#include <windows.h>
#include <gl/gl.h>
#include <gl/glaux.h>
#include <math.h>
#include <time.h>

#pragma comment(lib, "opengl32.lib")
#pragma comment(lib, "glu32.lib")
#pragma comment(lib, "glaux.lib")


float starData[8];//存储目标五角星数据的全局变量
//按序为xc, yc, r1, r2, angle, R, G, B


void init()
{
    glClearColor(0.0, 0.0, 0.0, 1.0);//黑色背景
}

/**
版本号：2.0
功能：计算五角星的10个顶点坐标
参数：
    points      存放10个顶点坐标的数组
    xc, yc      中心坐标    
    r1          五角星外面5个顶点所在圆的半径
    r2          里面5个顶点所在圆的半径，r2<r1
    angle       弧度表示的倾斜度，0为标准，数值增大表示向逆时针方向倾斜
**/
void getStarPoints(float points[10][2], float xc, float yc, float r1, float r2, float angle)
{
    const float PI = 3.14;
    
    int i, r;

    angle = angle + 0.1 * PI;

    for (i=0; i<=9; i++)
    {
        r = (i%2==0)?r1:r2;
        points[i][0] = xc + (float)r*cos(angle+i*0.2*PI);
        points[i][1] = yc + (float)r*sin(angle+i*0.2*PI);
    }

}

void render()
{
    int con;
    float points[10][2];

    getStarPoints(points, starData[0], starData[1], starData[2], starData[3], starData[4]);

    glColor3f(starData[5], starData[6], starData[7]);
    
    for (con=0; con<=9; con++)
    {
        glBegin(GL_LINES);
        glVertex2f(points[con][0], points[con][1]);
        glVertex2f(points[(con+1)%10][0], points[(con+1)%10][1]);
        glEnd();
    }
}

void CALLBACK draw()
{
    glClear(GL_COLOR_BUFFER_BIT);
    render();
    glFinish();
}

void CALLBACK change()
{
    int i;

    srand(time(NULL));
    
    i = rand()%300 + 100;   //xc从100到400
    starData[0] = (float)i;
    
    i = rand()%300 + 100;   //yc从100到400
    starData[1] = (float)i;
    
    i = rand()%40 + 60;     //r1从60到100
    starData[2] = (float)i;

    i = rand()%30 + 20;     //r2从20到50
    starData[3] = (float)i;
    
    i = rand()%6;           //偏转角度从0到6
    starData[4] = i/1.0f;

    i = rand()%200;         //RGB中红色的比例从0到1
    starData[5] = i/200.0f;

    i = rand()%200;         //RGB中绿色的比例从0到1
    starData[6] = i/200.0f;

    i = rand()%200;         //RGB中蓝色的比例从0到1
    starData[7] = i/200.0f;
    
    draw();
}

void main()
{
    auxInitDisplayMode(AUX_SINGLE|AUX_RGBA);
    auxInitPosition(200, 100, 500, 500);
    auxInitWindow("CGOpenGL");

    init();
    
    auxIdleFunc(change);
    auxMainLoop(draw);
    
}