如何像Canvas globalCompositeOperation那样模拟较轻的效果？

Question

每年年底，我都会制作一个烟花展示画布效果(Javascript)，最后一个是：

http://js1k.com/2011-dysentery/demo/955

这个效果很简单:许多用createRadialGradient()方法填充的圆圈，具有一定的透明度。秘诀在于它的属性：

globalCompositeOperation = "lighter";

使用时，所有的颜色都混合在一起，给人一种光感。今年，我想用SFML/C++做同样的事情。我是SFML的乞讨者，不知道从哪里开始做这个效果。谁能告诉我如何在SFML中模拟画布globalCompositeOperation()？

Answer 1

您可以使用sf::Blend::Mode获得此效果。请参阅此示例：

    #include <SFML/Graphics.hpp>

    int main()
    {
        sf::RenderWindow window(sf::VideoMode(400, 400), "Blend::Mode Sample");
        sf::Shape square = sf::Shape::Rectangle(100, 100, 200, 200, sf::Color(250, 30, 30));
        sf::Shape circle1 = sf::Shape::Circle(100, 100, 50, sf::Color(30, 30, 250));
        sf::Shape circle2 = sf::Shape::Circle(300, 100, 50, sf::Color(30, 30, 250));
        sf::Shape circle3 = sf::Shape::Circle(100, 300, 50, sf::Color(30, 30, 250));
        sf::Shape circle4 = sf::Shape::Circle(300, 300, 50, sf::Color(30, 30, 250));
        circle1.SetBlendMode(sf::Blend::Alpha);
        circle2.SetBlendMode(sf::Blend::Add);
        circle3.SetBlendMode(sf::Blend::Multiply);
        circle4.SetBlendMode(sf::Blend::None);
        while (window.IsOpened())
        {
            sf::Event event;
            while (window.PollEvent(event))
                if (event.Type == sf::Event::Closed)
                    window.Close();

            window.Clear();
            window.Draw(square);
            window.Draw(circle1);
            window.Draw(circle2);
            window.Draw(circle3);
            window.Draw(circle4);
            window.Display();
        }
    }

输出：

​

​

我认为你想要的效果应该是SetBlendMode(sf::Blend::Add)。