SFML community forums

Help => General => Topic started by: Sanction on August 11, 2015, 04:00:32 pm

Title: Weird movement in my program[SOLVED]
Post by: Sanction on August 11, 2015, 04:00:32 pm

I'm getting back into C++ before I forget it all.. I'm vary rusty. I'm following all the SFML books and tutorials.

The question I have is Why is my _Player movement is radical?
Is this because of the _Window.setFramerateLimit(FPS) ?

Main.cpp

(click to show/hide)

#include <iostream>
#include "Game.h"

using namespace std;

int main()
{
        Game game;
        game.run();
        return 0;
}
 

Game.cpp

(click to show/hide)

#include "Game.h"

Game::Game() : _Window(sf::VideoMode(640, 480), "Window"), _Player()
{
        _Window.setFramerateLimit(FPS);

        _Player.setRadius(20.f);
        _Player.setPosition(100.f, 100.f);
        _Player.setFillColor(sf::Color::Blue);

       
}

void Game::run()
{      
        //Game Loop
        while (_Window.isOpen())
        {
                //Handle Events
                processEvents();
                //Game Logic
                update();
                //Draw to Screen
                render();
        }
}

void Game::processEvents()
{
        sf::Event event;
        while (_Window.pollEvent(event))
        {       //Event Switch
                switch (event.type)
                {
                //Close Window
                case sf::Event::Closed:
                        _Window.close();
                        break;
                //Key Pressed
                case sf::Event::KeyPressed:
                        handlePlayerInput(event.key.code, true);
                        break;
                //Key Released
                case sf::Event::KeyReleased:
                        handlePlayerInput(event.key.code, false);
                        break;

                }
        }
}

void Game::update()
{
        sf::Vector2f movement(0.f, 0.f);
        if (_IsMovingUp)
                movement.y -= 1.f;
        if (_IsMovingDown)
                movement.y += 1.f;
        if (_IsMovingLeft)
                movement.x -= 1.f;
        if (_IsMovingRight)
                movement.x += 1.f;

        _Player.move(movement);
}

void Game::render()
{
        _Window.clear();
        _Window.draw(_Player);
        _Window.display();
}

void Game::handlePlayerInput(sf::Keyboard::Key key, bool isPressed)
{
        if (key == sf::Keyboard::W)
        {
                _IsMovingUp = isPressed;
                cout << "W: Pressed" << isPressed << endl;
        }
        if (key == sf::Keyboard::S)
        {
                _IsMovingDown = isPressed;
                cout << "S: Pressed" << isPressed << endl;
        }
        if (key == sf::Keyboard::A)
        {
                _IsMovingLeft = isPressed;
                cout << "A: Pressed" << isPressed << endl;
        }
        if (key == sf::Keyboard::D)
        {
                _IsMovingDown = isPressed;
                cout << "D: Pressed" << isPressed << endl;
        }
}
 

Game.h

(click to show/hide)

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

using namespace std;

class Game
{
public:

        Game();
        void run();

private:

        void processEvents();
        void update();
        void render();

        void handlePlayerInput(sf::Keyboard::Key key, bool isPressed);

private:

        const float FPS = 60.0f;

        sf::RenderWindow _Window;
        sf::CircleShape _Player;

        bool isPressed;

        bool _IsMovingUp;
        bool _IsMovingDown;
        bool _IsMovingLeft;
        bool _IsMovingRight;

};
 

Title: Re: Weird movement in my program
Post by: Jesper Juhl on August 11, 2015, 04:22:17 pm

Your update function always moves by a fixed amount. It doesn't take the time between frames into account.

I'd suggest reading these links:

http://gafferongames.com/game-physics/fix-your-timestep/
http://www.koonsolo.com/news/dewitters-gameloop/
http://gameprogrammingpatterns.com/game-loop.html
http://gameprogrammingpatterns.com/update-method.html

Title: Re: Weird movement in my program
Post by: Sanction on August 11, 2015, 04:29:17 pm

Thankyou.. I had a feeling something weird was going on I just could not put my finger on it.

