square-in-square-animation.cpp

#include <GLUT/GLUT.h>
#include <OpenGL/OpenGL.h>
#include <math.h>
#include <stdio.h>

float x1=-2.0, x2=2.0;
float x = 0.7, y = 0.7;

void keyPressed(int key, int x1, int y1)
{
    if(key==GLUT_KEY_UP)
    {
        x *= 1.35;
        y *= 1.35;
        glutPostRedisplay();
    }
    if(key==GLUT_KEY_DOWN)
    {
        x *= 0.95;
        y *= 0.95;
        glutPostRedisplay();
    }
}

void drawSquare(float x, float y) {
    glColor3f(0.8, 0.7, 0.7);
    glBegin(GL_LINES);
    glVertex2f(x, 0.0);
    glVertex2f(0.0, -y);
    glEnd();
    
    glBegin(GL_LINES);
    glVertex2f(0.0, -y);
    glVertex2f(-x, 0.0);
    glEnd();
    
    glBegin(GL_LINES);
    glVertex2f(-x, 0.0);
    glVertex2f(0.0, y);
    glEnd();
    
    glBegin(GL_LINES);
    glVertex2f(0.0, y);
    glVertex2f(x, 0.0);
    glEnd();
}

void drawRhombus(float x, float y) {
    glColor3f(0.2, 0.6, 0.3);
    glBegin(GL_LINES);
    glVertex2f(x, y);
    glVertex2f(x, -y);
    glEnd();
    
    glBegin(GL_LINES);
    glVertex2f(x, -y);
    glVertex2f(-x, -y);
    glEnd();
    
    glBegin(GL_LINES);
    glVertex2f(-x, -y);
    glVertex2f(-x, y);
    glEnd();
    
    glBegin(GL_LINES);
    glVertex2f(-x, y);
    glVertex2f(x, y);
    glEnd();
}

void drawShape(float x, float y){
    int k = 1;
    while(x >= (0.0125)) {
        if(k % 2)
        {
            drawRhombus(x, y);
        }
        else
        {
            drawSquare(x, y);
            x = x/2;
            y = y/2;
        }
        
        k++;
    }
}

void display()
{
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    
    drawShape(x, y);
    
    glutSwapBuffers();
}

int main(int argc,char **argv)
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB|GLUT_DEPTH);
    glutInitWindowSize(600,600);
    glutCreateWindow("Animation of Squares");
    
    glClearColor(0.25, 0.25, 0.25, 0.3);
    
    glutDisplayFunc(display);
    glutIdleFunc(display);
    
    glutSpecialFunc(keyPressed);
    glutMainLoop();
    return(0);
}