OpenGL 2D 旋转问题

Question

在下面的程序中，我试图画一个简单的房子。坐标在 house 数组中定义。我需要旋转房子并显示旋转后的房子和原始房子。 但为什么旋转后的房子没有显示出来呢？

    //Program to create a house like figure and rotate ir about a given fixed point using OpenGL functions.
#include <glut.h>
#include <stdio.h>

float house [11][2] = {{100,200},{200,250},{300,200},{100,200},{100,100},{175,100},{175,150},{225,150},{225,100},{300,100},{300,200}};

void init()
{
    glClearColor(1,1,1,0);
    glMatrixMode(GL_PROJECTION);
    gluOrtho2D(0,800,0,800);
    glMatrixMode(GL_MODELVIEW);
}

void display()
{
    glClear(GL_COLOR_BUFFER_BIT);

    //NORMAL HOUSE
    glColor3f(1,0,0);
    glBegin(GL_LINE_LOOP);

    for(int i=0;i<11;i++)
        glVertex2fv(house[i]);
    glEnd();
    glFlush();


    //ROTATED HOUSE
    glPushMatrix();
    glRotatef(60,0,1,0);
    glColor3f(1,1,0);
    glBegin(GL_LINE_LOOP);

    for(int i=0;i<11;i++)
        glVertex2fv(house[i]);
    glEnd();
    glFlush();
    glPopMatrix();
}

void main(int argc,char** argv)
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(800,800);
    glutInitWindowPosition(100,100);
    glutCreateWindow("House rotation");
    init();
    glutDisplayFunc(display);
    glutMainLoop();
}

Answer 1

尝试在 Z 轴而不是 Y 轴上旋转：

//Program to create a house like figure and rotate ir about a given fixed point using OpenGL functions.
#include <GL/glut.h>

float house [11][2] = {{100,200},{200,250},{300,200},{100,200},{100,100},{175,100},{175,150},{225,150},{225,100},{300,100},{300,200}};

void display()
{
    glClearColor(1,1,1,0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0,800,0,800);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    //NORMAL HOUSE
    glColor3f(1,0,0);
    glBegin(GL_LINE_LOOP);
    for(int i=0;i<11;i++)
        glVertex2fv(house[i]);
    glEnd();


    //ROTATED HOUSE
    glPushMatrix();
    glTranslatef(100,100,0);
    glRotatef(60,0,0,1);
    glTranslatef(-100,-100,0);
    glColor3f(1,1,0);
    glBegin(GL_LINE_LOOP);
    for(int i=0;i<11;i++)
        glVertex2fv(house[i]);
    glEnd();
    glPopMatrix();
}

void main(int argc,char** argv)
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(800,800);
    glutInitWindowPosition(100,100);
    glutCreateWindow("House rotation");
    glutDisplayFunc(display);
    glutMainLoop();
}

编辑：这应该绕底角旋转。