第四个程序opengl简单的动画效果。

先上代码，稍后再解释；

// lesson6.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include 
#include 
#include 

static int day = 200;

double CalFrequency()
{
	static int count;
	static double save;
	static clock_t last, current;
	double timegap;

	++count;
	if( count <= 50 )
		return save;
	count = 0;
	last = current;
	current = clock();
	timegap = (current - last ) / (double)CLK_TCK;
	save = 50.0 / timegap;

	return save;
	
}

void myDisplay(void)
{
	double FPS = CalFrequency();
	printf("FPF = %f\n", FPS);

	glEnable(GL_DEPTH_TEST);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(75, 1, 1, 400000000);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt(0, -200000000, 200000000, 0, 0, 0, 0, 0, 1);

    // 绘制红色的“太阳”
    glColor3f(1.0f, 0.0f, 0.0f);
    glutSolidSphere(69600000, 20, 20);

    // 绘制蓝色的“地球”
    glColor3f(0.0f, 0.0f, 1.0f);
    glRotatef(day/360.0*360.0, 0.0f, 0.0f, -1.0f);
    glTranslatef(150000000, 0.0f, 0.0f);
    glutSolidSphere(15945000, 20, 20);

    // 绘制黄色的“月亮”
    glColor3f(1.0f, 1.0f, 0.0f);
    glRotatef(day/30.0*360.0 - day/360.0*360.0, 0.0f, 0.0f, -1.0f);
    glTranslatef(38000000, 0.0f, 0.0f);
    glutSolidSphere(4345000, 20, 20);

    glFlush();

	glutSwapBuffers();
}

void myIdle(void)
{
	++day;
	if( day >= 360 )
		day = 0;
	myDisplay();

}

int main(int argc, char* argv[])
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE); // 修改了参数为GLUT_DOUBLE
	glutInitWindowPosition(100, 100);
	glutInitWindowSize(400, 400);
	glutCreateWindow("太阳，地球和月亮");
	glutDisplayFunc(&myDisplay);
	glutIdleFunc(&myIdle);        // 表示在CPU空闲的时间调用某一函数
	glutMainLoop();
	
	return 0;
}

运行结果：