Lights with blending, doing something wrong.

[Moonkis]

I'm trying to implement some basic light using blending. It's based of this https://dl.dropboxusercontent.com/u/36451301/ld/ld27/index.html


I'm trying to implement it by doing it in a few small steps:

You must do it this way:
- fill a render-texture (which covers the whole window) with the dark color
- draw your light(s) to the render-texture with sf::BlendAdd
- draw the render-texture on top of your scene with sf::BlendMultiply

but for some reason the only thing I get is an completely black screen, I'm not sure what exactly I'm doing wrong. If I use Multiply when drawing the lightmap-buffer it litterly only shows black.

Here is a minimal code example:

int main()
{
        sf::Sprite s_lightmap;
        sf::Sprite s_light;

        sf::RenderTexture t_lightmap;
        sf::Texture t_light;

        t_lightmap.create(800,600);
        t_light.loadFromFile("light.png");

        sf::Color ambient(0,0,0,255);
        sf::Color lightColor(255,0,0,178);

        s_light.setTexture(t_light);
        s_light.setColor(lightColor);

        sf::RenderWindow window(sf::VideoMode(800,600,32),"Window");
        sf::Event event;

        while(window.isOpen())
        {
                while(window.pollEvent(event))
                {

                }
                window.clear(sf::Color::Blue);
                t_lightmap.clear(ambient);
                t_lightmap.draw(s_light, sf::BlendMode::BlendAdd);
                s_lightmap.setTexture(t_lightmap.getTexture());
                window.draw(s_lightmap, sf::BlendMode::BlendMultiply);
               
                window.display();
        }

        return 0;
}
 

[FRex]

Try calling display on render texture before drawing it to window.

[Laurent]

Your light is pure red. The lit environment is pure blue. Even in real life the result would be black