Factorio Rail bounding box logic

Rail.cpp

std::pair<BoundingBox, BoundingBox> Rail::calculateBoundingBoxes(MapPosition position,
                                                                 Direction direction,
                                                                 RailBendingType bendingType,
                                                                 const BoundingBox& collisionBoundingBox,
                                                                 const BoundingBox* secondaryCollisionBoundingBox)
{
  std::pair<BoundingBox, BoundingBox> boundingBoxes;

  if (bendingType == RailBendingType::Straight)
  {
    if (direction.isDiagonal())
    {
      boundingBoxes.first = BoundingBox(BoundingBox(-0.65, -0.7, 0.65, 0.7), position);
      Vector movingVector(Math::sqrt_2 / 2, direction);
      boundingBoxes.first.orientation = direction.left90();
      boundingBoxes.first += movingVector;
    }
    else
    {
      boundingBoxes.first = BoundingBox(collisionBoundingBox, position);
      if (direction == Direction::East)
        boundingBoxes.first.orientation = direction;
      else
        assert(direction == Direction::North /* Non-diagonal rail directions should be always "normalized" to North or East.*/);
    }
  }
  else
  {
    Direction primaryDirection = Rail::primaryTurnRailDirection(direction);
    boundingBoxes.first = BoundingBox(BoundingBox(collisionBoundingBox, primaryDirection), position);
    boundingBoxes.second = BoundingBox(*secondaryCollisionBoundingBox, position);
    boundingBoxes.second.orientation += RealOrientation(primaryDirection);
    Direction trueDirection = direction;
    if (!trueDirection.isDiagonal())
      --trueDirection;
    Vector movingVector(Math::sqrt_2, trueDirection.opposite());
    boundingBoxes.first += movingVector;
    boundingBoxes.first -= Vector(1.29, primaryDirection);

    boundingBoxes.second += movingVector;
    boundingBoxes.second -= Vector(1.3, primaryDirection);
    RealOrientation secondaryOrientation(direction);
    if (direction.isDiagonal())
      boundingBoxes.second.orientation += 0.09;
    else
    {
      boundingBoxes.second.orientation -= 0.09;
      secondaryOrientation -= 0.125;
    }
    boundingBoxes.second += Vector(1.5, primaryDirection);
    boundingBoxes.second += Vector(1.85, secondaryOrientation);
  }

  return boundingBoxes;
}

Direction Rail::primaryTurnRailDirection(Direction orientation)
{
  if (!orientation.isDiagonal())
    return orientation;
  return orientation.left45();
}