Title: Re: Weird movement in my program
Post by: Sanction on August 11, 2015, 05:31:38 pm

So I read http://gameprogrammingpatterns.com/game-loop.html it was the most helpful to explaining what is going on..

I'm also trying to follow the book and compare something is not right here. same movement issues and the numbers don't seem right.

Game.cpp

(click to show/hide)

#include "Game.h"

Game::Game() : _Window(sf::VideoMode(640, 480), "Window"), _Player()
{
        //_Window.setFramerateLimit(FPS);

        _Player.setRadius(20.f);
        _Player.setPosition(100.f, 100.f);
        _Player.setFillColor(sf::Color::Blue);

       
}

void Game::run()
{      
        sf::Clock clock;
        sf::Time elapsedTime = sf::Time::Zero;
        while (_Window.isOpen())
        {
                //Handle Events
                processEvents();

                elapsedTime += clock.restart();
                cout << "> Before >" << elapsedTime.asSeconds() << endl;
                while (elapsedTime > TimesPerFrame)// sf::Time TimesPerFrame = sf::seconds(1.f / 60.f);
                {
                        elapsedTime -= TimesPerFrame;
                        cout << "< After <" << elapsedTime.asSeconds() << endl;
                        //Handle Events
                        processEvents();
                        //Game Logic
                        update();
                }

                //Draw to Screen
                render();
        }
}

void Game::processEvents()
{
        sf::Event event;
        while (_Window.pollEvent(event))
        {       //Event Switch
                switch (event.type)
                {
                //Close Window
                case sf::Event::Closed:
                        _Window.close();
                        break;
                //Key Pressed
                case sf::Event::KeyPressed:
                        handlePlayerInput(event.key.code, true);
                        break;
                //Key Released
                case sf::Event::KeyReleased:
                        handlePlayerInput(event.key.code, false);
                        break;

                }
        }
}

void Game::update()
{
        sf::Vector2f movement(0.f, 0.f);
        if (_IsMovingUp)
                movement.y -= 1.f;
        if (_IsMovingDown)
                movement.y += 1.f;
        if (_IsMovingLeft)
                movement.x -= 1.f;
        if (_IsMovingRight)
                movement.x += 1.f;

        _Player.move(movement);
}

void Game::render()
{
        _Window.clear();
        _Window.draw(_Player);
        _Window.display();
}

void Game::handlePlayerInput(sf::Keyboard::Key key, bool isPressed)
{
        if (key == sf::Keyboard::W)
        {
                _IsMovingUp = isPressed;
                cout << "W: Pressed" << isPressed << endl;
        }
        if (key == sf::Keyboard::S)
        {
                _IsMovingDown = isPressed;
                cout << "S: Pressed" << isPressed << endl;
        }
        if (key == sf::Keyboard::A)
        {
                _IsMovingLeft = isPressed;
                cout << "A: Pressed" << isPressed << endl;
        }
        if (key == sf::Keyboard::D)
        {
                _IsMovingDown = isPressed;
                cout << "D: Pressed" << isPressed << endl;
        }
}
 

Title: Re: Weird movement in my program
Post by: Jesper Juhl on August 11, 2015, 05:33:15 pm

I'd personally recommend the first link "Fix your timestep" as the best by far (try reading it again) :)

Title: Re: Weird movement in my program
Post by: Sanction on August 11, 2015, 06:18:36 pm

that just confusing me even more.

This should work, but I'm still running into the same problem..

void Game::run()
{      
        sf::Clock clock;
        sf::Time timeSinceLastUpdate = sf::Time::Zero;

        while (_Window.isOpen())
        {
                sf::Time elapsedTime = clock.restart();
                timeSinceLastUpdate += elapsedTime;
                while (timeSinceLastUpdate > TimesPerFrame)// sf::Time TimesPerFrame = sf::seconds(1.f / 60.f);
                {
                        timeSinceLastUpdate -= TimesPerFrame;

                        //Handle Events
                        processEvents();
                        //Game Logic
                        update();
                }

                //Draw to Screen
                render();
        }
}
 

Title: Re: Weird movement in my program
Post by: Sanction on August 11, 2015, 07:48:16 pm

