【OpenGL】画立方体

编写一个程序，该程序运行时可以用鼠标的一个按键调整立方体的方向，用另一个按键平移立方体，用第三个按键缩放立方体。

这是题目，我的程序不一定完全按照这个来。初学OpenGL，对那一堆坐标系表示十分混乱，慢慢看吧，有点头绪了。

（一）

 #include <gl/glut.h>
 #include <math.h>
 #define GL_PI 3.1415f

 GLfloat xRot = -35.0f;
 GLfloat yRot = 15.0f;
 GLfloat xMov = 0.0f;
 GLfloat winW = 0.0f;
 GLfloat winH = 0.0f;
 GLfloat zoom = 1.0f;

 void RenderScene(void)
 {
     glClear(GL_COLOR_BUFFER_BIT);

     glPushMatrix();
     glLoadIdentity();
     glRotatef(xRot, 1.0f, 0.0f, 0.0f);
     glRotatef(yRot, 0.0f, 1.0f, 0.0f);

     // 底面
     glBegin(GL_LINE_LOOP);
     glVertex3f(0.0f+xMov, 0.0f, 0.0f);
     glVertex3f(1.0f+xMov, 0.0f, 0.0f);
     glVertex3f(1.0f+xMov, 0.0f, 1.0f);
     glVertex3f(0.0f+xMov, 0.0f, 1.0f);
     glEnd();

     // 顶面
     glBegin(GL_LINE_LOOP);
     glVertex3f(0.0f+xMov, 1.0f, 1.0f);
     glVertex3f(0.0f+xMov, 1.0f, 0.0f);
     glVertex3f(1.0f+xMov, 1.0f, 0.0f);
     glVertex3f(1.0f+xMov, 1.0f, 1.0f);
     glEnd();

     // 背面
     glBegin(GL_LINE_LOOP);
     glVertex3f(0.0f+xMov, 0.0f, 0.0f);
     glVertex3f(1.0f+xMov, 0.0f, 0.0f);
     glVertex3f(1.0f+xMov, 1.0f, 0.0f);
     glVertex3f(0.0f+xMov, 1.0f, 0.0f);
     glEnd();

     // 前面
     glBegin(GL_LINE_LOOP);
     glVertex3f(1.0f+xMov, 0.0f, 1.0f);
     glVertex3f(0.0f+xMov, 0.0f, 1.0f);
     glVertex3f(0.0f+xMov, 1.0f, 1.0f);
     glVertex3f(1.0f+xMov, 1.0f, 1.0f);
     glEnd();

     // 右面
     glBegin(GL_LINE_LOOP);
     glVertex3f(1.0f+xMov, 0.0f, 0.0f);
     glVertex3f(1.0f+xMov, 0.0f, 1.0f);
     glVertex3f(1.0f+xMov, 1.0f, 1.0f);
     glVertex3f(1.0f+xMov, 1.0f, 0.0f);
     glEnd();

     // 左面
     glBegin(GL_LINE_LOOP);
     glVertex3f(0.0f+xMov, 0.0f, 0.0f);
     glVertex3f(0.0f+xMov, 0.0f, 1.0f);
     glVertex3f(0.0f+xMov, 1.0f, 1.0f);
     glVertex3f(0.0f+xMov, 1.0f, 0.0f);
     glEnd();

     glPopMatrix();
     glFlush();
 }
 void OnReshape(int w, int h)
 {
     GLfloat aspectRatio = (GLfloat)w/(GLfloat)h;
     winW = w;
     winH = h;

     glViewport(,,w,h);
     glMatrixMode(GL_PROJECTION);
     glLoadIdentity();
     if (w <= h)
     {
         glOrtho(-3.0f*zoom, 3.0f*zoom, -3.0f*zoom/aspectRatio, 3.0f*zoom/aspectRatio, -10.0f*zoom, 10.0f*zoom);
     }
     else{
         glOrtho(-3.0f*zoom*aspectRatio, 3.0f*zoom*aspectRatio, -3.0f*zoom, 3.0f*zoom, -10.0f*zoom, 10.0f*zoom);
     }
     glMatrixMode(GL_MODELVIEW);
     glLoadIdentity();
 }
 void OnMouse(int button, int state, int x, int y)
 {
     if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
     {
         xRot += ;
         yRot += ;
         glutPostRedisplay();
     }
     else if (button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN)
     {
         xMov -= 0.1;
         glutPostRedisplay();
     }
     else if (button == GLUT_MIDDLE_BUTTON && state == GLUT_DOWN)
     {
         zoom += 0.1;
         OnReshape(winW,winH);
         glutPostRedisplay();
     }
 }
 void OnKeyUpDown(int key, int x, int y)
 {
     if (key == GLUT_KEY_UP){
         zoom -= 0.1;
     }
     else if (key == GLUT_KEY_DOWN){
         zoom += 0.1;
     }
     OnReshape(winW,winH);
     glutPostRedisplay();
 }

 void SetupRC()
 {
     glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
     glColor3f(0.0f, 1.0f, 0.0f);
 }

 void main(int argc, char **argv)
 {
     glutInit(&argc,argv);
     glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
     glutCreateWindow("Cube");
     glutDisplayFunc(RenderScene);
     glutReshapeFunc(OnReshape);
     glutMouseFunc(OnMouse);
     glutSpecialFunc(OnKeyUpDown);

