delegate property

Implementation

@override
Shape get delegate {
  if (rings < 1) throw ArgumentError('rings must be >= 1, got $rings.');

  final halfHeight = height * 0.5;
  final profile = <Vector2>[];
  final normals = <Vector2>[];

  void addHemisphereRow(double phi, double centreY) {
    final cosPhi = math.cos(phi);
    final sinPhi = math.sin(phi);
    profile.add(Vector2(radius * cosPhi, centreY + radius * sinPhi));
    // Normals are radial about the corresponding hemisphere centre, which is
    // also correct along the cylindrical middle where phi is 0.
    normals.add(Vector2(cosPhi, sinPhi));
  }

  for (var k = 0; k <= rings; k++) {
    addHemisphereRow(
      -math.pi / 2.0 + (math.pi / 2.0) * (k / rings),
      -halfHeight,
    );
  }
  for (var k = 0; k <= rings; k++) {
    addHemisphereRow((math.pi / 2.0) * (k / rings), halfHeight);
  }

  return LatheShape(
    profile: profile,
    profileNormals: normals,
    segments: segments,
    name: name,
  );
}