I added in a function that shows my FramesPerSec and I'm getting like 340ish.. and it should be set at 60 :'( something isn't working correctly

Title: Re: Weird movement in my program
Post by: Hapax on August 11, 2015, 08:03:14 pm

TimesPerFrame is a confusing name for that particular variable since it's actually how much time each loop should process (aka timestep), not how many times it does so.
e.g. 1/60 would mean it would do something once every sixty seconds, not sixty times every one second. (when it's named "times per frame")

Quote from: Sanction on August 11, 2015, 07:48:16 pm

I added in a function that shows my FramesPerSec and I'm getting like 340ish.. and it should be set at 60 :'(

Your setFramerateLimit() is commented out.
If it's not, your calculations could be erred.

Quote from: Sanction on August 11, 2015, 06:18:36 pm

This should work

Although technically, I can't think right now of any logical reason other than overkill to avoid putting events in the inner (update) loop, I don't understand why you actually placed input and events inside that loop as even in the article you said helped you, they quite clearly don't do that:
(http://gameprogrammingpatterns.com/images/game-loop-fixed.png)

Title: Re: Weird movement in my program
Post by: Sanction on August 11, 2015, 08:44:50 pm

setFramerateLimit() was commented out because it would sleep my whole game loop and it was causing problems with eventpoll. That's how we got to creating fixed time step. (from my understanding and research is sleeps from the window.display() but don't take my word for it I've read so many forms about time step)

The reason the events were in the inner loop is because its straight out of the SFML book. What I have its identical to the source code. probably why I'm really confused on why this isn't working right. The book must be wrong.

Title: Re: Weird movement in my program
Post by: Arcade on August 11, 2015, 09:07:43 pm

Quote

setFramerateLimit() was commented out because it would sleep my whole game loop

I think Hapax pointed out that setFramerateLimit() is commented out because it could explain why your measured FPS is so high. You didn't show how you are measuring frame rate, but if you are just doing it from your main loop in Game::run(), then it would make sense for it to be high. There is nothing to slow it down. Your game logic (update) is running at roughly 60 FPS due to your fixed time step, but your game loop itself (with the render() call) is not being limited in any way.

Having said that, after reading this thread I'm not exactly sure what the problem is that we're trying to solve (probably because I don't have a way to test the code you posted right now). You said the player movement is radical, but I don't really know what that means. Is the player movement just not smooth looking or is it faster/slower than expected?

Title: Re: Weird movement in my program
Post by: Sanction on August 11, 2015, 09:22:07 pm

Its got to be something simple or something I'm over looking. but what happens is the movement isn't smooth.. and feel sticky.. press 'W' key and release keeps moving up for a few seconds and always moves to the right if you pressed 'D' key once.

With setFramerateLimit() uncommented it does keep a steady FPS.. however its still had that sticky movement. I'm bewildered..


My current code..
Main.cpp

(click to show/hide)

#include <iostream>
#include "Game.h"

using namespace std;

int main()
{
        Game game;
        game.run();
        return 0;
}
 

Game.cpp

(click to show/hide)

#include "Game.h"

Game::Game() : _Window(sf::VideoMode(640, 480), "Window"), _Player()
{
        //_Window.setFramerateLimit(FPS);

        _Player.setRadius(20.f);
        _Player.setPosition(100.f, 100.f);
        _Player.setFillColor(sf::Color::Blue);

       
}

void Game::run()
{      
        sf::Clock clock;
        sf::Time timeSinceLastUpdate = sf::Time::Zero;

        while (_Window.isOpen())
        {
                //Handle Events
                processEvents();



                sf::Time elapsedTime = clock.restart();
                timeSinceLastUpdate += elapsedTime;
                while (timeSinceLastUpdate > TimesPerFrame)// sf::Time TimesPerFrame = sf::seconds(1.f / 60.f);
                {
                        timeSinceLastUpdate -= TimesPerFrame;


                        //Game Logic
                        update(elapsedTime);

