OpenGL program for simple Animation (Revolution) in C

// C Program to illustrate 
// OpenGL animation for revolution

#include<stdio.h>
#include<GL/glut.h>
#include<math.h>

// global declaration
int x, y;
float i, j;

// Initialization function
void myInit (void)
{
    // Reset background color with black (since all three argument is 0.0)
    glClearColor(0.0, 0.0, 0.0, 1.0);
    
    // Set picture color to green (in RGB model)
    // as only argument corresponding to G (Green) is 1.0 and rest are 0.0
    glColor3f(0.0, 1.0, 0.0);
    
    // Set width of point to one unit
    glPointSize(1.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    
    // Set window size in X- and Y- direction
    gluOrtho2D(-780, 780, -420, 420);
}

// Function to display animation
void display (void)
{
    // Outer loop to make figure moving
    // loop variable j iterated up to 10000,
    // indicating that figure will be in motion for large amount of time
    // around 10000/6.29 = 1590 time it will revolve
    // j is incremented by small value to make motion smoother
    for (j = 0; j < 10000; j += 0.01)
    {
        glClear(GL_COLOR_BUFFER_BIT);
        glBegin(GL_POINTS);
        
        // Iterate i up to 2*pi, i.e., 360 degree
        // plot point with slight increment in angle,
        // so, it will look like a continuous figure

        // Loop is to draw outer circle
        for (i = 0;i < 6.29;i += 0.001)
        {
            x = 200 * cos(i);
            y = 200 * sin(i);
            glVertex2i(x, y);
            
            // For every loop, 2nd glVertex function is
            // to make smaller figure in motion
            glVertex2i(x / 2 - 600 * cos(j), y / 2 - 100 * sin(j));
        }
        
        // 7 loops to draw parallel latitude
        for (i = 1.17; i < 1.97; i += 0.001)
        {
            x = 400 * cos(i);
            y = -150 + 300 * sin(i);
            glVertex2i(x, y);
            glVertex2i(x / 2 - 600 * cos(j), y / 2 - 100 * sin(j));
        }
        
        for (i = 1.07; i < 2.07; i += 0.001)
        {
            x = 400 * cos(i);
            y = -200 + 300 * sin(i);
            glVertex2i(x, y);
            glVertex2i(x / 2 - 600 * cos(j), y / 2 - 100 * sin(j));
        }
        
        for (i = 1.05; i < 2.09; i += 0.001)
        {
            x = 400 * cos(i);
            y = -250 + 300 * sin(i);
            glVertex2i(x, y);
            glVertex2i(x / 2 - 600 * cos(j), y / 2 - 100 * sin(j));
        }
        
        for (i = 1.06; i < 2.08; i += 0.001)
        {
            x = 400 * cos(i);
            y = -300 + 300 * sin(i);
            glVertex2i(x, y);
            glVertex2i(x / 2 - 600 * cos(j), y / 2 - 100 * sin(j));
        }
        
        for (i = 1.10; i < 2.04; i += 0.001)
        {
            x = 400 * cos(i);
            y = -350 + 300 * sin(i);
            glVertex2i(x, y);
            glVertex2i(x / 2 - 600 * cos(j), y / 2 - 100 * sin(j));
        }
        
        for (i = 1.16; i < 1.98; i += 0.001)
        {
            x = 400 * cos(i);
            y = -400 + 300 * sin(i);
            glVertex2i(x, y);
            glVertex2i(x / 2 - 600 * cos(j), y / 2 - 100 * sin(j));
        }
        
        for (i = 1.27; i < 1.87; i += 0.001)
        {
            x = 400 * cos(i);
            y = -450 + 300 * sin(i);
            glVertex2i(x, y);
            glVertex2i(x / 2 - 600 * cos(j), y / 2 - 100 * sin(j));
        }
        
        // Loop is to draw vertical line
        for (i = 200; i >=- 200; i--)
        {
            glVertex2i(0, i);
            glVertex2i(-600 * cos(j), i / 2 - 100 * sin(j));
        }
        
        // 3 loops to draw vertical ellipse (similar to longitude)
        for (i = 0;i < 6.29; i += 0.001)
        {
            x = 70 * cos(i);
            y = 200 * sin(i);
            glVertex2i(x, y);
            glVertex2i(x / 2 - 600 * cos(j), y / 2 - 100 * sin(j));
        }
        
        for (i = 0; i < 6.29; i += 0.001)
        {
            x = 120 * cos(i);
            y = 200 * sin(i);
            glVertex2i(x, y);
            glVertex2i(x / 2 - 600 * cos(j), y / 2 - 100 * sin(j));
        }
        
        for (i = 0; i < 6.29; i += 0.001)
        {
            x = 160 * cos(i);
            y = 200 * sin(i);
            glVertex2i(x, y);
            glVertex2i(x / 2 - 600 * cos(j), y / 2 - 100 * sin(j));
        }
        
        // Loop to make orbit of revolution
        for (i = 0; i < 6.29; i += 0.001)
        {
            x = 600 * cos(i);
            y = 100 * sin(i);
            glVertex2i(x, y);
        }
        glEnd();
        glFlush();
    }
}

// Driver Program
int main (int argc, char** argv)
{
    glutInit(&argc, argv);
    
    // Display mode which is of RGB (Red Green Blue) type
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    
    // Declares window size
    glutInitWindowSize(1360, 768);
    
    // Declares window position which is (0, 0)
    // means lower left corner will indicate position (0, 0)
    glutInitWindowPosition(0, 0);

    // Name to window
    glutCreateWindow("Revolution");

    // Call to myInit()
    myInit();
    glutDisplayFunc(display);
    glutMainLoop();
}