Write a complete OpenGL program to demonstrate animation effects on a simple object.

Write a complete OpenGL program to demonstrate animation effects on a simple object.

Answer:-

simple OpenGL program that demonstrates basic animation effects using a rotating square

#include <GL/glut.h>  // Include the GLUT header for OpenGL utilities

// Rotation angle
float angle = 0.0;

// Function to display the scene
void display() {
    // Clear the color buffer
    glClear(GL_COLOR_BUFFER_BIT);

    // Load the identity matrix
    glLoadIdentity();

    // Move the object to the center of the window
    glTranslatef(0.0, 0.0, -5.0);

    // Rotate the object
    glRotatef(angle, 0.0, 1.0, 0.0);

    // Draw a simple square (a 2D object) in the center
    glBegin(GL_QUADS);
        glColor3f(1.0, 0.0, 0.0);  // Red color
        glVertex2f(-1.0, 1.0);
        glVertex2f(1.0, 1.0);
        glVertex2f(1.0, -1.0);
        glVertex2f(-1.0, -1.0);
    glEnd();

    // Swap the front and back buffers
    glutSwapBuffers();
}

// Function to update the animation
void update(int value) {
    angle += 2.0;  // Increment the angle
    if (angle > 360) {
        angle -= 360;  // Keep the angle within 0-360 degrees
    }

    glutPostRedisplay();  // Request a redraw
    glutTimerFunc(16, update, 0);  // Call update() again after 16 milliseconds (60 FPS)
}

// Function to initialize OpenGL settings
void init() {
    glClearColor(0.0, 0.0, 0.0, 1.0);  // Set the background color to black
    glMatrixMode(GL_PROJECTION);  // Set the projection matrix mode
    gluOrtho2D(-2.0, 2.0, -2.0, 2.0);  // Set the orthographic projection
}

// Main function
int main(int argc, char **argv) {
    glutInit(&argc, argv);  // Initialize GLUT
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);  // Set display mode
    glutInitWindowSize(500, 500);  // Set window size
    glutCreateWindow("Simple Animation");  // Create window with title

    init();  // Initialize OpenGL settings
    glutDisplayFunc(display);  // Register display function
    glutTimerFunc(25, update, 0);  // Set up the timer function for animation

    glutMainLoop();  // Enter the GLUT event processing loop
    return 0;
}

Explanation

1. Initialization:
   • glutInit(): Initializes GLUT.
   • glutInitDisplayMode(): Sets the display mode to double buffering and RGB color.
   • glutInitWindowSize(): Sets the size of the window.
   • glutCreateWindow(): Creates a window with the specified title.
   • init(): Sets up the background color and projection.
2. Display Function (display):
   • Clears the screen.
   • Translates and rotates the object.
   • Draws a red square.
   • Swaps buffers to update the display.
3. Update Function (update):
   • Updates the rotation angle.
   • Requests a redraw.
   • Sets up a timer to call itself again after 16 milliseconds (for 60 FPS).
4. Main Loop:
   • Registers the display and timer functions.
   • Enters the GLUT event processing loop.

This code will create a window displaying a rotating red square, demonstrating basic animation effects using OpenGL.