Describe the basic structure of an OpenGL graphics program, including necessary OpenGL functions.

2.A] Describe the basic structure of an OpenGL graphics program, including necessary OpenGL functions.

Answer:-

Basic Structure of an OpenGL Graphics Program Using GLUT

1. Initialize the Program

Include Headers:

#include <GL/glut.h>  // GLUT library for managing windows and input

Initialize GLUT:

glutInit(&argc, argv);  // Prepare GLUT

Set Display Mode and Create Window:

glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);  // Use single buffer and RGB color
glutInitWindowSize(800, 600);  // Define window size
glutCreateWindow("OpenGL Window");  // Create the window

2. Define What to Draw

Create Display Function:

void display() {
    glClear(GL_COLOR_BUFFER_BIT);  // Clear the screen

    glBegin(GL_TRIANGLES);  // Start drawing a triangle
        glVertex2f(-0.5f, -0.5f);  // Bottom-left vertex
        glVertex2f( 0.5f, -0.5f);  // Bottom-right vertex
        glVertex2f( 0.0f,  0.5f);  // Top vertex
    glEnd();  // Finish drawing

    glFlush();  // Ensure commands are executed
}

Register Display Function:

glutDisplayFunc(display);  // Tell GLUT to call 'display' when needed

3. Main Loop

Start Main Loop:

glutMainLoop();  // Start event processing loop

4. Optional: Handle Input

Handle Keyboard Input:

void handleKeys(unsigned char key, int x, int y) {
    if (key == 27) {  // ESC key
        exit(0);  // Exit the program
    }
}
glutKeyboardFunc(handleKeys);  // Register the keyboard handler

Summary of Functions:

• glutInit: Initializes GLUT.
• glutInitDisplayMode: Sets the display mode.
• glutInitWindowSize: Defines the window size.
• glutCreateWindow: Creates a window.
• glutDisplayFunc: Registers the display function.
• glutMainLoop: Starts the GLUT event loop.
• glClear: Clears the screen.
• glBegin/glEnd: Defines the shape (e.g., a triangle).
• glVertex2f: Specifies vertex coordinates.
• glFlush: Executes drawing commands.
• glutKeyboardFunc: Handles keyboard input.