SDL_pong

[ETAkoG1T]

The rand() pard doesn't work properly, the ball often just bounces infinitely up and down in the middle and sometimes it gets stuck not moving (in the middle). Code mostly stolen from NomNomNom069 on youtube.

code:

#include "SDL.h"
#include "SDL_ttf.h"
#include <sstream>
const int BALL_X = 390;
const int BALL_Y = 290;
using namespace std;

SDL_Surface * screen;
SDL_Event occur;
Uint32 white;
SDL_Color Pink = {255, 0, 255};
SDL_Rect PlayerPaddle;
SDL_Rect AIPaddle;
SDL_Rect Ball;
TTF_Font *times;
SDL_Rect Player_score1, AI_score1;


SDL_Surface *P_score;
SDL_Surface *A_score;




#include <stdlib.h>
#include <ctime>
int GetRandomNumber(int high, int low);
bool PointInRect(int x, int y, SDL_Rect rec);
bool CheckCollision(SDL_Rect r1, SDL_Rect r2);

int xVel, yVel;
int Player = 0, AI = 0;

void ResetBall()
{
	Ball.x = BALL_X;
	Ball.y = BALL_Y;

	xVel = GetRandomNumber(4, -2);
	yVel = GetRandomNumber(4, -2);
}

int GetRandomNumber(int high, int low)
{
	return rand()%high+low;
}

void LoadGame()
{
	SDL_Init(SDL_INIT_EVERYTHING);
	TTF_Init();
	SDL_WM_SetCaption("Pong", NULL);
	screen = SDL_SetVideoMode(800, 600, 32, SDL_HWSURFACE);

	PlayerPaddle.x = 20;
	PlayerPaddle.y = 250;
	PlayerPaddle.h = 100;
	PlayerPaddle.w = 20;

	AIPaddle.x = 760;
	AIPaddle.y = 250;
	AIPaddle.h = 100;
	AIPaddle.w = 20;

	Ball.x = BALL_X;
	Ball.y = BALL_Y;
	Ball.w = 20;
	Ball.h = 20;

	white = SDL_MapRGB(screen->format, 255, 255, 255);

	srand(time(NULL));

	ResetBall();

	times = TTF_OpenFont("Times.ttf", 14);

	Player_score1.x = 50;
	AI_score1.x = 725;
}

void Logic()
{
	Uint8 *keystates = SDL_GetKeyState(NULL);

	if(keystates[SDLK_w])
	{
		PlayerPaddle.y -= 1;
	}
	if(keystates[SDLK_s])
	{
		PlayerPaddle.y += 1;
	}

	if(PlayerPaddle.y < 1)
	{
		PlayerPaddle.y = 1;
	}

	if(PlayerPaddle.y + PlayerPaddle.h > 599)
	{
		PlayerPaddle.y = 599 - PlayerPaddle.h;
	}

	
	if(AIPaddle.y < 1)
	{
		AIPaddle.y = 1;
	}

	if(AIPaddle.y + AIPaddle.h > 599)
	{
		AIPaddle.y = 599 - AIPaddle.h;
	}


	if(AIPaddle.y + 0.5 * AIPaddle.h > Ball.y + 0.5 * Ball.h)
	{
		AIPaddle.y--;
	}

	if(AIPaddle.y + 0.5 * AIPaddle.h < Ball.y + 0.5 * Ball.h)
	{
		AIPaddle.y++;
	}

	Ball.x += xVel;
	Ball.y += yVel;

	if(Ball.y < 1)
	{
		yVel = -yVel;
	}

	if(Ball.y + Ball.h > 599)
	{
		yVel = -yVel;
	}

	if(Ball.x < 2)
	{
		ResetBall();
		AI++;

	}

	if(Ball.x + Ball.w > 798)
	{
		ResetBall();
		Player++;
	}

	if(CheckCollision(Ball, PlayerPaddle) == true)
	{
		xVel = -xVel;
	}

	if(CheckCollision(Ball, AIPaddle) == true)
	{
		xVel = -xVel;
	}
}

void DrawScreen()
{
	SDL_FillRect(screen, NULL, 0);


	SDL_FillRect(screen, &PlayerPaddle, white);
	SDL_FillRect(screen, &AIPaddle, white);
	SDL_FillRect(screen, &Ball, white);
	stringstream Pscore;
	stringstream Ascore;

	Ascore << AI;
	Pscore << Player;

	SDL_Surface *Player_score = TTF_RenderText_Solid(times, Pscore.str().c_str(), Pink);
	SDL_Surface *AI_score = TTF_RenderText_Solid(times, Ascore.str().c_str(), Pink);
	
	SDL_BlitSurface(Player_score, NULL, screen, &Player_score1);
	SDL_BlitSurface(AI_score, NULL, screen, &AI_score1);

	SDL_Flip(screen);

	SDL_FreeSurface(Player_score);
	SDL_FreeSurface(AI_score);
}

void Quit()
{
	TTF_CloseFont(times);
	TTF_Quit();
	SDL_Quit();
}

bool PointInRect(int x, int y, SDL_Rect rec)
{
	if(x > rec.x && y > rec.y && x < rec.x + rec.w && y < rec.y + rec.h)
	{
		return true;
	}
	else
		return false;
}

bool CheckCollision(SDL_Rect r1, SDL_Rect r2)
{
	if(PointInRect(r1.x, r1.y, r2) == true ||
		PointInRect(r1.x + r1.w, r1.y, r2) == true ||
		PointInRect(r1.x, r1.y + r1.h, r2) == true ||
		PointInRect(r1.x + r1.w, r1.y + r1.h, r2) == true)
	{
		return true;
	}

	else 
		return false;
}

int main(int argc, char *args[])
{

	LoadGame();
	bool running = true;

	while( running == true )
	{
		SDL_PollEvent(&occur);
		
		if(occur.type == SDL_QUIT)
		{
			running = false;
		}
		Logic();
		DrawScreen();
	}

	Quit();
	return 0;
}

[Peter87]

You have to make sure the xVel != 0 because otherwise the ball will never reach any of the paddles.

[ETAkoG1T]

Thank you =) Do I have to check yVel to?

EDIT:
Was this a decent solution :) I think it was a good idea to do it this way:

void ResetBall()
{
	Ball.x = BALL_X;
	Ball.y = BALL_Y;

	xVel = 0, yVel = 0;
	
	while(xVel == 0 || yVel == 0)
	{
		xVel = GetRandomNumber(2, -2);
		yVel = GetRandomNumber(2, -2);
	}
}