openGL 大作业之n星变换

#include "stdafx.h"
#include<stdio.h>
#define GLUT_DISABLE_ATEXIT_HACK //不写这句话总运行出错，我也不知道为啥。。。
#include<gl/GLUT.h>
#include<math.h>
int change = 10;
static GLfloat spin = 0.0;//static:静态全局变量，只要程序运行，内存中一直存在，文件内可见，文件外不可见

void init(void)
{
    glClearColor(0.0, 0.0, 0.0, 0.0);//将清空颜色设置为黑
    
}
int z = -1;
void fillOption(GLint selectedOption)
{
     z = -1;
    switch (selectedOption) {
    case 1:change-=2;   break; 
    case 2:z=-z;  break; 
    case 3:z =0;  break;
    }
    glutPostRedisplay();
}
void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);//清除颜色缓存
    glPushMatrix();//将当前矩阵压栈（保存现场）
    glRotatef(spin, 0.0, 0.0,z);//旋转方向，遵循右手原则
    glColor3f(1.0, 1.0, 1.0);
    glEnable(GL_LINE_SMOOTH);//让线条更平滑
    GLint x = 100;
    GLdouble a = 1.256637, c = 1;
    while (x--)
    {
        glShadeModel(GL_SMOOTH);//渐变色
        glBegin(GL_LINE_STRIP);
        
        glVertex2f(50 * cos(a + c), 50 * sin(a + c));
        glColor3f(1.0, 0.0, 0.0);
        glVertex2f(50 * cos(3 * a + c), 50 * sin(3 * a + c));
        glColor3f(0.0, 1.0, 0.0);
        glVertex2f(50 * cos(5 * a + c), 50 * sin(5 * a + c));
        glColor3f(0.0, 0.0, 1.0);
        glVertex2f(50 * cos(2 * a + c), 50 * sin(2 * a + c));
        glColor3f(0.0, 1.0, 1.0);
        glVertex2f(50 * cos(4 * a + c), 50 * sin(4 * a + c));
        glColor3f(1.0, 1.0, 1.0);
        glVertex2f(50 * cos(a + c), 50 * sin(a + c));
        glEnd();
        c+=0.0314159365*change;
        
    }
    glColor3f(1.0, 0.0, 0.0);
    glBegin(GL_LINE_STRIP);
    
    glEnd();
    glPopMatrix();
    glutSwapBuffers();//双缓存技术的函数，作用为交换两个缓冲区的指针
}
void spinDisplay(void)
{
    spin = spin + 0.04;
    if (spin > 360.0)
    {
        spin = spin - 360.0;
    }
    glutPostRedisplay();//glutPostRedisplay 标记当前窗口需要重新绘制。通过glutMainLoop下一次循环时，窗口显示将被回调以重新显示窗口的正常面板
}
void reshape(int w, int h)
{
    glViewport(0, 0, (GLsizei)w, (GLsizei)h);//函数作用：用一个视景体截取图像
    glMatrixMode(GL_PROJECTION);//mode 指定哪一个矩阵堆栈是下一个矩阵操作的目标,参数表示接下来要进行投影相关的操作
    glLoadIdentity();//设置当前变化矩阵为单位矩阵；单位矩阵就是对角线上都是1，其余元素皆为0的矩阵。然后复位
    glOrtho(-50.0, 50.0, -50.0, 50.0, -1.0, 1.0);
    glMatrixMode(GL_MODELVIEW);//进行视景相关的操作
    glLoadIdentity();
}
void mouse(int button, int state, int x, int y)
{
    switch (button)
    {
    case GLUT_LEFT_BUTTON:
        if (state == GLUT_DOWN)
            glutIdleFunc(spinDisplay);//glutIdleFunc函数如果启用，这个idle function会被不断调用，直到有窗口事件发生
        break;
    case GLUT_RIGHT_BUTTON:
        if (state == GLUT_DOWN)
            glutIdleFunc(NULL);
        break;
    default:
        break;
    }
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(680, 680);
    glutInitWindowPosition(400, 0);
    glutCreateWindow("big homework");
    init();
    glutDisplayFunc(display);//每次重绘场景时调用
    glutCreateMenu(fillOption);  
    glutAddMenuEntry("amount", 1);
    glutAddMenuEntry("reverse", 2);
    glutAddMenuEntry("narrow", 3);
    glutAttachMenu(GLUT_RIGHT_BUTTON);
    glutReshapeFunc(reshape);//每次窗口改变时调用
    glutMouseFunc(mouse);//每次使用鼠标时调用
    glutMainLoop();
    return 0;
}