c++ - OpenGL _ Front 对象被 Back 对象覆盖。所以看不到-6ren

c++ - OpenGL _ Front 对象被 Back 对象覆盖。所以看不到

转载作者：塔克拉玛干更新时间：2023-11-03 01:54:57

问题是，' table 上的物体被 table 板覆盖，所以看不到它。'

(我使用的是 openGL 3.7 beta。我安装的文件是:http://ihoo1836.dothome.co.kr/opengl_vs2010+glutdlls37beta.zip)

所有代码如下。

#include<glut.h>
#include<stdio.h>
#include<stdlib.h>
#include<time.h>

float TableX = 5.0; //Table's X size
float TableY = 8.0; //Table's Y size
float TableHeight = 2.0;//Table's Height

int width=400, height=400;  //Window Size

int ViewX = width/2;        //for Change Viewpoint by Mouse position 
int ViewY = height/2;
int ViewZ = 9;

GLUquadricObj* cyl;

void InitLight( ){
    glEnable(GL_DEPTH_TEST);    //for opaque
    glEnable(GL_NORMALIZE);     //normalize
    glEnable(GL_SMOOTH);        //for smooth color
    glEnable(GL_LIGHTING);  //light setting
    glDepthMask(GL_TRUE);

    GLfloat ambientLight[] = {0.3f, 0.3f, 0.3f, 1.0f};
    GLfloat diffuseLight[] = {0.7f, 0.7f, 0.7f, 1.0f};
    GLfloat specular[] = {1.0f, 1.0f, 1.0f, 1.0f};
    GLfloat specref[] = {1.0f, 1.0f, 1.0f, 1.0f};
    GLfloat position[]={400.0, 300.0, -700.0, 1.0};

    glLightfv(GL_LIGHT0, GL_AMBIENT, ambientLight);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuseLight);
    glLightfv(GL_LIGHT0, GL_SPECULAR, specular);
    glLightfv(GL_LIGHT0, GL_POSITION, position);

    glEnable(GL_LIGHT0);
    glEnable(GL_COLOR_MATERIAL);

    glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
    glMateriali(GL_FRONT, GL_SHININESS, 128);
}

//Get Mouse Position to Change ViewPoint
void MyMouseMove(int button, int state, GLint X, GLint Y)
{
    //Get Mouse Position X, Y
    ViewX = X;
    ViewY = Y;

    glutPostRedisplay();
}

//Get Mouse Position to Change ViewPoint
void MyMotion(GLint X, GLint Y)
{
    //Get Mouse Position X, Y
    ViewX = X;
    ViewY = Y;

    glutPostRedisplay();
}


//Draw Table
void DrawTable(){
    glPushMatrix();
    glTranslatef(0.0,0.0,1.0);
    glColor3f(0.5, 0.25, 0.0);
    cyl = gluNewQuadric();
    glRotatef(-90,1.0,0.0,0.0);
    gluCylinder(cyl, 0.2, 0.2, TableHeight, 10, 20); //Leg of Table 1
        glPushMatrix();
        cyl = gluNewQuadric();
        glTranslatef(TableX,0.0,0.0);
        gluCylinder(cyl, 0.2, 0.2, TableHeight, 10, 20); //Leg of Table 2
            glPushMatrix();
            cyl = gluNewQuadric();
            glTranslatef(0.0, TableY, 0.0);
            gluCylinder(cyl, 0.2, 0.2, TableHeight, 10, 20); //Leg of Table 3
                glPushMatrix();
                cyl = gluNewQuadric();
                glTranslatef(-TableX,0.0,0.0);
                gluCylinder(cyl, 0.2, 0.2, TableHeight, 10, 20); //Leg of Table 4
                    glPushMatrix();
                    glTranslatef(TableX/2.0, -TableY/2, TableHeight);
                    glScalef(TableX+0.5, TableY+0.5, 0.5);
                    glutSolidCube(1);                           //Board of Table
                    glPopMatrix();