                }


                updateStatistics(elapsedTime);
                //Draw to Screen
                render();
        }
}

void Game::processEvents()
{
        sf::Event event;
        while (_Window.pollEvent(event))
        {       //Event Switch
                switch (event.type)
                {
                //Close Window
                case sf::Event::Closed:
                        _Window.close();
                        break;
                //Key Pressed
                case sf::Event::KeyPressed:
                        handlePlayerInput(event.key.code, true);
                        break;
                //Key Released
                case sf::Event::KeyReleased:
                        handlePlayerInput(event.key.code, false);
                        break;

                }
        }
}

void Game::update(sf::Time elapsedTime)
{
        sf::Vector2f movement(0.f, 0.f);
        if (_IsMovingUp)
                movement.y -= 1.f;
        if (_IsMovingDown)
                movement.y += 1.f;
        if (_IsMovingLeft)
                movement.x -= 1.f;
        if (_IsMovingRight)
                movement.x += 1.f;

        _Player.move(movement);
}

void Game::render()
{
        _Window.clear();
        _Window.draw(_Player);
        _Window.display();
}

void Game::handlePlayerInput(sf::Keyboard::Key key, bool isPressed)
{
        if (key == sf::Keyboard::W)
        {
                _IsMovingUp = isPressed;
                //cout << "W: Pressed" << isPressed << endl;
        }
        if (key == sf::Keyboard::S)
        {
                _IsMovingDown = isPressed;
                //cout << "S: Pressed" << isPressed << endl;
        }
        if (key == sf::Keyboard::A)
        {
                _IsMovingLeft = isPressed;
                //cout << "A: Pressed" << isPressed << endl;
        }
        if (key == sf::Keyboard::D)
        {
                _IsMovingDown = isPressed;
                //cout << "D: Pressed" << isPressed << endl;
        }
}

void Game::updateStatistics(sf::Time elapsedTime)
{
        _StatisticsUpdateTime += elapsedTime;
        _StatisticsNumFrames += 1;

        if (_StatisticsUpdateTime >= sf::seconds(1.0f))
        {
                system("CLS");
                cout << "Frames / Second = " << _StatisticsNumFrames << endl;
                cout << "Time / Update = " << (_StatisticsUpdateTime.asMicroseconds() / _StatisticsNumFrames) << endl;
                _StatisticsUpdateTime -= sf::seconds(1.0f);
                _StatisticsNumFrames = 0;
        }
}
 

Game.h

(click to show/hide)

using namespace std;

class Game
{
public:

        Game();
        void run();

private:

        void processEvents();
        void update(sf::Time elapsedTime);
        void render();

        void handlePlayerInput(sf::Keyboard::Key key, bool isPressed);
        void updateStatistics(sf::Time elapsedTime);

private:

        const float FPS = 60.0f;
        sf::Time TimesPerFrame = sf::seconds(1.f / 60.f);

        sf::Time _StatisticsUpdateTime;
        std::size_t _StatisticsNumFrames;

        sf::RenderWindow _Window;
        sf::CircleShape _Player;

        bool isPressed;

        bool _IsMovingUp;
        bool _IsMovingDown;
        bool _IsMovingLeft;
        bool _IsMovingRight;

};
 

Title: Re: Weird movement in my program
Post by: Jesper Juhl on August 11, 2015, 09:26:17 pm

Try something along the lines of this:

void update(sf::Time delta_time) {
  // advance the simulation - taking delta_time into account. For example:
  auto distance_to_move_this_frame = velocity * delta_time.asSeconds();
  stuff.move(distance_to_move_this_frame);
}

const sf::Time timestep = sf::seconds(1.f) / 40.f;  // take one physics step / simulation step every 1 fourtieth of a second
sf::Time remainder_time = sf::seconds(0.f);  // left over time from previous frame(s)
sf::Time elapsed_time = sf::seconds(0.f);
sf::Clock clock;
window.setFramerateLimit(60);  // render at aproximately 60 fps

while (whindow.isOpen()) {  // our main game loop
  // ... event handling goes here ...
  elapsed_time = clock.restart();  // figure out how much time passed since last frame
  elapsed_time += remainder_time;  // add the time we have left over and not yet accounted for
  while (elapsed_time >= timestep) {  // as long as enough time has passed that we need to take a step to keep up ..
    update(timestep);  // update simulation; pass in timestep so it can scale based on passed time
    elapsed_time -= timestep;  // we just took a step so subtract the time one represents
  }
  remainder_time = elapsed_time;  // whatever is left in elapsed_time is our remainder for the next frame
  window.clear();  // clear the screen in preparation for rendering the current frame
  window.draw(stuff); // render the current state of the simulation
  window.display();  // put it on the screen
}
 

