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Help => General => Topic started by: The New Guy on April 17, 2015, 04:53:40 am

Title: Newbie Time-Based Movement Question
Post by: The New Guy on April 17, 2015, 04:53:40 am

Hey all,

Newbie game development programmer here, trying to figure out why my movement is so choppy. I have implemented the time-base movement that I see from so many examples.

I cant find what I am doing wrong here. Any help would be appreciated!

Code: [Select]

#include <SFML/Graphics.hpp>
#include "AssetManager.h"
#include "Animator.h"
#include <SFML\Audio.hpp>
#include<SFML\System.hpp>
#include <iostream>
#include <SFML\Network.hpp>

using namespace sf;

int main()
{

RenderWindow window(VideoMode(800,600),"Pong");
window.setFramerateLimit(60);
AssetManager manager;



Sprite player1(AssetManager::GetTexture("pong.png"));
Sprite aiPaddle(AssetManager::GetTexture("pong.png"));
Sprite ball(AssetManager::GetTexture("ball.png"));

player1.setPosition(100,300);
int player1Speed =5;
aiPaddle.setPosition(700,300);
int ai1Speed =5;
ball.setPosition(400,300);
float ballSpeed = 100.f;

player1.setOrigin(player1.getTextureRect().width/2,player1.getTextureRect().height/2);
aiPaddle.setOrigin(aiPaddle.getTextureRect().width/2,aiPaddle.getTextureRect().height/2);
ball.setOrigin(ball.getTextureRect().width/2,ball.getTextureRect().height/2);

Clock clock;
Time timeSinceLastUpdate = Time::Zero;
Time TimePerFrame =seconds(1.f/60.f);

while(window.isOpen())
{
Event ev;

Vector2f movement;
timeSinceLastUpdate += clock.restart();



while(timeSinceLastUpdate > TimePerFrame)
{
while(window.pollEvent(ev))
{
switch(ev.type)
{
case Event::EventType::KeyPressed:
if(ev.key.code == Keyboard::Key::Up)
{
movement.y -= -100.f;
}
if(ev.key.code == Keyboard::Key::Down)
{
movement.y -= 100.f;
}

break;
default:
break;
}
}
timeSinceLastUpdate -=TimePerFrame;
player1.move(movement * timeSinceLastUpdate.asSeconds());
ball.move(ballSpeed*timeSinceLastUpdate.asSeconds(),ballSpeed*timeSinceLastUpdate.asSeconds());
if(aiPaddle.getPosition().y < ball.getPosition().y)
{
aiPaddle.move(0,100*timeSinceLastUpdate.asSeconds());
}
if(aiPaddle.getPosition().y > ball.getPosition().y)
{
aiPaddle.move(0,-100*timeSinceLastUpdate.asSeconds());
}
if(aiPaddle.getGlobalBounds().intersects(ball.getGlobalBounds()))
{
ballSpeed *=-1;
}
if(player1.getGlobalBounds().intersects(ball.getGlobalBounds()))
{
ballSpeed *=-1;
}
}
window.clear(Color::White);
window.draw(player1);
window.draw(aiPaddle);
window.draw(ball);
window.display();

}

}


Title: Re: Newbie Time-Based Movement Question
Post by: dabbertorres on April 17, 2015, 07:56:32 am

You're using the wrong time value for moving the sprites. You should be using TimePerFrame (which stays constant, which is needed for the smooth movement you want (I'd also make it 'const' to show that)), not timeSinceLastUpdate (which gets progressively smaller).

Title: Re: Newbie Time-Based Movement Question
Post by: smguyk on April 18, 2015, 02:12:28 pm

1. You are using Event::EventType::KeyPressed and the events will only fire when they are polled. For real time input you should be using sf::Keyboard::isKeyPressed

2. Move your whole while(window.pollEvent(ev)) loop out of the while(timeSinceLastUpdate > TimePerFrame) loop. Only physics updates, real time input handling etc. should be in that one.. not events

Title: Re: Newbie Time-Based Movement Question
Post by: The New Guy on April 20, 2015, 08:06:42 pm

Thanks for the advice!

I will try this out tonight.

-Austin