This C++ program simulates the rotation and orbits of the sun, earth, and moon in our solar system. It defines variables to track the positions, radii, and rotation rates of each celestial body. The drawSolarSystem() function renders the sun, earth, and moon by applying translations and rotations to position them correctly. The display, reshape, and idle functions continuously update the rotation values and redraw the scene.

1. #include "windows.h"
#include <glglut.h>
#define sunRaduis 0.4
#define earthRaduis 0.08
#define moonRaduis 0.018
GLfloat rotationSpeed = 0.07;
GLfloat daysInYear = 365;
GLfloat year = 0.0; //in degrees
GLfloat day = 0.0;
GLfloat moonAroundEarth = 0.0;
GLfloat moonItsSelf = 0.0;
GLfloat earthOrbitRadius = 1.2;
GLfloat moonOrbitRadius = 0.2;
GLfloat moonAroundEarthRate = 1 * rotationSpeed;
GLfloat moonRotationItselfRate = 1.0 * rotationSpeed;
GLfloat dayRate = 5.0 * rotationSpeed;
GLfloat yearRate = daysInYear / 360.0 * dayRate * rotationSpeed;
void drawSolarSystem()
{
glPushMatrix();
gluLookAt(0.0,0.0,-3.0,0.0,0.0,1.0,0.0,-3.0,0.0);
//Drawing the sun.
glColor3f(1,0,0);
glutSolidSphere(sunRaduis,40,40);
glPushMatrix();
glRotatef(year,0.0,0,1.0); //rotation for earth around
y-axis
glTranslatef(earthOrbitRadius,0.0,1.0); //
translation for earth around y-axis
glRotatef(-year,0.0,0,1.0); //rotation for earth around
y-axis
//EARTH
glPushMatrix();
//color earth
glColor3f(0.0,0.0,1);
//Drawing earth
glutSolidSphere(earthRaduis,10,10);
glPopMatrix();
// rotation for moon.
glRotatef(moonAroundEarth,0.0,0.0,1.0);
// translation for moon.
glTranslatef(moonOrbitRadius,0.2,0.2); //we took along x-axis and y-axis
// around earth rotation.
glRotatef(-moonAroundEarth,0.0,0.0,1.0);
glColor3f(1,1,1);
// drawing moon
glutSolidSphere(moonRaduis,20,20);
glPopMatrix();
glPopMatrix();
}
void Initialization()
{
glClearColor(0.0,0.0,0.0,0.0);
glClearDepth(10.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

2. }
void displayFunc()
{
glClear(GL_COLOR_BUFFER_BIT);
//now going to drawSolarSystem() function
drawSolarSystem();
glFlush();
glutSwapBuffers();
}
void reshapeFunc(int x, int y)
{
if (y == 0 || x==0) return;
glLoadIdentity();
gluPerspective(45,(GLdouble)x/(GLdouble)y,0.5,200.0);
glMatrixMode(GL_MODELVIEW);
glViewport(0,0,x,y);
//now going to displayFunc() function
displayFunc();
}
void idleFunc(void)
{
// idle event call back,here we increase the values and redisply .
day = day + dayRate;
year= year + yearRate;
moonItsSelf = moonItsSelf + moonRotationItselfRate;
moonAroundEarth = moonAroundEarth + moonAroundEarthRate;
//now going to displayFunc() function
displayFunc();
}
int main(int argc, char* argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(800,800);
glutCreateWindow("Sun,Earth,Moon = ROTATION ");
Initialization();
glutDisplayFunc(displayFunc);
glutReshapeFunc(reshapeFunc);
glutIdleFunc(idleFunc);
glutMainLoop();
return 0;
}