Is it possible to create a line with circles?

[Xrey274]

So i am trying to draw a consistent free line with circles along(sf::CircleShape). It works if I move the mouse slowly, but the circles get big gaps if i move it quickly. I was wondering if it possible to resolve this?

#include <SFML/Graphics.hpp>
#include <iostream>

int main()
{
    sf::RenderWindow window(sf::VideoMode(1920, 1080), "Test");

    sf::Event event;

    std::vector<sf::CircleShape> circles;

    sf::Vector2f mouseCoords = window.mapPixelToCoords(sf::Vector2i(sf::Mouse::getPosition(window)));

    while(window.isOpen())
    {
        mouseCoords = window.mapPixelToCoords(sf::Vector2i(sf::Mouse::getPosition(window)));

        while(window.pollEvent(event))
        {
            if(event.type == sf::Event::Closed)
            {
                window.close();
            }

            if(event.type == sf::Event::MouseMoved)
            {
                sf::CircleShape newCircle;

                newCircle.setPosition(mouseCoords);
                newCircle.setRadius(3);
                newCircle.setFillColor(sf::Color::Black);

                circles.push_back(newCircle);
            }
        }
        window.clear(sf::Color::White);

        for(auto i : circles)
        {
            window.draw(i);
        }

        window.display();
    }
}
 

[Laurent]

Instead of just adding one circle where the mouse is, add as many circles as needed (constant spacing) between the previous mouse position and the current one.

[eXpl0it3r]

You'd have to interpolate the position in-between.
The simplest approach would be to connect each point with a line.
If you want rounded ends, you could use something like the Roun Ended Lines: https://github.com/SFML/SFML/wiki/Source:-Round-Ended-Lines
If you just want a line with variable thickness, you could get the Selba Ward Line: https://github.com/Hapaxia/SelbaWard/wiki/Line
Or if you want smoother interpolation, you could try to construct a spline path with Selba Ward's Spline: https://github.com/Hapaxia/SelbaWard/wiki/Spline

[Xrey274]

Just exactly why do I need to interpolate? Why can't the program keep up with the mouse?

[eXpl0it3r]

Because you're not running your program at infinite small frame time. So for 60 fps, you can move the mouse quite far within 16ms.