fromPoints static method

Circle? fromPoints(Vector2 p1, Vector2 p2, Vector2 p3)

Tries to create a Circle that intersects the 3 points, if it exists.

As long as the points are not co-linear, there is always exactly one circle intersecting all 3 points.

Implementation

static Circle? fromPoints(Vector2 p1, Vector2 p2, Vector2 p3) {
  final offset = p2.length2;
  final bc = (p1.length2 - offset) / 2.0;
  final cd = (offset - p3.length2) / 2.0;
  final det = (p1.x - p2.x) * (p2.y - p3.y) - (p2.x - p3.x) * (p1.y - p2.y);
  if (det == 0) {
    return null;
  }

  final centerX = (bc * (p2.y - p3.y) - cd * (p1.y - p2.y)) / det;
  final centerY = (cd * (p1.x - p2.x) - bc * (p2.x - p3.x)) / det;
  final radius = sqrt(pow(p2.x - centerX, 2) + pow(p2.y - centerY, 2));

  return Circle(Vector2(centerX, centerY), radius);
}