Origin Scaling

[Jalfor]

I'm unsure as to whether this was intentional or not, but when scaling anything in SFML 2, it also scales the origin. This for example -

#include <SFML/Graphics.hpp>

int main()
{
    sf::RenderWindow window(sf::VideoMode(800, 600), "Origin Scaling");
    sf::RectangleShape rectangle;
    rectangle.setSize(sf::Vector2f(100, 50));
    rectangle.setScale(0.25, 0.25);
    rectangle.setOrigin(-300, -300);

    while (1)
    {
        window.draw(rectangle);
        window.display();
    }
}
 

will not move the rectangle 300 pixels away from the left and 300 from the top, but rather a quarter of that.

[Laurent]

If the rectangle is initially 300 pixels away from the transformation origin, and you apply a scaling of 0.25, its final position is 300 * 0.25 away from the origin. That's what scaling does, what else did you expect?

[Jalfor]

I just didn't expect it to affect the origin. Anyway, I fixed it now by dividing origin by the scale when getting the origin and multiplying it by the scale when setting it.

[Laurent]

It doesn't affect the origin. The origin hasn't moved after scaling, it's the top-left corner of the rectangle which has moved closer to the origin.

The scale formula is simple: final_point = source_point * scale. If the top-left corner is at (300, 300), after scaling it ends up at (300 * 0.25, 300 * 0.25) from the origin.

Anyway, I fixed it now by dividing origin by the scale when getting the origin and multiplying it by the scale when setting it.

So your own "origin" is at a fixed distance from the top-left corner, and moves in the absolute coordinate system when you scale your entity. This is a strange way to handle it. Why do you need that? Can't you just leave the origin to the top-left corner, and use the position to offset the rectangle?