How to do shaders on the frame buffer correctly?

[Rob92]

I want to apply a fragment shader to the screen, so I can manipulate the frame buffer.

At the moment I am doing it like this:

if (m_frameBufferStates.shader != nullptr)
{
        m_frameBufferTexture.update(*m_window);
        m_frameBufferSprite.setTexture(m_frameBufferTexture);
        m_window->draw(m_frameBufferSprite, m_frameBufferStates);
}

I noticed that this cost me a substantial chunk of performance. (because of sf::Texture update function)
I still have more than enough FPS but I was wondering if there is a better way to do this?

[victorlevasseur]

sf::RenderTexture ?

[Rob92]

Hi, I tried that but I couldnt figure out how to copy the screen buffer to the rendertarget. The draw function askes for a Drawable&.

[Hapax]

sf::RenderTexture renderTexture;
// ...
{
    renderTexture.clear();
    renderTexture.draw(allGameObjects);
    renderTexture.display();
    window.clear()
    window.draw(sf::Sprite(renderTexture.getTexture()), states);
    window.display();
}

[victorlevasseur]

To add some precision to Hapax message : obviously, you need to draw your whole game to the sf::RenderTexture instead of the window. And do not forget to call clear() and display() on the sf::RenderTexture itself too.

[Hapax]

To add some precision to Hapax message : obviously, you need to draw your whole game to the sf::RenderTexture instead of the window. And do not forget to call clear() and display() on the sf::RenderTexture itself too.

I've modified my above post to be more clear and to include the advice you mentioned

[Rob92]

Thank you both, it works and gives me a bit better performance