Build Ping Pong Game Using OpenGL and C Programming Code

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This tutorial will teach you how to create a multiplayer Ping Pong Game using C programming language, OpenGL library, and GLUT (The OpenGL Utility Toolkit).

Create a file named pingpong.c on your computer and add the following code in it.

pingpong.c

#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
#include <stdlib.h>
#include <time.h>
#include <stdlib.h>
#include <stdio.h>
/* A simple ping pong game using opengl library and glut
   The game starts on left mouse click, and stops on middle mouse click
   Player 1 can control the game using the keys q and a
   Player 2 can control the game using the keys o and l
*/

// global variables
static GLint windowSizeX = 800, windowSizeY = 1200;
static GLint orthoSizeX = 600, orthoSizeY = 400;

// game variables
static char score_1[20], score_2[20];
static GLint player1_score = 0, player2_score = 0;
static GLint player1_life = 3, player2_life = 3;
static GLint paddle_boundary = 350, paddle_height = 100, paddile_velocity = 8.0;
static GLint player1_paddile_y = 0, player2_paddile_y = 0, paddle_x = 595;
static GLfloat ball_velocity_x = 0, ball_velocity_y = 0, speed_increment = 0.5;
static GLint ball_pos_x = 0, ball_pos_y = 0, ball_radius = 20;

void init(void) {
    // initalise display with black colors
    glClearColor (0.0, 0.0, 0.0, 0.0);
    glShadeModel (GL_FLAT);

    srand(time(NULL));   // should only be called once
}

// draw text on screen
void drawStrokeText(char*string, int x, int y, int z)
{
    char *c;
    glPushMatrix();
    glTranslatef(x, y+8,z);
    // glScalef(0.09f,-0.08f,z);
    for (c=string; *c != '\0'; c++)
    {
        glutStrokeCharacter(GLUT_STROKE_ROMAN , *c);
    }
    glPopMatrix();
}

// draw the center lines spaces 20 pixels apart and with a width of 4 px
void drawCenterLines() {
    // center lines start
    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , -410);
    glVertex2f(2 , -410);
    glVertex2f(2 , -390);
    glVertex2f(-2 , -390);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , -370);
    glVertex2f(2 , -370);
    glVertex2f(2 , -350);
    glVertex2f(-2 , -350);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , -330);
    glVertex2f(2 , -330);
    glVertex2f(2 , -310);
    glVertex2f(-2 , -310);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , -290);
    glVertex2f(2 , -290);
    glVertex2f(2 , -270);
    glVertex2f(-2 , -270);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , -250);
    glVertex2f(2 , -250);
    glVertex2f(2 , -230);
    glVertex2f(-2 , -230);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , -210);
    glVertex2f(2 , -210);
    glVertex2f(2 , -190);
    glVertex2f(-2 , -190);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , -170);
    glVertex2f(2 , -170);
    glVertex2f(2 , -150);
    glVertex2f(-2 , -150);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , -130);
    glVertex2f(2 , -130);
    glVertex2f(2 , -110);
    glVertex2f(-2 , -110);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , -90);
    glVertex2f(2 , -90);
    glVertex2f(2 , -70);
    glVertex2f(-2 , -70);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , -50);
    glVertex2f(2 , -50);
    glVertex2f(2 , -30);
    glVertex2f(-2 , -30);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , -10);
    glVertex2f(2 , -10);
    glVertex2f(2 , 10);
    glVertex2f(-2 , 10);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , 30);
    glVertex2f(2 , 30);
    glVertex2f(2 , 50);
    glVertex2f(-2 , 50);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , 70);
    glVertex2f(2 , 70);
    glVertex2f(2 , 90);
    glVertex2f(-2 , 90);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , 110);
    glVertex2f(2 , 110);
    glVertex2f(2 , 130);
    glVertex2f(-2 , 130);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , 150);
    glVertex2f(2 , 150);
    glVertex2f(2 , 170);
    glVertex2f(-2 , 170);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , 190);
    glVertex2f(2 , 190);
    glVertex2f(2 , 210);
    glVertex2f(-2 , 210);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , 230);
    glVertex2f(2 , 230);
    glVertex2f(2 , 250);
    glVertex2f(-2 , 250);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , 270);
    glVertex2f(2 , 270);
    glVertex2f(2 , 290);
    glVertex2f(-2 , 290);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , 310);
    glVertex2f(2 , 310);
    glVertex2f(2 , 330);
    glVertex2f(-2 , 330);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , 350);
    glVertex2f(2 , 350);
    glVertex2f(2 , 370);
    glVertex2f(-2 , 370);
    glEnd();

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    glVertex2f(-2 , 390);
    glVertex2f(2 , 390);
    glVertex2f(2 , 410);
    glVertex2f(-2 , 410);
    glEnd();
    // center lines end
}

// x, y is the top left corodinate of the paddle
void drawPaddle(int x, int y) {
    glPushMatrix();

    glTranslatef(x, y, 0);

    glBegin(GL_QUADS);
    glColor3f(1.0, 1.0, 1.0);
    int height = paddle_height / 2;
    glVertex2f(-5 , height);
    glVertex2f(5 , height);
    glVertex2f(5 , -height);
    glVertex2f(-5, -height);
    glEnd();

    glPopMatrix();
}

void drawBall(int x, int y) {
    glPushMatrix();

    glTranslatef(x, y, 0);
    glColor3f(1.0, 1.0, 1.0);
    glutSolidSphere (ball_radius, 20, 16);

    glPopMatrix();
}

// main display functions
void display(void) {
    glClear(GL_COLOR_BUFFER_BIT);