                    glPushMatrix();                         //triangular1 (Beside of Net)
                    glTranslatef(0, -TableY/2, TableHeight);
                    glBegin(GL_TRIANGLES);
                        glVertex3f(TableY/16.0, 0, TableY/8.0);//1
                        glVertex3f(0, TableY/8.0, 0);
                        glVertex3f(0, -TableY/8.0, 0);
                        glVertex3f(TableY/16.0, 0, TableY/8.0);//2
                        glVertex3f(0, -TableY/8.0, 0);
                        glVertex3f(TableY/16.0, -TableY/8.0, 0);
                        glVertex3f(TableY/16.0, 0, TableY/8.0);//3
                        glVertex3f(TableY/16.0, -TableY/8.0, 0);
                        glVertex3f(TableY/16.0, TableY/8.0, 0);
                        glVertex3f(TableY/16.0, 0, TableY/8.0);//4
                        glVertex3f(TableY/16.0, TableY/8.0, 0);
                        glVertex3f(0, TableY/8.0, 0);
                    glEnd();
                        glPushMatrix();                     //triangular2 (Beside of Net)
                        glTranslatef(TableX - TableY/8.0, 0 , 0);
                        glBegin(GL_TRIANGLES);
                            glColor3f(1.0, 0.0, 0.0);
                            glVertex3f(TableY/16.0, 0, TableY/8.0);//1
                            glColor3f(0.0, 1.0, 0.0);
                            glVertex3f(TableY/16.0, TableY/8.0, 0);                         
                            glColor3f(0.0, 0.0, 1.0);
                            glVertex3f(TableY/16.0, -TableY/8.0, 0);
                            glColor3f(1.0, 0.0, 0.0);
                            glVertex3f(TableY/16.0, 0, TableY/8.0);//2
                            glColor3f(0.0, 1.0, 0.0);
                            glVertex3f(TableY/16.0, -TableY/8.0, 0);
                            glColor3f(0.0, 0.0, 1.0);
                            glVertex3f(TableY/8.0, -TableY/8.0, 0);
                            glColor3f(1.0, 0.0, 0.0);
                            glVertex3f(TableY/16.0, 0, TableY/8.0);//3
                            glColor3f(0.0, 1.0, 0.0);
                            glVertex3f(TableY/8.0, -TableY/8.0, 0);
                            glColor3f(0.0, 0.0, 1.0);
                            glVertex3f(TableY/8.0, TableY/8.0, 0);
                            glColor3f(1.0, 0.0, 0.0);
                            glVertex3f(TableY/16.0, 0, TableY/8.0);//4
                            glColor3f(0.0, 1.0, 0.0);
                            glVertex3f(TableY/8.0, TableY/8.0, 0);
                            glColor3f(0.0, 0.0, 1.0);
                            glVertex3f(TableY/16.0, TableY/8.0, 0);
                        glEnd();
                        glPopMatrix();

                        glPushMatrix();                     //Net
                        glBegin(GL_POLYGON);
                            glColor3f(1.0, 1.0, 1.0);
                            glVertex3f(TableY/16.0, 0.0, TableY/8.0);
                            glVertex3f((TableX - TableY/16.0), 0, TableY/8.0);
                            glVertex3f((TableX - TableY/16.0), 0, 0);
                            glVertex3f(TableY/16.0, 0.0, 0.0);
                        glEnd();

                        glPopMatrix();
                    glPopMatrix();
                glPopMatrix();
            glPopMatrix();
        glPopMatrix();
    glPopMatrix();
}

//Display Callback Function
void MyDisplay( ){
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity( );
    gluPerspective(60.0, (GLfloat)width/height, 0.0, 10.0);

    //Change Viewpoint by Mouse Position
    gluLookAt((float)(ViewX - width/2)/width*20 + 2.5, (float)(height/2 - ViewY)/height*20  + 2.5, ViewZ, TableX/2, TableY/2, TableHeight, 0.0, 1.0, 0.0);

    printf("eyex = %f , eyey = %f , eyez = %f \n",(float)(ViewX - width/2.0)/width*10, (float)(height/2 - ViewY)/height*10, (float)ViewZ);

    DrawTable();    //Draw Table

    glutSwapBuffers();  //for 'Double Buffering'
}

//for Reshape Window
void MyReshape (int w, int h){
    width = w;
    height = h;

    printf("width = %d, height = %d \n", width, height);

    glViewport (0, 0, (GLsizei) w, (GLsizei) h);
    glMatrixMode (GL_PROJECTION);
    glLoadIdentity( );
    glOrtho (-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
}

//Main Function
int main(int argc, char** argv){
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE);
    glutInitWindowSize(width, height);
    glutInitWindowPosition(200, 200);
    glutCreateWindow("OpenGL Sample Drawing");
    glClearColor(0.4, 0.4, 0.4, 1.0);
    InitLight();            //set Light Setting

    glutDisplayFunc(MyDisplay);
    glutMouseFunc(MyMouseMove); //get Mouse Position, to Change Viewpoint
    glutMotionFunc(MyMotion);   //get Mouse Position, to Change Viewpoint
    glutReshapeFunc(MyReshape);
    glutMainLoop( );
}

最佳答案

gluPerspective() 的第三个参数应为非零、正且小于第四个参数:

#include <GL/glut.h>
#include <stdio.h>

float TableX = 5.0; //Table's X size
float TableY = 8.0; //Table's Y size
float TableHeight = 2.0;//Table's Height

int ViewX = 400/2;        //for Change Viewpoint by Mouse position 
int ViewY = 400/2;
int ViewZ = 9;

