2D lighting with SFML

[demetri247]

I'm in the process of implementing a lighting engine, and I've been struggling with the polygon drawing. Currently, I'm using TriangleFan to connect the points that my raycasting algorithm has come in contact with, but I wish to achieve the opposite effect where everything except where the triangle fan is drawn is black and the play would have a limited view of their surroundings.

Is there a shape that could easily accomplish this?

[Hapax]

You could render that triangle fan (as white) to a render texture (the same size as the window) and then draw that render texture to the window with a multiplicative blend mode, leaving everything as-is where it is white and turning to black anything that is black.

[demetri247]

So something like this?

(click to show/hide)

        sf::RenderTexture texture;
        texture.create(1500, 1500);
        sf::BlendMode multiplicativeBlending = sf::BlendMultiply;
        texture.draw(TriangleFan);
        texture.display();
   
        m_game->window().clear();

        sf::Sprite sprite(texture.getTexture());
        m_game->window().draw(sprite, multiplicativeBlending);

The screen is just rendered as black, without the blending the Triangle fan is white and the rest is black but I can't see the textures underneath.

[demetri247]

nvm i was being silly and cleared the window  , works like a dream. Thank you!

[Hapax]

Yes, you need to clear, draw and display both the render texture and the window.

You are welcome! Pleased to help