collidePolygonAndCircle method

void collidePolygonAndCircle(Manifold manifold, PolygonShape polygon, Transform xfA, CircleShape circle, Transform xfB,)

Compute the collision manifold between a polygon and a circle.

Implementation

void collidePolygonAndCircle(
  Manifold manifold,
  PolygonShape polygon,
  Transform xfA,
  CircleShape circle,
  Transform xfB,
) {
  manifold.pointCount = 0;
  // Vec2 v = circle.p;

  // Compute circle position in the frame of the polygon.
  // before inline:
  // Transform.mulToOutUnsafe(xfB, circle.p, c);
  // Transform.mulTransToOut(xfA, c, cLocal);
  // final double cLocalx = cLocal.x;
  // final double cLocaly = cLocal.y;

  // after inline:
  final circlep = circle.position;
  final xfBq = xfB.q;
  final xfAq = xfA.q;
  final cx = (xfBq.cos * circlep.x - xfBq.sin * circlep.y) + xfB.p.x;
  final cy = (xfBq.sin * circlep.x + xfBq.cos * circlep.y) + xfB.p.y;
  final px = cx - xfA.p.x;
  final py = cy - xfA.p.y;
  final cLocalX = xfAq.cos * px + xfAq.sin * py;
  final cLocalY = -xfAq.sin * px + xfAq.cos * py;
  // end inline

  // Find the min separating edge.
  var normalIndex = 0;
  var separation = -double.maxFinite;
  final radius = polygon.radius + circle.radius;
  double s;
  final vertices = polygon.vertices;
  final normals = polygon.normals;

  for (var i = 0; i < vertices.length; i++) {
    // before inline
    // temp.set(cLocal).subLocal(vertices[i]);
    // double s = Vec2.dot(normals[i], temp);
    // after inline
    final vertex = vertices[i];
    final tempX = cLocalX - vertex.x;
    final tempY = cLocalY - vertex.y;
    s = normals[i].x * tempX + normals[i].y * tempY;

    if (s > radius) {
      // early out
      return;
    }

    if (s > separation) {
      separation = s;
      normalIndex = i;
    }
  }

  // Vertices that subtend the incident face.
  final vertIndex1 = normalIndex;
  final vertIndex2 = vertIndex1 + 1 < vertices.length ? vertIndex1 + 1 : 0;
  final v1 = vertices[vertIndex1];
  final v2 = vertices[vertIndex2];

  // If the center is inside the polygon ...
  if (separation < settings.epsilon) {
    manifold.pointCount = 1;
    manifold.type = ManifoldType.faceA;

    final normal = normals[normalIndex];
    manifold.localNormal.x = normal.x;
    manifold.localNormal.y = normal.y;
    manifold.localPoint.x = (v1.x + v2.x) * .5;
    manifold.localPoint.y = (v1.y + v2.y) * .5;
    final mpoint = manifold.points[0];
    mpoint.localPoint.x = circlep.x;
    mpoint.localPoint.y = circlep.y;
    mpoint.id.zero();
    // end inline

    return;
  }

  // Compute barycentric coordinates
  final tempX = cLocalX - v1.x;
  final tempY = cLocalY - v1.y;
  final temp2X = v2.x - v1.x;
  final temp2Y = v2.y - v1.y;
  final u1 = tempX * temp2X + tempY * temp2Y;

  final temp3X = cLocalX - v2.x;
  final temp3Y = cLocalY - v2.y;
  final temp4X = v1.x - v2.x;
  final temp4Y = v1.y - v2.y;
  final u2 = temp3X * temp4X + temp3Y * temp4Y;

  if (u1 <= 0.0) {
    final dx = cLocalX - v1.x;
    final dy = cLocalY - v1.y;
    if (dx * dx + dy * dy > radius * radius) {
      return;
    }

    manifold.pointCount = 1;
    manifold.type = ManifoldType.faceA;
    manifold.localNormal.x = cLocalX - v1.x;
    manifold.localNormal.y = cLocalY - v1.y;
    manifold.localNormal.normalize();
    manifold.localPoint.setFrom(v1);
    manifold.points[0].localPoint.setFrom(circlep);
    manifold.points[0].id.zero();
  } else if (u2 <= 0.0) {
    final dx = cLocalX - v2.x;
    final dy = cLocalY - v2.y;
    if (dx * dx + dy * dy > radius * radius) {
      return;
    }

    manifold.pointCount = 1;
    manifold.type = ManifoldType.faceA;
    manifold.localNormal.x = cLocalX - v2.x;
    manifold.localNormal.y = cLocalY - v2.y;
    manifold.localNormal.normalize();
    manifold.localPoint.setFrom(v2);
    manifold.points[0].localPoint.setFrom(circlep);
    manifold.points[0].id.zero();
  } else {
    final fcx = (v1.x + v2.x) * .5;
    final fcy = (v1.y + v2.y) * .5;

    final tx = cLocalX - fcx;
    final ty = cLocalY - fcy;
    final normal = normals[vertIndex1];
    separation = tx * normal.x + ty * normal.y;
    if (separation > radius) {
      return;
    }

    manifold.pointCount = 1;
    manifold.type = ManifoldType.faceA;
    manifold.localNormal.setFrom(normals[vertIndex1]);
    manifold.localPoint.x = fcx; // (faceCenter)
    manifold.localPoint.y = fcy;
    manifold.points[0].localPoint.setFrom(circlep);
    manifold.points[0].id.zero();
  }
}