     SetupRC();

     glutMainLoop();
 }

这个程序略长，显得有点笨。手工实现了平移和放大缩小的功能，值得记录一下。

（二）

 #include <windows.h>
 #include<gl/glut.h>
 #include <math.h>
 #include<stdio.h>

 GLfloat angle=0.0f;
 GLfloat translate_x=0.0f;
 GLfloat zoom=1.0f;

 void myDisplay()
 {
     glClear (GL_COLOR_BUFFER_BIT);
     glColor3f (1.0f, 1.0f, 1.0f);
     glPushMatrix();
     {
         glMatrixMode(GL_MODELVIEW);        //切换到模型视图矩阵
         glLoadIdentity();
         glRotatef(angle,1.0f,0.0f,0.0f);
         glRotatef(angle, 0.0f, 1.0f, 0.0f);
         glTranslatef(translate_x,0.0f,0.0f);
         glScalef (zoom, zoom, zoom);
         glutWireCube(1.5); //画立方体
     }
     glPopMatrix();
     glFlush();
 }

 void reshape(int w,int h)
 {
     glViewport (, , (GLsizei) w, (GLsizei) h);  //调整视口位置和大小
     glMatrixMode (GL_PROJECTION);//切换到投影矩阵
     glLoadIdentity();//加载单位阵至投影矩阵
     if (w <= h){
         glOrtho(-3.0f, 3.0f, -3.0f/(w/h), 3.0f/(w/h), -3.0f, 3.0f);
     }
     else{
         glOrtho(-3.0f*w/h, 3.0f*w/h, -3.0f, 3.0f, -3.0f, 3.0f);
     }

     glMatrixMode (GL_MODELVIEW);
     glLoadIdentity();
 }

 void OnMouse(int button, int state, int x, int y)
 {
     //鼠标左键
     if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
     {
         angle += 10.0f;
         glutPostRedisplay();
     }
     //鼠标右键
     else if (button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN)
     {
         translate_x+=0.1f;
         glutPostRedisplay();
     }
     //鼠标滚轮
     else if (state == GLUT_UP && button == GLUT_WHEEL_DOWN)
     {
         if(zoom>)
             zoom-=0.1f;
         glutPostRedisplay();
     }
     else if(state == GLUT_UP && button == GLUT_WHEEL_UP)
     {
         zoom+=0.1f;
         glutPostRedisplay();
     }
 }

 int main(int argc, char** argv)
 {
     glutInit(&argc, argv);
     glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
     glutInitWindowPosition(,);
     glutInitWindowSize(,);
     glutCreateWindow("cube");

     glutDisplayFunc(myDisplay);
     glutReshapeFunc(reshape);
     glutMouseFunc( OnMouse );
     glutMainLoop();
     return ;
 }

采用了OpenGL的一些库函数实现，投影还是采用平行投影，表示对透视投影函数gluPerspective以及视点变化函数gluLookAt不是很清楚。

（三）

 #include <windows.h>
 #include<gl/glut.h>
 #include <math.h>
 #include<stdio.h>

 GLfloat angle=0.0f;
 GLfloat translate_x=0.0f;
 GLfloat zoom=1.0f;

 void myDisplay()
 {
     glClear (GL_COLOR_BUFFER_BIT);
     glColor3f (1.0f, 1.0f, 1.0f);
     glPushMatrix();

     glMatrixMode(GL_MODELVIEW);        //切换到模型视图矩阵
     glLoadIdentity();
     gluLookAt (0.0f, 0.0f, 5.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f); //设置相机参数
     glRotatef(angle, 0.0f, 1.0f, 0.0f);
     glTranslatef(translate_x,0.0f,0.0f);
     glScalef (zoom, zoom, zoom);
     glutWireCube(0.5); //画立方体

     glPopMatrix();
     glFlush();
 }

 void reshape(int w,int h)
 {
     glViewport (, , (GLsizei) w, (GLsizei) h);  //调整视口位置和大小
     glMatrixMode (GL_PROJECTION);//切换到投影矩阵
     glLoadIdentity();//加载单位阵至投影矩阵
     gluPerspective(,w/h,,);
     glMatrixMode (GL_MODELVIEW);
     glLoadIdentity();
 }

 void OnMouse(int button, int state, int x, int y)
 {
     //鼠标左键
     if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
     {
         angle += 10.0f;
         glutPostRedisplay();
     }
     //鼠标右键
     else if (button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN)
     {
         //xMov -= 0.1;
         translate_x+=0.1f;
         glutPostRedisplay();
     }
     //鼠标滚轮
     else if (state == GLUT_UP && button == GLUT_WHEEL_DOWN)
     {
         if(zoom>)
             zoom-=0.1f;
         glutPostRedisplay();
     }
     else if(state == GLUT_UP && button == GLUT_WHEEL_UP)
     {
         zoom+=0.1f;
         glutPostRedisplay();
     }
 }

 int main(int argc, char** argv)
 {
     glutInit(&argc, argv);
     glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
     glutInitWindowPosition(,);
     glutInitWindowSize(,);
     glutCreateWindow("cube");

     glutDisplayFunc(myDisplay);
     glutReshapeFunc(reshape);
     glutMouseFunc( OnMouse );
     glutMainLoop();
     return ;
 }

用的是透视投影。我的理解是gluPerspective()和gluLookAt()要配合使用，二者中的相机位置要一致。