1 #include "windows.h"  2 #include <gl\glut.h>  3   4 #define SunSize 0.4  5 #define EarthSize 0.06  6 #define MoonSize 0.016  7   8 GLfloat SpeedMultiplicator = 1.0;  9 GLfloat DaysPerYear = 50.0; //OK, ok... but it is soo slow with 360! 10 GLfloat year = 0.0; //degrees 11 GLfloat day = 0.0; 12 GLfloat moonAroundEarth = 0.0; 13 GLfloat moonItsSelf = 0.0; 14 GLfloat EarthOrbitRadius = 1.0; 15 GLfloat MoonOrbitRadius = 0.1; 16 GLfloat daySpeed = 5.0 * SpeedMultiplicator; 17 GLfloat yearSpeed = DaysPerYear / 360.0 * daySpeed * SpeedMultiplicator; 18 GLfloat moonAroundEarthSpeed = 10 * SpeedMultiplicator; 19 GLfloat moonItsSelfSpeed = 5 * SpeedMultiplicator; 20 void RenderScene(void) 21 { 22     glPushMatrix(); 23         gluLookAt(    0.0,0.0,-4.0, 24                     0.0,0.0,1.0, 25                     0.0,-3.0,0.0); 26         glColor3f(1.0,1.0,0.6); 27         glutWireSphere(SunSize,50,50); 28         glPushMatrix(); 29             glRotatef(year,0.0,1.0,0.0); 30             glTranslatef(EarthOrbitRadius,0.0,0.0); 31             glRotatef(-year,0.0,1.0,0.0); 32             glPushMatrix(); 33                 glRotatef(day,0.25,1.0,0.0); 34                 glColor3f(0.0,0.5,0.8); 35                 glutWireSphere(EarthSize,10,10);  //Draw earth 36                 //Draw earth rotation axis 37                 glBegin(GL_LINES); 38                     glVertex3f(-0.0625,-0.25,0.0); 39                     glVertex3f(0.0625,0.25,0.0); 40                 glEnd(); 41             glPopMatrix(); 42             glRotatef(moonAroundEarth,0.0,1.0,0.0); 43             glTranslatef(MoonOrbitRadius,0.0,0.0); 44             //The following 2 lines should be combined, but it is better to understand this way 45             glRotatef(-moonAroundEarth,0.0,1.0,0.0); 46             glRotatef(moonItsSelf,0.0,1.0,0.0); 47             glColor3f(0.8,0.8,0.75); 48             glutWireSphere(MoonSize,8,8); 49         glPopMatrix(); 50                  51     glPopMatrix(); 52 } 53  54 void Init(void) 55 { 56     glClearColor(0.0,0.0,0.0,0.0); 57     glClearDepth(10.0); 58     glMatrixMode(GL_MODELVIEW); 59     glLoadIdentity(); 60 } 61  62 void Display(void) 63 { 64     glClear(GL_COLOR_BUFFER_BIT); 65     RenderScene(); 66     glFlush(); 67     glutSwapBuffers(); 68 } 69  70 void Reshape(int x, int y) 71 { 72     if (y == 0) return; 73     glMatrixMode(GL_PROJECTION); 74     glLoadIdentity(); 75     gluPerspective(40.0,(GLdouble)x/(GLdouble)y,0.5,20.0); 76     glMatrixMode(GL_MODELVIEW); 77     glViewport(0,0,x,y); 78     Display(); 79 } 80 static long long times = 0; 81 void Idle(void) 82 { 83     times++; 84     if(times>1000000) 85         times =0; 86     if(times% 1000000== 0) 87     { 88         day += daySpeed; 89         year += yearSpeed; 90         moonItsSelf += moonItsSelfSpeed; 91         moonAroundEarth += moonAroundEarthSpeed; 92         Display(); 93     } 94 } 95  96  97 int main(int argc, char* argv[]) 98 { 99     glutInit(&argc, argv);100     glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);101     glutInitWindowSize(600,600);102     glutCreateWindow(argv[0]);103     Init();104     glutReshapeFunc(Reshape);105     glutDisplayFunc(Display);106     glutIdleFunc(Idle);107     glutMainLoop();108     return 0;109 }