Bouncing Ball Collision -SFML-CodePudding

I'm making a simple simulation of a ball bouncing. I already implemented gravity, but I don't know how to handle for collisions (make the ball change direction). I tried reverting the velocity, but that didn't work.

// random start velocity
float v = 2.f;

// force
float f = 0.f   (v*t)   (1/2.f)*G*t;

std::cout << f << "\n";

// collision happened
if ((ball.getPosition().y   ball.getRadius()) > 400.f) {
    // revert the velocity
    v = -v;
}

ball.setPosition(sf::Vector2f(ball.getPosition().x, f));

Here is the full code:

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

//calculate the distance between the ball and    the ground
float distance_to_ground(float ball_y, float ground_y){
    return (float)(ball_y - ground_y);
}

int main() {
    // gravity constant
    const float G = 9.807;

    // create the window
    sf::RenderWindow window(sf::VideoMode(800, 600), "My window");
    window.setFramerateLimit(60);

    sf::CircleShape ball(30);
    ball.setPosition(window.getSize().x/2.f, 100);
    ball.setOrigin(ball.getRadius(),ball.getRadius());

    //mass of the ball
    const float m1 = ball.getRadius();

    sf::Clock TimeDelta;
    // run the program as long as the window is open
    while (window.isOpen())
    {
        // check all the window's events that were triggered since the last iteration of the loop
        sf::Event event;
        while (window.pollEvent(event))
        {
            // "close requested" event: we close the window
            if (event.type == sf::Event::Closed)
                window.close();
        }

        sf::Time elapsed = TimeDelta.getElapsedTime();
        float t = elapsed.asSeconds();

        // distance between the ball and the ground
        float R = distance_to_ground(ball.getPosition().y, window.getSize().y);

        // random start velocity
        float v = 2.f;

        // force
        float f = 0.f   (v*t)   (1/2.f)*G*t;

        std::cout << f << "\n";

        // collision happened
        if ((ball.getPosition().y   ball.getRadius()) > 400.f){
            // change the velocity to negative
            v = -v;
        }

        ball.setPosition(sf::Vector2f(ball.getPosition().x, f));

        // clear the window with black color
        window.clear(sf::Color::Black);

        // draw everything here...
        window.draw(ball);

        // end the current frame
        window.display();
    }
    return 0;
}

CodePudding user response：

//collision happened
if ((ball.getPosition().y   ball.getRadius()) > 400.f){
    // revert the velocity 
    v = -v;
}

This can result in the ball bouncing up and down, and falling through. You need:

//collision happened
if ((ball.getPosition().y   ball.getRadius()) > 400.f){
    // make sure the velocity is downwards.
    v = -std::abs(v);
}