The above example code has a number of advantages over what you posted above:

1) Every update advances the simulation by the exact same amount of time. This gives you reproducibility; if you replay a simulation from time T to T + N you'll always take the exact number of steps and the result after each step is deterministic (and since the update() function takes the actual value of delta_time into account it's easy to experiment with changing the timestep).

2) Updating by a fixed amount of time each step let's you guarantee such things as "my player cannot ever move entirely through a wall in a single update without me detecting it" and "I'll never overflow this calculation since I know the time/distance/whatever is always within this bound for each discreet step" etc.

3) The loop above takes as many steps as needed (or none) to catch the simulation up to real time and (crucially) it remembers the time-not-simulated-this-frame for the next one so that the simulation does not leak time and does always eventually catch up with (or at least stays close to) real-time and does not fall more and more behind.

4) it completely decouples simulation update from rendering - the two can happen at completely different intervals (as long as the simulation can keep up) and you don't depend on the actual frame rate to achieve smooth movement/simulation progress.

How you choose to step your simulation forward based on the time passed (the timestep) is up to you and how precise you want it to be of course. You can do simple Euler integration (which is not great but simple and perfectly fine for a lot of simple stuff) or you can go with Verlet or RK4 if you need more accuracy. But that's a completely different thing from keeping the timestep fixed and updating frame-rate independent and and not "leaking" time.
Also; what I present above is not perfect. It can be improved in various ways; like using the remainder_time to interpolate between the current and next frame and other tricks. But it's usually good enough for most simple (and not so simple) use cases in my experience.

I hope that made sense and was useful/helpful. If not; feel free to ask.
And if someone on the forum can find faults with the above; please do correct me.

Title: Re: Weird movement in my program
Post by: Arcade on August 11, 2015, 10:38:49 pm

Quote from: Sanction on August 11, 2015, 09:22:07 pm

and always moves to the right if you pressed 'D' key once.

Sorry if this is a dumb question, but are you sure the code you posted is the same that you are testing? I ask because looking at what you posted, it doesn't look like your player should be able to move right at all. The code makes it look like pressing D makes it move down.

if (key == sf::Keyboard::D)
    {
        _IsMovingDown = isPressed;
        ...
 

By the way, you have a several uninitialized member variables in your game class. You should initialize everything in an initialization list in your constructor (or do the C++11 equivalent if you are familiar with it). Perhaps this is the reason your player moves right.

Title: Re: Weird movement in my program
Post by: Sanction on August 11, 2015, 11:14:48 pm

Okay so Thanks to Arcade I got this sticky movement fixed. I initialize some variables and 'D' key fixed..
Arcade how would you initialize everything in an initialization list in your constructor ?

Jesper, That really help explain a lot thankyou. The FPS seems to be working correctly however it seems to gallop.. I added a sf::shape called test that just moves across the screen and he seems to gallop.. I don't know how to explain it. same with player movement.

Game.cpp

(click to show/hide)

#include "Game.h"

Game::Game() : _Window(sf::VideoMode(640, 480), "Window"), _Player()
{
        _Window.setFramerateLimit(60);

        _Player.setRadius(20.f);
        _Player.setPosition(100.f, 100.f);
        _Player.setFillColor(sf::Color::Blue);

