computeDistanceToOut method

@override double computeDistanceToOut(Transform xf, Vector2 p, int childIndex, Vector2 normalOut,)

Compute the distance from the current shape to the specified point. This only works for convex shapes.

xf is the shape world transform. p is a point in world coordinates. normalOut returns the direction in which the distance increases. Returns the distance from the current shape.

Implementation

@override
double computeDistanceToOut(
  Transform xf,
  Vector2 p,
  int childIndex,
  Vector2 normalOut,
) {
  final xfqc = xf.q.cos;
  final xfqs = xf.q.sin;
  final xfpx = xf.p.x;
  final xfpy = xf.p.y;
  final v1x = (xfqc * vertex1.x - xfqs * vertex1.y) + xfpx;
  final v1y = (xfqs * vertex1.x + xfqc * vertex1.y) + xfpy;
  final v2x = (xfqc * vertex2.x - xfqs * vertex2.y) + xfpx;
  final v2y = (xfqs * vertex2.x + xfqc * vertex2.y) + xfpy;

  var dx = p.x - v1x;
  var dy = p.y - v1y;
  final sx = v2x - v1x;
  final sy = v2y - v1y;
  final ds = dx * sx + dy * sy;
  if (ds > 0) {
    final s2 = sx * sx + sy * sy;
    if (ds > s2) {
      dx = p.x - v2x;
      dy = p.y - v2y;
    } else {
      dx -= ds / s2 * sx;
      dy -= ds / s2 * sy;
    }
  }

  final d1 = sqrt(dx * dx + dy * dy);
  if (d1 > 0) {
    normalOut.x = 1 / d1 * dx;
    normalOut.y = 1 / d1 * dy;
  } else {
    normalOut.x = 0.0;
    normalOut.y = 0.0;
  }
  return d1;
}