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General / Trying to implement DeWITTER's game loop.

« on: January 22, 2013, 02:22:14 pm »

Hello. I'm trying to get the game loop from http://www.koonsolo.com/news/dewitters-gameloop/ to work on my project. The code works fine, however the interpolated object will stutter slightly while the non-interpolated object runs very smooth. I can't seem to figure out why and I was wondering if anyone could help me out with this.

Here's my code:

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

const int TICKS_PER_SECOND = 25;
const int SKIP_TICKS = 1000 / TICKS_PER_SECOND;
const int MAX_FRAMESKIP = 5;

//StateManager TargetState;

int main()
{
    sf::RenderWindow Window(sf::VideoMode(800,600,32), "Test", !sf::Style::Resize | sf::Style::Close);

    // Game loop variables
    sf::Clock ticker;
    sf::Int32 next_game_tick = ticker.getElapsedTime().asMilliseconds();
    int loops;
    float interpolation;

    //TargetState.changeState(MenuState::Instance(&Window));

    while(Window.isOpen()) {
        //TargetState.input();

        // Update the game
        loops = 0;
        while(ticker.getElapsedTime().asMilliseconds() > next_game_tick && loops < MAX_FRAMESKIP) {
            //TargetState.update();
            next_game_tick += SKIP_TICKS;
            loops++;
        }

        interpolation = float(ticker.getElapsedTime().asMilliseconds() + SKIP_TICKS - next_game_tick)
                        / float (SKIP_TICKS);

        Window.clear();

        //TargetState.draw(interpolation);

        sf::Font font;
        font.loadFromFile("arial.ttf");
        sf::Text test("###", font, 250);
        sf::Text test2("###", font, 250);

        static float lex = 0.0;

        test.setPosition(lex + interpolation, 0);
        test2.setPosition(lex , 200);
        lex += 0.05;

        Window.draw(test);
        Window.draw(test2);

        Window.display();
    }
    return 0;
}
 

As you can probably see the top "###" stutters a bit while the bottom "###" runs very smoothly.