        Test.setRadius(20.f);
        Test.setPosition(50.f, 50.f);
        Test.setFillColor(sf::Color::Green);
}

void Game::run()
{      
        sf::Clock clock;
        sf::Time timeSinceLastUpdate = sf::Time::Zero;

        while (_Window.isOpen())
        {
                //Handle Events
                processEvents();

                elapsed_time = clock.restart();
                elapsed_time += remainder_time;
                while (elapsed_time >= timestep)
                {
                        //Game Logic
                        update(timestep);
                        elapsed_time -= timestep;
                }
                remainder_time = elapsed_time;

                updateStatistics(timestep);
                //Draw to Screen
                render();
        }
}

void Game::processEvents()
{
        sf::Event event;
        while (_Window.pollEvent(event))
        {       //Event Switch
                switch (event.type)
                {
                //Close Window
                case sf::Event::Closed:
                        _Window.close();
                        break;
                //Key Pressed
                case sf::Event::KeyPressed:
                        handlePlayerInput(event.key.code, true);
                        break;
                //Key Released
                case sf::Event::KeyReleased:
                        handlePlayerInput(event.key.code, false);
                        break;

                }
        }
}

void Game::update(sf::Time deltaTime)
{
        auto distance_to_move_this_frame = velocity * deltaTime.asSeconds();

        sf::Vector2f type_of_movement(0.f, 10.f * deltaTime.asSeconds());

        sf::Vector2f movement(0.f, 0.f);
        if (_IsMovingUp)
                movement.y -= velocity;
        if (_IsMovingDown)
                movement.y += velocity;
        if (_IsMovingLeft)
                movement.x -= velocity;
        if (_IsMovingRight)
                movement.x += velocity;

        Test.move(type_of_movement);
        _Player.move(movement * deltaTime.asSeconds());
}

void Game::render()
{
        _Window.clear();
        _Window.draw(_Player);
        _Window.draw(Test);
        _Window.display();
}

void Game::handlePlayerInput(sf::Keyboard::Key key, bool isPressed)
{
        if (key == sf::Keyboard::W)
        {
                _IsMovingUp = isPressed;
        }
        if (key == sf::Keyboard::S)
        {
                _IsMovingDown = isPressed;
        }
        if (key == sf::Keyboard::A)
        {
                _IsMovingLeft = isPressed;
        }
        if (key == sf::Keyboard::D)
        {
                _IsMovingRight = isPressed;
        }
}

void Game::updateStatistics(sf::Time timestep)
{
        _StatisticsUpdateTime += timestep;
        _StatisticsNumFrames += 1;

        if (_StatisticsUpdateTime >= sf::seconds(1.0f))
        {
                system("CLS");
                cout << "Frames / Second = " << _StatisticsNumFrames << endl;
                cout << "Time / Update = " << (_StatisticsUpdateTime.asMicroseconds() / _StatisticsNumFrames) << endl;
                _StatisticsUpdateTime -= sf::seconds(1.0f);
                _StatisticsNumFrames = 0;
        }
}
 

Game.h

(click to show/hide)

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

using namespace std;

class Game
{
public:

        Game();
        void run();

private:

        void processEvents();
        void update(sf::Time deltaTime);
        void render();

        void handlePlayerInput(sf::Keyboard::Key key, bool isPressed);
        void updateStatistics(sf::Time deltaTime);

private:

        const sf::Time timestep = sf::seconds(1.f) / 40.f;
        sf::Time remainder_time = sf::seconds(0.f);
        sf::Time elapsed_time = sf::seconds(0.f);
       

        sf::Time _StatisticsUpdateTime;
        std::size_t _StatisticsNumFrames;

        sf::RenderWindow _Window;
        sf::CircleShape _Player;
        sf::CircleShape Test;

        bool isPressed = false;

        bool _IsMovingUp = false;
        bool _IsMovingDown = false;
        bool _IsMovingLeft = false;
        bool _IsMovingRight = false;

        float velocity = 100.f;

};
 

Title: Re: Weird movement in my program
Post by: Arcade on August 11, 2015, 11:33:20 pm

Quote

Arcade how would you initialize everything in an initialization list in your constructor

How you have done it in the header file is the more modern (C++11) way to initialize things and is generally fine (except you forgot _StatisticsNumFrames).