    // create center lines
    drawCenterLines();

    // draw left paddle at (-paddle_x, player1_paddile_y)
    drawPaddle(-paddle_x, player1_paddile_y);
    // draw right paddle at (paddle_x, player2_paddile_y)
    drawPaddle(paddle_x, player2_paddile_y);

    // draw the ball (ball_pos_x, ball_pos_y) - varies in each frame
    drawBall(ball_pos_x, ball_pos_y);

    // draw the score on the left for player 1
    snprintf (score_1, sizeof(score_1), "%d", player1_score);
    drawStrokeText(score_1, -300, 200, 0);

    // draw the score on the left for player 1
    snprintf (score_2, sizeof(score_2), "%d", player2_score);
    drawStrokeText(score_2, 200, 200, 0);

    // swap the current frame with the drawn frame
    glutSwapBuffers();
    glFlush();
}

void startGame(void) {

    // move the ball
    ball_pos_x += ball_velocity_x;
    ball_pos_y += ball_velocity_y;

    // ball hits the top or bottom
    if (ball_pos_y + ball_radius > orthoSizeY || ball_pos_y - ball_radius < -orthoSizeY)
        ball_velocity_y = -ball_velocity_y;

    // ball hits the left paddle
    if (ball_pos_x - ball_radius - 5 < -paddle_x && ball_pos_x - ball_radius < -paddle_x)
        if (ball_pos_y < player1_paddile_y + paddle_height && ball_pos_y > player1_paddile_y - paddle_height) {
            ball_velocity_x = -ball_velocity_x;
            ball_velocity_x += speed_increment;
            paddile_velocity += speed_increment;
        }


    // ball hits the right paddle
    if (ball_pos_x + ball_radius + 5 > paddle_x && ball_pos_x + ball_radius < paddle_x)
        if (ball_pos_y < player2_paddile_y + paddle_height && ball_pos_y > player2_paddile_y - paddle_height)
            ball_velocity_x = -ball_velocity_x;

    // player 1 scores
    if (ball_pos_x + ball_radius > orthoSizeX) {
        player1_score++;
        printf("Player 1 = %d \n", player1_score);
        ball_velocity_x = -ball_velocity_x;
    }

    // player 2 scores
    if (ball_pos_x - ball_radius < -orthoSizeX) {
        player2_score++;
        printf("Player 2 = %d \n", player2_score);
        ball_velocity_x = -ball_velocity_x;
    }

    glutPostRedisplay();
}

// reshape the display
void reshape(int w, int h) {
    glViewport (0, 0, (GLsizei) w, (GLsizei) h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-orthoSizeX, orthoSizeX, -orthoSizeY, orthoSizeY, -100, 100);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

// on mouse button click
void mouse(int button, int state, int x, int y) {
    switch (button) {
        // left button - initialize random velocity between (ran(5) - rand(3))
        case GLUT_LEFT_BUTTON:
            if (state == GLUT_DOWN)
            ball_velocity_x = (rand() % 5) -  (rand() % 3);
            ball_velocity_y = (rand() % 5) -  (rand() % 3);

            // keep on calling the callback to move the ball and check boundary conditions
            glutIdleFunc(startGame);
            break;
        // middle button to reset the ball, paddle and score
        case GLUT_MIDDLE_BUTTON:
            // reset ball, paddle and player scores
            ball_pos_x = ball_pos_y = 0;
            player1_paddile_y = player2_paddile_y = 0;
            player1_score = player2_score = 0;
            if (state == GLUT_DOWN)
                // remove the call back so that game stops
                glutIdleFunc(NULL);
            break;
        default:
        break;
    }
}


void keyboard (unsigned char key, int x, int y) {
    switch (key) {
        // move player 1 paddile up
        case 'q':
            if (player1_paddile_y < paddle_boundary)
                player1_paddile_y += paddile_velocity;
            glutPostRedisplay();
            break;
        // move player 1 paddile down
        case 'a':
            if (player1_paddile_y > -paddle_boundary)
                player1_paddile_y -= paddile_velocity;
            glutPostRedisplay();
            break;
        // move player 2 paddile up
        case 'o':
            if (player2_paddile_y < paddle_boundary)
                player2_paddile_y += paddile_velocity;
            glutPostRedisplay();
            break;
        // move player 2 paddile down
        case 'l':
            if (player2_paddile_y > -paddle_boundary)
                player2_paddile_y -= paddile_velocity;
            glutPostRedisplay();
            break;
        // exit on esc
        case 27:
            exit(0);
            break;
        default:
            break;
    }
}

/*
* Request double buffer display mode.
* Register mouse input callback functions
*/
int main(int argc, char** argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize (1200, 800);
    glutInitWindowPosition (10, 10);
    glutCreateWindow (argv[0]);
    init ();

    // call back functions for rendering, reshape
    glutDisplayFunc(display);
    glutReshapeFunc(reshape);

    // callback on mouse click and keyboard input
    glutMouseFunc(mouse);
    glutKeyboardFunc(keyboard);
    glutMainLoop();
    return 0;
}

Run the Program

$ gcc pingpong.c  -lm -lglut -lGL -lGLU

How to Play this Ping Pong Game?

To start playing the game you have to click the left mouse button whereas press the middle mouse button to stop it.


How to Control Player 1?

Move Up: Q

Move Down: A


How to Control Player 2?

Move Up: O

Move Down: L


How to Restart Ping Pong Game?

Press the middle mouse button to reset the ball, paddle and score.

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