/// <summary>
/// Computes an intersection of the segment and the circle
/// </summary>
public static bool SegmentCircle(Vector2 segmentA, Vector2 segmentB, Vector2 circleCenter, float circleRadius,
out IntersectionSegmentCircle intersection)
{
Vector2 segmentAToCenter = circleCenter - segmentA;
Vector2 fromAtoB = segmentB - segmentA;
float segmentLength = fromAtoB.magnitude;
if (segmentLength < Geometry.Epsilon)
{
float distanceToPoint = segmentAToCenter.magnitude;
if (distanceToPoint < circleRadius + Geometry.Epsilon)
{
if (distanceToPoint > circleRadius - Geometry.Epsilon)
{
intersection = IntersectionSegmentCircle.Point(segmentA);
return(true);
}
intersection = IntersectionSegmentCircle.None();
return(true);
}
intersection = IntersectionSegmentCircle.None();
return(false);
}
Vector2 segmentDirection = fromAtoB.normalized;
float centerProjection = Vector2.Dot(segmentDirection, segmentAToCenter);
if (centerProjection + circleRadius < -Geometry.Epsilon ||
centerProjection - circleRadius > segmentLength + Geometry.Epsilon)
{
intersection = IntersectionSegmentCircle.None();
return(false);
}
float sqrDistanceToLine = segmentAToCenter.sqrMagnitude - centerProjection * centerProjection;
float sqrDistanceToIntersection = circleRadius * circleRadius - sqrDistanceToLine;
if (sqrDistanceToIntersection < -Geometry.Epsilon)
{
intersection = IntersectionSegmentCircle.None();
return(false);
}
if (sqrDistanceToIntersection < Geometry.Epsilon)
{
if (centerProjection < -Geometry.Epsilon ||
centerProjection > segmentLength + Geometry.Epsilon)
{
intersection = IntersectionSegmentCircle.None();
return(false);
}
intersection = IntersectionSegmentCircle.Point(segmentA + segmentDirection * centerProjection);
return(true);
}
// Line intersection
float distanceToIntersection = Mathf.Sqrt(sqrDistanceToIntersection);
float distanceA = centerProjection - distanceToIntersection;
float distanceB = centerProjection + distanceToIntersection;
bool pointAIsAfterSegmentA = distanceA > -Geometry.Epsilon;
bool pointBIsBeforeSegmentB = distanceB < segmentLength + Geometry.Epsilon;
if (pointAIsAfterSegmentA && pointBIsBeforeSegmentB)
{
Vector2 pointA = segmentA + segmentDirection * distanceA;
Vector2 pointB = segmentA + segmentDirection * distanceB;
intersection = IntersectionSegmentCircle.TwoPoints(pointA, pointB);
return(true);
}
if (!pointAIsAfterSegmentA && !pointBIsBeforeSegmentB)
{
// The segment is inside, but no intersection
intersection = IntersectionSegmentCircle.None();
return(true);
}
bool pointAIsBeforeSegmentB = distanceA < segmentLength + Geometry.Epsilon;
if (pointAIsAfterSegmentA && pointAIsBeforeSegmentB)
{
// Point A intersection
intersection = IntersectionSegmentCircle.Point(segmentA + segmentDirection * distanceA);
return(true);
}
bool pointBIsAfterSegmentA = distanceB > -Geometry.Epsilon;
if (pointBIsAfterSegmentA && pointBIsBeforeSegmentB)
{
// Point B intersection
intersection = IntersectionSegmentCircle.Point(segmentA + segmentDirection * distanceB);
return(true);
}
intersection = IntersectionSegmentCircle.None();
return(false);
}
/// <summary>
/// Computes an intersection of the segment and the circle
/// </summary>
public static bool SegmentCircle(Segment2 segment, Circle2 circle, out IntersectionSegmentCircle intersection)
{
return(SegmentCircle(segment.a, segment.b, circle.center, circle.radius, out intersection));
}
