Bounce Logic Problem

[giblit]

I just can't seem to figure out what is wrong with my logic. It works fine when it bounces off the bottom or top but when it hits a side it flips out.

#include <SFML/Graphics.hpp> //sf::RenderWindow
#include <SFML/Window.hpp> //sf::VideoMode, sf::Event
#include <cmath> //sinf
#include <chrono>
#include <random>

int main()
{
    const int ScreenWidth = 640 , ScreenHeight = 400 , BPP = 32;
    const std::string Title = "Bouncing Square";
    sf::RenderWindow Window( sf::VideoMode( ScreenWidth , ScreenHeight , BPP ) , Title );
    sf::Event Event;

    const int Width = 15;
    sf::RectangleShape Square( {Width , Width} );
    Square.setOrigin( Width/2.0f , Width/2.0f ); //centered
    Square.setPosition( ScreenWidth/2.0f , ScreenHeight/2.0f );

    sf::FloatRect Rect;
    sf::Clock Clock;
    float DeltaTime;
    float Velocity = 100.0f;
    auto Seed = std::chrono::high_resolution_clock::now().time_since_epoch().count();
    std::mt19937 RandomGen( Seed );
    float Angle = static_cast<float>( RandomGen() % 360 );
    float UnitsToMoveX , UnitsToMoveY;
    const float Pi = 3.14159f;
    const float Radian = Pi / 180.0f;


    while( Window.isOpen() )
    {
        Window.clear();
        DeltaTime = Clock.restart().asSeconds();
        UnitsToMoveY = sinf( Angle * Radian ) * DeltaTime * Velocity;
        UnitsToMoveX = cosf( Angle * Radian ) * DeltaTime * Velocity;
        Rect = Square.getGlobalBounds();

        //Hit wall
        if( Rect.top + UnitsToMoveY <= 0.0f || Rect.top + Rect.height + UnitsToMoveY >= ScreenHeight )
        {
            Angle = 360 - Angle;
            UnitsToMoveY = -UnitsToMoveY; //Flip the movement (bounce)
            Velocity += 5.0f; //increase velocity
        }

        else if( Rect.left + UnitsToMoveX <= 0.0f || Rect.left + Rect.width + UnitsToMoveX >= ScreenWidth )
        {
            Angle = 360 - Angle;
            UnitsToMoveX = -UnitsToMoveX; //Flip the movement (bounce)
            Velocity += 5.0f; //increase velocity
        }


        Square.move( UnitsToMoveX , UnitsToMoveY );
        Window.draw( Square );
        Window.display();

        while( Window.pollEvent( Event ) )
        {
            if( Event.type == sf::Event::Closed )
                Window.close();
        }
    }
}

The logic that seems to be completely messed up is this part:

//if it doesn't hit top/bottom check sides
        else if( Rect.left + UnitsToMoveX <= 0.0f || Rect.left + Rect.width + UnitsToMoveX >= ScreenWidth )
        {
            Angle = 360 - Angle;
            UnitsToMoveX = -UnitsToMoveX; //Flip the movement (bounce)
            Velocity += 5.0f; //increase velocity
        }

The logic seems right to me.

The Rect is made of the Left , Top , Width , and Height of the Square
The Origin is the center of the Square so x = left - width / 2 , y = top - height / 2

And my if statement says:
if the Left edge of the box moves left X units and is less than or equal to 0 ( left wall ) or if the right edge ( left + width ) + X Units is greater than or equal to the Width of the window ( right wall ) then flip the angle and movement ( x axis ) and increase the velocity of the object.

But I must have messed up somewhere so if a second pair of eyes could help me out I would appreciate it greatly.


PS sorry if the code is pretty messy I was trying to quickly throw together an example of what my problem was in one file.

*edit I also tried:

if( Square.getPosition().x + UnitsToMoveX - Width / 2.0 <= 0.0 || Square.getPosition().x + UnitsToMoveX + Width / 2.0 >= ScreenWidth ) Same exact problem though

One more thing I am using floats instead of doubles because the precision isn't very important or at least I didn't think it was with these variables.

[ne555]

        else if( Rect.left + UnitsToMoveX <= 0.0f || Rect.left + Rect.width + UnitsToMoveX >= ScreenWidth )
        {
            //Angle = 360 - Angle;
            Angle = 180 - Angle;
            UnitsToMoveX = -UnitsToMoveX; //Flip the movement (bounce)
            Velocity += 5.0f; //increase velocity
        }

[giblit]

Wow that works. I think I need to work on my math a bit better. To see why the bounce formula differs from hitting a side wall to a top/bottom wall.

Thanks ne555