A SFML application that draws a cardioid.

cardioid_sfml.cpp

#include <SFML/Graphics.hpp>
#include <algorithm>
#include <cmath>

class Cardioid
{
public:
    Cardioid()
        : m_radius(400), m_num_lines(150), m_counter(0.0f), m_inc(0.01f), m_translate(sf::Vector2i(1000/2, 600/2)){}
    void draw(sf::RenderWindow& w)
    {
        int time = m_clock.getElapsedTime().asMilliseconds();
        m_radius = 250 + 50 * std::abs(std::sin(time * 0.004) - 0.5);
        float factor = 1 + 0.0001 * time;
        sf::Color color = getColor();
        for(int i = 0; i < m_num_lines; ++i)
        {
            float theta = ( (2 * M_PI) / m_num_lines) * i;
            int x1 = m_radius * std::cos(theta) + m_translate.x;
            int y1 = m_radius * std::sin(theta) + m_translate.y;

            int x2 = m_radius * std::cos(factor*theta) + m_translate.x;
            int y2 = m_radius * std::sin(factor*theta) + m_translate.y;

            sf::Vertex line[] =
            {
                sf::Vertex(sf::Vector2f(x1, y1), color),
                sf::Vertex(sf::Vector2f(x2, y2), color)
            };
            w.draw(line, 2, sf::Lines);
        }
    }
    sf::Color getColor(){
        m_counter += m_inc;
        if (!(0.009 < m_counter && m_counter < 1)) {
            m_counter = std::max(std::min(m_counter, 1.0f), 0.0f);
            m_inc = -m_inc;
        }
        sf::Color color1 = sf::Color::Red;
        sf::Color color2 = sf::Color::Green;
        int r = (color2.r - color1.r) * m_counter + color1.r;
        int g = (color2.g - color1.g) * m_counter + color1.g;
        int b = (color2.b - color1.b) * m_counter + color1.b;
        return sf::Color(r, g, b);
    }

private:
    int   m_radius;
    int   m_num_lines;
    float m_counter;
    float m_inc;
    sf::Clock m_clock;
    sf::Vector2i m_translate;
};

int main()
{
    const unsigned int FPS = 60; //The desired FPS. (The number of updates each second).
    sf::RenderWindow window(sf::VideoMode(1000, 600), "Cardioid SFML C++");
    window.setFramerateLimit(FPS);
    Cardioid cardioid;
    sf::Event ev;
    while (window.isOpen())
    {
        //Handle events
        while (window.pollEvent(ev))
        {
            if (ev.type == sf::Event::Closed)
                window.close();
        }
        // Draw stuff
        window.clear();
        cardioid.draw(window);
        window.display();
    }
}