LAB 2B

BIT20203: Graphics Programming

LAB SHEET 3

Title                          : Graphics Programming using OpenGL

Objectives           : At the end of the session, students are able to:

                                          i.         Create a bare bone program.

                                         ii.         Create a keyboard event callback

                                       iii.         Customizing the window

                                        iv.         Draw a 2D triangle

Duration               : 2 Hours

Tasks                       :

1.     Write the following code. Compile and run.

      i.         Creating a bare bone program

/* ex1.c */

#include <GL/glut.h>

void display (void) {

/* Called when OpenGL needs to update the display */

glClear (GL_COLOR_BUFFER_BIT); /* Clear the window */

glFlush(); /* Force update of screen */

}

int main (int argc, char **argv) {

glutInit (&argc, argv); /* Initialise OpenGL */

glutCreateWindow ("ex1"); /* Create the window */

glutDisplayFunc (display); /* Register the "display" function */

glutMainLoop (); /* Enter the OpenGL main loop */

return 0;

}

/* end of ex1.c */

     ii.         Keyboard event callback

/* ex2.c */

#include <stdio.h>

#include <GL/glut.h>

void display (void) {

/* Called when OpenGL needs to update the display */

glClear (GL_COLOR_BUFFER_BIT); /* Clear the window */

glFlush(); /* Force update of screen */

}

void keyboard (unsigned char key, int x, int y) {

/* Called when a key is pressed */

if (key == 27) exit (0); /* 27 is the Escape key */

else printf ("You pressed %c\n", key);

}

int main(int argc, char **argv) {

glutInit (&argc, argv); /* Initialise OpenGL */

glutCreateWindow ("ex2"); /* Create the window */

glutDisplayFunc (display); /* Register the "display" function */

glutKeyboardFunc (keyboard); /* Register the "keyboard" function */

glutMainLoop (); /* Enter the OpenGL main loop */

return 0;

}

/*end of ex2.c */

   iii.         Customizing the windows

/* ex3.c */

#include <GL/glut.h>

void display (void) {

/* Called when OpenGL needs to update the display */

glClearColor (1.0,1.0,1.0,0.0);

glClear (GL_COLOR_BUFFER_BIT); /* Clear the window */

glFlush(); /* Force update of screen */

}

void keyboard (unsigned char key, int x, int y) {

/* Called when a key is pressed */

if (key == 27) exit (0); /* 27 is the Escape key */

}

int main(int argc, char **argv) {

glutInit (&argc, argv); /* Initialise OpenGL */

glutInitWindowSize (500, 500); /* Set the window size */

glutInitWindowPosition (100, 100); /* Set the window position */

glutCreateWindow ("ex3"); /* Create the window */

glutDisplayFunc (display); /* Register the "display" function */

glutKeyboardFunc (keyboard); /* Register the "keyboard" function */

glutMainLoop (); /* Enter the OpenGL main loop */

return 0;

}

/* end of ex3.c */

    iv.         Draw a 2D triangle

ex4.c draws a triangle, using the coordinates shown in the figure below

Here’s the code:

/* ex4.c */

#include <GL/glut.h>

void display (void) {

/* Called when OpenGL needs to update the display */

glClear (GL_COLOR_BUFFER_BIT); /* Clear the window */

glLoadIdentity ();

gluLookAt (0.0, 0.0, 0.5, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

glBegin (GL_LINE_LOOP); /* Draw a triangle */

glVertex3f(-0.3, -0.3, 0.0);

glVertex3f(0.0, 0.3, 0.0);

glVertex3f(0.3, -0.3, 0.0);

glEnd();

glFlush(); /* Force update of screen */

}

void keyboard (unsigned char key, int x, int y) {

/* Called when a key is pressed */

if (key == 27) exit (0); /* 27 is the Escape key */

}

void reshape (int width, int height)

{ /* Called when the window is created, moved or resized */

glViewport (0, 0, (GLsizei) width, (GLsizei) height);

glMatrixMode (GL_PROJECTION); /* Select the projection matrix */

glLoadIdentity (); /* Initialise it */

glOrtho(-1.0,1.0, -1.0,1.0, -1.0,1.0); /* The unit cube */

glMatrixMode (GL_MODELVIEW); /* Select the modelview matrix */

}

int main(int argc, char **argv) {

glutInit (&argc, argv); /* Initialise OpenGL */

glutInitWindowSize (500, 500); /* Set the window size */

glutInitWindowPosition (100, 100); /* Set the window position */

glutCreateWindow ("ex4"); /* Create the window */

glutDisplayFunc (display); /* Register the "display" function */

glutReshapeFunc (reshape); /* Register the "reshape" function */

glutKeyboardFunc (keyboard); /* Register the "keyboard" function */

glutMainLoop (); /* Enter the OpenGL main loop */

return 0;

}

/* end of ex4.c */

2.     Write program with the following specification:

      i.         Windows size : 800 x 600

     ii.         Windows title: My OpenGL Program

   iii.         Draw a star

    iv.         Submit your code 1 week  after your lab session.

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