raycast method

@override bool raycast(RayCastOutput output, RayCastInput input, Transform transform, int childIndex,)

Cast a ray against a child shape.

output is the ray-cast results. input the ray-cast input parameters. transform to be applied to the shape. childIndex the child shape index Returns true if the child shape is hit.

Implementation

@override
bool raycast(
  RayCastOutput output,
  RayCastInput input,
  Transform transform,
  int childIndex,
) {
  final inputP1 = input.p1;
  final inputP2 = input.p2;
  final tq = transform.q;
  final tp = transform.p;

  final positionX = tq.cos * position.x - tq.sin * position.y + tp.x;
  final positionY = tq.sin * position.x + tq.cos * position.y + tp.y;

  final sx = inputP1.x - positionX;
  final sy = inputP1.y - positionY;
  final b = sx * sx + sy * sy - radius * radius;

  // Solve quadratic equation.
  final rx = inputP2.x - inputP1.x;
  final ry = inputP2.y - inputP1.y;
  final c = sx * rx + sy * ry;
  final rr = rx * rx + ry * ry;
  final sigma = c * c - rr * b;

  // Check for negative discriminant and short segment.
  if (sigma < 0.0 || rr < settings.epsilon) {
    return false;
  }

  // Find the point of intersection of the line with the circle.
  var a = -(c + sqrt(sigma));

  // Is the intersection point on the segment?
  if (0.0 <= a && a <= input.maxFraction * rr) {
    a /= rr;
    output.fraction = a;
    output.normal.x = rx * a + sx;
    output.normal.y = ry * a + sy;
    output.normal.normalize();
    return true;
  }

  return false;
}