bool Circle::DoesIntersect(Vector2f p1, Vector2f p2) const
{
//Transform so that this circle is at the origin.
p1 -= Pos;
p2 -= Pos;
float determinant = (p1.x * p2.y) - (p2.x * p1.y);
float segmentLenSqr = p1.DistanceSquared(p2);
float discriminant = (Radius * Radius * segmentLenSqr) -
(determinant * determinant);
return discriminant >= -0.01f;
}
unsigned int Circle::GetIntersections(Vector2f p1, Vector2f p2, Vector2f outPs[2]) const
{
//Transform so that this circle is at the origin.
p1 -= Pos;
p2 -= Pos;
float determinant = (p1.x * p2.y) - (p2.x * p1.y);
float segmentLenSqr = p1.DistanceSquared(p2);
float discriminant = (Radius * Radius * segmentLenSqr) -
(determinant * determinant);
if (discriminant < -0.01f) return 0;
else
{
float distY = p2.y - p1.y,
distX = p2.x - p1.x;
float invSegmentLenSqr = 1.0f / segmentLenSqr;
float xPart1 = determinant * distY,
yPart1 = -determinant * distX;
if (discriminant > 0.0f)
{
float xPart2 = (distY < 0.0f ? -1.0f : 1.0f) * distX * sqrtf(discriminant),
yPart2 = fabsf(distY) * sqrtf(discriminant);
outPs[0] = Vector2f((xPart1 + xPart2) * invSegmentLenSqr,
(yPart1 + yPart2) * invSegmentLenSqr);
outPs[1] = Vector2f((xPart1 - xPart2) * invSegmentLenSqr,
(yPart1 - yPart2) * invSegmentLenSqr);
outPs[0] += Pos;
outPs[1] += Pos;
return 2;
}
else
{
outPs[0] = Vector2f(xPart1 * invSegmentLenSqr,
yPart1 * invSegmentLenSqr);
outPs[0] += Pos;
return 1;
}
}
}
