Unwanted outline appearing on RectangleShape

[lexected]

Hello!

I'm using this code

rectangle = new sf::RectangleShape(size);
rectangle->setFillColor(sf::Color::White);
rectangle->setOutlineThickness(0.f);
rectangle->setOutlineColor(sf::Color::Transparent);
rectangle->setPosition(position);
target.draw(*rectangle);
 

and yet I'm experiencing something like this


If you look closer you will see a thin gray border around the white boxes. However, it isn't present everyhere. For example, the third box has no border on the bottom side.

A similar thing happens to my textures applied on RectangleShape


No such thing is visible in Inkscape


Any idea what could be causing this?

[Hapax]

It might be an alpha problem.
If it's happening on textures with transparent sections, it's very likely.
The untextured shape, however, might cause edging if the edges/corners are not placed at exact co-ordinates. Are you using anti-aliasing?

For further investigation into your problem, please post a complete and minimal example.

[lexected]

Thank you for your answer.

What is "an alpha problem" and how can it be avoided?

To the untextured shape: I'm not using anti-aliasing. From what I understood from internet, there could be a rounding error of floats in the positions of vertices, but mine seem to be fine to me.

I also didn't mention that I'm rendering contents of a window (both texture and white box) into a RenderTexture, and only then I'm rendering that onto the background rectangle shape in the window.


I'd like to provide a minimal example, but when I tried to reproduce this problem with a new application, it wasn't there.

EDIT:
Ok, I did a bit of further "testing".
I found that those borders aren't there if I overlap two RectangleShapes of the same color.


I am now sure that the problem is in the RenderTexture step. Notice that the characters here are not blured, because I rendered the box directly into the RenderWindow.


EDIT2: SOLVED!
My RenderTexture´s IntRect was smaller (or different) than the size of the texture. That's it.

[lexected]

I'd still like to ask about that alpha problem. What is it? How could one avoid it? setSmooth, antialiasing or some other trick?

[Mario]

See my post in the other thread. Is there some specific reason you're trying to draw those rectangles as textures rather than primitives/polygons?