Messages

1

General / Re: Generic Game Loop

« on: December 19, 2012, 03:12:45 am »

Oops I just realized leaving that conditional in there causes the ball to move slower than it should. I took it out and now it acts normally. I guess I sort of answered my own question.

2

General / Re: Generic Game Loop

« on: December 19, 2012, 03:02:27 am »

I've heard about the issues using sleep before. By saying I won't get a "fully fixed" frame rate do you mean it simply won't be 100% accurate? With setFramerateLimit(60) I get ~62 fps. That's fine with me if it's slightly off.

If I understand correctly I can modify it like so:

#include <SFML\Graphics.hpp>
using namespace sf;

int main()
{
    const float FPS = 60.0f; //The desired FPS. (The number of updates each second).
    bool redraw = true;      //Do I redraw everything on the screen?

    RenderWindow window(VideoMode(300, 300, 32), "Hello");
    window.setFramerateLimit(FPS);
    Clock clock;
    CircleShape circle(10.0f);
    circle.setOrigin(10.0f, 10.0f);
    circle.setPosition(0, 150.0f);

    Event ev;
    while (window.isOpen())
    {
        //Wait until 1/60th of a second has passed, then update everything.
        if (clock.getElapsedTime().asSeconds() >= 1.0f / FPS)
        {
            redraw = true; //We're ready to redraw everything
            circle.move(1.0f, 0);
            clock.restart();
        }

        //Handle input
        while (window.pollEvent(ev))
        {
            if (ev.type == Event::Closed) window.close();
        }

        //Draw stuff if ready
        if (redraw)
        {
            redraw = false;
            window.clear(Color(0, 0, 0));
            window.draw(circle);
            window.display();
        }
    }

    return 0;
}
 

Can I remove the

if (clock.getElapsedTime().asSeconds() >= 1.0f / FPS)

condition and the clock entirely, or will that cause the circle's speed to be FPS-dependent? I'm trying to understand exactly how much setFramerateLimit() does for me automatically.

Thank you for your time. 

3

General / Generic Game Loop

« on: December 18, 2012, 10:52:31 pm »

Hello. I'm relatively new to SFML, but I've dabbled around with Allegro and game engines for awhile. I'm trying to create a basic fixed time-step loop for a game in SFML. I based the loop off a tutorial for Allegro. You can see the tutorial here: http://fixbyproximity.com/2011/08/2d-game-dev-part-4-1-timing-our-game-loop-2/ . The sourcecode is below the video if you're interested.

Anyways, I want the game to act independent of FPS. I wrote a simple program below. I want the circle to take 5 seconds to go from the left side to the right side of the screen (It moves 1 pixel every 1/60th of a second).

#include <SFML\Graphics.hpp>
using namespace sf;

int main()
{
        const float FPS = 60.0f; //The desired FPS. (The number of updates each second).
        bool redraw = true;      //Do I redraw everything on the screen?

        RenderWindow window(VideoMode(300, 300, 32), "Hello");
        Clock clock;
        CircleShape circle(10.0f);
        circle.setOrigin(10.0f, 10.0f);
        circle.setPosition(0, 150.0f);

        Event ev;
        while (window.isOpen())
        {
                //Wait until 1/60th of a second has passed, then update everything.
                if (clock.getElapsedTime().asSeconds() >= 1.0f / FPS)
                {
                        redraw = true; //We're ready to redraw everything
                        circle.move(1.0f, 0);
                        clock.restart();
                }
                else //Sleep until next 1/60th of a second comes around
                {
                        Time sleepTime = seconds((1.0f / FPS) - clock.getElapsedTime().asSeconds());
                        sleep(sleepTime);
                }

                //Handle input
                while (window.pollEvent(ev))
                {
                        if (ev.type == Event::Closed) window.close();
                }

                //Draw stuff if ready
                if (redraw)
                {
                        redraw = false;
                        window.clear(Color(0, 0, 0));
                        window.draw(circle);
                        window.display();
                }
        }

        return 0;
}

Fraps reports 58-59 fps, and the circle takes 5 seconds to do its thing. If I remove the if(redraw) condition, Fraps reports around 110 fps, and the circle still takes 5 seconds (which is what I want).

My questions is: is the above code a good way to approach this? I'm just worried that I'll discover some flaw halfway into a game and have to change everything.