#include <gl/glut.h>

float fEarth = 2.0f; //地球繞太陽的旋轉角度

float fMoon = 24.0f; //月球繞地球的旋轉角度

void Init()

{

glEnable(GL_DEPTH_TEST); //啟用深度測試

glClearColor(0.0f, 0.0f, 0.0f, 0.8f); //背景為黑色

}

void Reshape(int w, int h)

{

if (0 == h)

h = 1;

glViewport(0, 0, w, h); //設定視區尺寸

glMatrixMode(GL_PROJECTION); //指定當前操作投影矩陣堆疊

glLoadIdentity(); //重置投影矩陣

//指定透視投影的觀察空間

gluPerspective(45.0f, (float)w / (float)h, 1.0f, 1000.0f);

glMatrixMode(GL_MODELVIEW);

glLoadIdentity();

}

void Display(void)

{

//清除顏色和深度緩衝區

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glMatrixMode(GL_MODELVIEW); //指定當前操作模型檢視矩陣堆疊

glLoadIdentity(); //重置模型檢視矩陣

glTranslatef(0.0f, 0.0f, -500.0f); //將圖形沿z軸負向移動

glColor3f(1.0f, 0.0f, 0.0f); //畫太陽

glutSolidSphere(50.0f, 20, 20);

glColor3f(0.0f, 0.0f, 1.0f);

glRotatef(23.27,0.0,0.0,1.0); //地球與太陽的黃赤交角

glRotatef(fEarth, 0.0f, 1.0f, 0.0f);

glTranslatef(200.0f, 0.0f, 0.0f);

glutSolidSphere(20.0f, 20, 20); //畫地球

glPopMatrix();

glPopMatrix();

glRotatef(6.0f, 1.0f, 1.0f, 1.0f);

glRotatef(fMoon, 0.0f, 1.0f, 0.0f);

glColor3f(1.0f, 1.0f, 0.0f);

glTranslatef(30.0f, 0.0f, 0.0f);

glutSolidSphere(5.0f, 20, 20); //畫月球

glLoadIdentity();

glFlush();

glutSwapBuffers();

}

void myIdle(void) //在空閒時呼叫，達到動畫效果

{

fEarth += 0.03f; //增加旋轉步長，產生動畫效果

if (fEarth > 360.0f)

fEarth = 2.0f;

fMoon += 0.24f;

if (fMoon > 360.0f)

fMoon = 24.0f;

Display();

}

int main(int argc, char *argv[])

{

glutInit(&argc, argv);

//視窗使用RGB顏色，雙快取和深度快取

glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);

glutInitWindowPosition(100,100);

glutInitWindowSize(600, 400);

glutCreateWindow("太陽系動畫");

glutReshapeFunc(Reshape);

glutDisplayFunc(Display);

glutIdleFunc(&myIdle);

Init();

glutMainLoop();

return 0;

}