Alternatively, you could have used an initialization list in the constructor. You are actually already using the initialization list for a few things, but if you wanted to initialize all variables this way it would look like this (I did not try compiling this so there may be typos):

Game::Game()
   : _Window(sf::VideoMode(640, 480), "Window"),
      _Player(),
      timestep(sf::seconds(1.f) / 40.f),
      remainder_time(sf::seconds(0.f)),
      elapsed_time(sf::seconds(0.f)),
      _StatisticsUpdateTime(),
      _StatisticsNumFrames(0),
     isPressed(false),
    _IsMovingUp(false),
    _IsMovingDown(false),
    _IsMovingLeft(false),
    _IsMovingRight(false),
    velocity(100.f)
{
   ...
}
 

Anyway, you probably get the idea. Another thing to keep in mind is that you should order the initialization list in the same order you have the variables in the header file. You can also omit things from the initialization list that have default constructors, such as _Player, though some people argue that this is bad practice.

Title: Re: Weird movement in my program
Post by: Sanction on August 12, 2015, 12:26:38 am

I can see how this could become a mess.. could I create a like a Init_Game() function and put that into the game constructor?

Title: Re: Weird movement in my program
Post by: Jesper Juhl on August 12, 2015, 12:37:37 am

I don't mean to be offensive, but what does this have to do with SFML?
Maybe https://isocpp.org/ or a good c++ book or stackoverflow.net or some other "learn the language" site would be a better place...

Title: Re: Weird movement in my program
Post by: Sanction on August 12, 2015, 01:41:26 am

ohh naw, He suggested a good idea so I had a question about it. I do own a few C++ books and all the SFML books.. thats how I've learned C++ over the past year. Do you have any idea why the game loop has like a gallop to it?

Title: Re: Weird movement in my program
Post by: grok on August 12, 2015, 10:47:00 am

I have had non smooth movement issues unitl I implemented the idea explained in this brilliant article: http://gafferongames.com/game-physics/fix-your-timestep/

One notable step is explained there in the section "The final touch". Your code snippets above don't apply that technique, so, maybe that's why your movements yet not smooth.

Let me quote an excerpt from the article:

Quote

To understand what is going on consider a situation where the display framerate is 60fps and the physics is running at 50fps. There is no nice multiple so the accumulator causes the simulation to alternate between mostly taking one and occasionally two physics steps per-frame when the remainders “accumulate” above dt.

Now consider that in general all render frames will have some small remainder of frame time left in the accumulator that cannot be simulated because it is less than dt. What this means is that we’re displaying the state of the physics simulation at a time value slightly different from the render time. This causes a subtle but visually unpleasant stuttering of the physics simulation on the screen known as temporal aliasing.

One solution is to interpolate between the previous and current physics state based on how much time is left in the accumulator

Hope that helps.

Title: Re: Weird movement in my program
Post by: Sanction on August 12, 2015, 01:56:29 pm

I figured it out.. I was showing my FPS in command prompt but I was clearing it using system("CLS") and that created the wobble to the Game loop.

Thanks Everyone!

Title: Re: Weird movement in my program
Post by: Hapax on August 12, 2015, 07:47:13 pm

Quote from: Sanction on August 12, 2015, 01:56:29 pm

I was showing my FPS in command prompt but I was clearing it using system("CLS")

:'(

Quote from: grok on August 12, 2015, 10:47:00 am

I have had non smooth movement issues unitl I implemented the idea explained in this brilliant article: http://gafferongames.com/game-physics/fix-your-timestep/
One notable step is explained there in the section "The final touch".

The final touch does make an outstanding difference!
It took me a few reads and a break to understand it though  :-[

Title: Re: Weird movement in my program[SOLVED]
Post by: Sanction on August 17, 2015, 04:25:27 pm

I will come back to it after I learn the general grasp of using the SFML library. I do want to create some physics.

Title: Re: Weird movement in my program[SOLVED]
Post by: Hapax on August 18, 2015, 12:03:02 am

When you do your physics, make sure it's inside the timestep loop; it's a part of the update section. That way, your physics should do what you expect them to. Remember that physics are based on time so you have to be in control of your time before you can be in control of your physics  ;)

You may find my small timing library, Kairos (https://github.com/Hapaxia/Kairos/wiki), to be useful. It includes a couple of classes that help simplify timestep usage. Have a look at Timestep Lite (https://github.com/Hapaxia/Kairos/wiki/Timestep-Lite).