy"></param>
/// <param name="lineStart"></param>
/// <param name="lineEnd"></param>
/// <returns></returns>
CollisionInfo TestCollisionWithLineSegment(float rotateBy, Vector2 lineStart, Vector2 lineEnd)
{
CollisionInfo ret = new CollisionInfo();
ret.Fraction = 1;
for (int i = 0; i < _points.Length; i++)
{
Vector2 p = _points[i];
float length = (p - _centerOfMass).Length();
LineIntersectCircleResult info = TestLineIntersectsCircle(lineStart, lineEnd, CenterOfMass, length);
//Game.ArrowCollection.AddArrow("test4" + i, Vector2.Zero, Vector2.Zero, Color.Orange);
if (info.Intersects)
{
//Game.ArrowCollection.AddArrow("test" + i, info.Intersect1, info.Intersect1, Color.Green);
//Game.ArrowCollection.AddArrow("test2" + i, info.Intersect2, info.Intersect2, Color.Green);
for (int a = 0; a < 2; a++)
{
float t;
Vector2 intersection;
if (a == 0)
{
t = info.T1;
intersection = info.Intersect1;
}
else
{
t = info.T2;
intersection = info.Intersect2;
}
if (t >= 0 && t < 1)
{
Vector2 v = ToWorld(p) - ToWorld(Vector2.Zero);
//Game.ArrowCollection.AddArrow("sadad", ToWorld(Vector2.Zero), ToWorld(p), Color.RoyalBlue);
//Game.ArrowCollection.AddArrow("sadad2", ToWorld(Vector2.Zero), intersection, Color.GreenYellow);
float angleToIntersect = Util.AngleBetween(CenterOfMass, intersection);
float angleToPoint = Util.AngleBetween(CenterOfMass, ToWorld(p));
float angleBeforeHit = Util.AngleBetween(angleToPoint, angleToIntersect);
float fractionIntersect = angleBeforeHit / rotateBy;
if (fractionIntersect > 0f && fractionIntersect < 1f && fractionIntersect < ret.Fraction)
{
ret.IsCollision = true;
ret.Fraction = fractionIntersect;
ret.IndexOfStriking = i;
ret.Impact = intersection;
ret.Type = CollisionType.VertexStrikesEdge;
}
}
}
}
}
return(ret);
}
