Resolution-Independent Rendering?

[pixartist]

Hi,
I'm new to smfl and I was wondering how I can scale my content to fit into the window without having a global scale variable which has to be used in every frame. I tried a simple approach with RenderTextures, but calling the GetTexture() method every frame seems to be VERY slow. Any ideas?

[Rhimlock]

Did you try Views?

[pixartist]

No, but i found a tutorial doing EXACTLY what I'm doing, which is weird, since this method reduces the performance of my program to about 5 frames per second:

window.clear();
                renderTarget.clear();
        RenderFrame();
                renderTarget.display();
                contentTexture = renderTarget.getTexture();
                auto spr = sf::Sprite(contentTexture);
                window.draw(spr);
        window.display();

edit: I will use views now, I'm still interested why this does kill the performance.

[FRex]

window.clear();
        renderTarget.clear();
        RenderFrame();
        renderTarget.display();
        //contentTexture = renderTarget.getTexture(); // NO-NO
        auto spr = sf::Sprite(renderTarget.getTexture());//Yes!
        window.draw(spr);//could be window.draw(sf::Sprite(renderTarget.getTexture()));
        window.display();

You're making a roundtrip to CPU and then back to GPU every frame now, which is terrible really and takes a long time.
https://github.com/SFML/SFML/blob/master/src/SFML/Graphics/Texture.cpp#L82

[pixartist]

There is no way to render to a texture on the GPU ?

[FRex]

Your question makes no sense, everything is rendered on GPU but what you are doing is copying texture every frame(instead of using the render texture's texture directly) which takes a long time because it goes from GPU to CPU then back to GPU, you should do that instead:

window.clear();
        renderTarget.clear();
        RenderFrame();
        renderTarget.display();
        auto spr = sf::Sprite(renderTarget.getTexture());
        window.draw(spr);
        window.display();

[pixartist]

I did that first, it makes absolutely no difference. GetTexture does not return a pointer, so the texture will be copied anyway, won't it?

[FRex]

It returns a const reference and Sprite takes a const reference so there is no copy then.

[pixartist]

okay thanks.

[eXpl0it3r]

The roudtrip via RenderTexture isn't really needed either (unless I didn't understand what you're trying to do), because as Ghosa pointed out, you can simply use an sf::View to make the content fit your window. The official tutorials explain views quite well, you should read it!

[pixartist]

Yeah but views can't be nested right ?

[pixartist]

Also how do I draw a sprite with a fixed size? My sprite is always rendered fullscreen? I looked into the tutorials, they all describe relative scaling, but none shows how to draw s sprite with an absolute size.

[eXpl0it3r]

Not sure what you mean with nested, but you can use multiple views.

There's no absolute scaling. A sprite simple represents a texture' axis aligned bounding box. If you want it absolute scaled you need to calculate the scaling yourself.