//計算gluLookAt矩陣  
#pragma once
#include <windows.h>
#define GLUT_DISABLE_ATEXIT_HACK
#include <gl/glut.h>
#include <atlimage.h>
#include <math.h>
//不顯示控制檯視窗  
//#pragma comment( linker, "/subsystem:\"windows\" /entry:\"mainCRTStartup\"")  

float g_RotAngle = 0.5;

void TimerFunction(int value)
{
	g_RotAngle += 1.0;
	if (g_RotAngle>=360)
	{
		g_RotAngle = 0;
	}
	glutPostRedisplay();
	glutTimerFunc(10, TimerFunction, 1);
}
void display()
{
	//glMatrixMode( GL_MODELVIEW );
	//glLoadIdentity();
	glClear(GL_COLOR_BUFFER_BIT);
	glColor3f(1.0, 0.0, 0.0);
	//畫分割線，分成四個視見區
	glViewport(0, 0, 800, 600);
	glBegin(GL_LINES);
	glVertex2f(-1.0, 0);
	glVertex2f(1.0, 0);
	glVertex2f(0.0, -1.0);
	glVertex2f(0.0, 1.0);
	glEnd();
	//定義在左下角的區域
	glColor3f(0.0, 1.0, 0.0);
	glViewport(0, 0, 400, 300);
	glPushMatrix();
	glRotatef(g_RotAngle, 0.0, 1.0, 0.0);
	glBegin(GL_POLYGON);
	glVertex2f(-0.5, -0.5);
	glVertex2f(-0.5, 0.5);
	glVertex2f(0.5, 0.5);
	glVertex2f(0.5, -0.5);
	glEnd();
	glPopMatrix();

	//定義在右上角的區域
	glColor3f(0.0, 0.0, 1.0);
	glViewport(400, 300, 400, 300);//一定要注意，後面這兩個引數是高度和寬度，而不是座標
	glPushMatrix();
	glRotatef(-g_RotAngle, 0.0, 1.0, 0.0);
	glBegin(GL_POLYGON);
	glVertex2f(-0.5, -0.5);
	glVertex2f(-0.5, 0.5);
	glVertex2f(0.5, 0.5);
	glVertex2f(0.5, -0.5);
	glEnd();
	glPopMatrix();
	//定義在左上角的區域
	glColor3f(1.0, 0.0, 1.0);
	glViewport(0, 300, 400, 300);//一定要注意，後面這兩個引數是高度和寬度，而不是座標
	glPushMatrix();
	glRotatef(-2*g_RotAngle, 0.0, 1.0, 0.0);
	glBegin(GL_POLYGON);
	glVertex2f(-0.5, -0.5);
	glVertex2f(-0.5, 0.5);
	glVertex2f(0.5, 0.5);
	glVertex2f(0.5, -0.5);
	glEnd();
	glPopMatrix();
	//定義在右下角
	glColor3f(1.0, 1.0, 0.0);
	glViewport(400, 0, 400,300);//一定要注意，後面這兩個引數是高度和寬度，而不是座標
	glPushMatrix();
	glRotatef(-3*g_RotAngle, 0.0, 1.0, 0.0);
	glBegin(GL_POLYGON);
	glVertex2f(-0.5, -0.5);
	glVertex2f(-0.5, 0.5);
	glVertex2f(0.5, 0.5);
	glVertex2f(0.5, -0.5);
	glEnd();
	glPopMatrix();
	glFlush();
}
void init()
{
	glClearColor(0.0, 0.0, 0.0, 0.0);
	glColor3f(1.0, 1.0, 1.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	//定義剪裁面
	gluOrtho2D(-1.0, 1.0, -1.0, 1.0);
	//glViewport( 0, 0, 200, 200 ); //放在這裡不好使
}
int main(int argc, char ** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	glutInitWindowPosition(100, 100);
	glutInitWindowSize(800, 600);
	glutCreateWindow("OpenGL多視口程式設計");
	glutDisplayFunc(display);
	init();
	glutTimerFunc(1, TimerFunction, 1);
	glutMainLoop();
}