GLUquadricObj* cyl;

void InitLight( ){
    glEnable(GL_DEPTH_TEST);    //for opaque
    glEnable(GL_NORMALIZE);     //normalize
    glEnable(GL_SMOOTH);        //for smooth color
    glEnable(GL_LIGHTING);  //light setting
    glDepthMask(GL_TRUE);

    GLfloat ambientLight[] = {0.3f, 0.3f, 0.3f, 1.0f};
    GLfloat diffuseLight[] = {0.7f, 0.7f, 0.7f, 1.0f};
    GLfloat specular[] = {1.0f, 1.0f, 1.0f, 1.0f};
    GLfloat specref[] = {1.0f, 1.0f, 1.0f, 1.0f};
    GLfloat position[]={400.0, 300.0, -700.0, 1.0};

    glLightfv(GL_LIGHT0, GL_AMBIENT, ambientLight);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuseLight);
    glLightfv(GL_LIGHT0, GL_SPECULAR, specular);
    glLightfv(GL_LIGHT0, GL_POSITION, position);

    glEnable(GL_LIGHT0);
    glEnable(GL_COLOR_MATERIAL);

    glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
    glMateriali(GL_FRONT, GL_SHININESS, 128);
}

//Get Mouse Position to Change ViewPoint
void MyMouseMove(int button, int state, GLint X, GLint Y)
{
    //Get Mouse Position X, Y
    ViewX = X;
    ViewY = Y;

    glutPostRedisplay();
}

//Get Mouse Position to Change ViewPoint
void MyMotion(GLint X, GLint Y)
{
    //Get Mouse Position X, Y
    ViewX = X;
    ViewY = Y;

    glutPostRedisplay();
}

//Draw Table
void DrawTable(){
    glPushMatrix();
    glTranslatef(0.0,0.0,1.0);
    glColor3f(0.5, 0.25, 0.0);
    cyl = gluNewQuadric();
    glRotatef(-90,1.0,0.0,0.0);
    gluCylinder(cyl, 0.2, 0.2, TableHeight, 10, 20); //Leg of Table 1
    glPushMatrix();
    cyl = gluNewQuadric();
    glTranslatef(TableX,0.0,0.0);
    gluCylinder(cyl, 0.2, 0.2, TableHeight, 10, 20); //Leg of Table 2
    glPushMatrix();
    cyl = gluNewQuadric();
    glTranslatef(0.0, TableY, 0.0);
    gluCylinder(cyl, 0.2, 0.2, TableHeight, 10, 20); //Leg of Table 3
    glPushMatrix();
    cyl = gluNewQuadric();
    glTranslatef(-TableX,0.0,0.0);
    gluCylinder(cyl, 0.2, 0.2, TableHeight, 10, 20); //Leg of Table 4
    glPushMatrix();
    glTranslatef(TableX/2.0, -TableY/2, TableHeight);
    glScalef(TableX+0.5, TableY+0.5, 0.5);
    glutSolidCube(1);                           //Board of Table
    glPopMatrix();

    glPushMatrix();                         //triangular1 (Beside of Net)
    glTranslatef(0, -TableY/2, TableHeight);
    glBegin(GL_TRIANGLES);
    glVertex3f(TableY/16.0, 0, TableY/8.0);//1
    glVertex3f(0, TableY/8.0, 0);
    glVertex3f(0, -TableY/8.0, 0);
    glVertex3f(TableY/16.0, 0, TableY/8.0);//2
    glVertex3f(0, -TableY/8.0, 0);
    glVertex3f(TableY/16.0, -TableY/8.0, 0);
    glVertex3f(TableY/16.0, 0, TableY/8.0);//3
    glVertex3f(TableY/16.0, -TableY/8.0, 0);
    glVertex3f(TableY/16.0, TableY/8.0, 0);
    glVertex3f(TableY/16.0, 0, TableY/8.0);//4
    glVertex3f(TableY/16.0, TableY/8.0, 0);
    glVertex3f(0, TableY/8.0, 0);
    glEnd();
    glPushMatrix();                     //triangular2 (Beside of Net)
    glTranslatef(TableX - TableY/8.0, 0 , 0);
    glBegin(GL_TRIANGLES);
    glColor3f(1.0, 0.0, 0.0);
    glVertex3f(TableY/16.0, 0, TableY/8.0);//1
    glColor3f(0.0, 1.0, 0.0);
    glVertex3f(TableY/16.0, TableY/8.0, 0);                         
    glColor3f(0.0, 0.0, 1.0);
    glVertex3f(TableY/16.0, -TableY/8.0, 0);
    glColor3f(1.0, 0.0, 0.0);
    glVertex3f(TableY/16.0, 0, TableY/8.0);//2
    glColor3f(0.0, 1.0, 0.0);
    glVertex3f(TableY/16.0, -TableY/8.0, 0);
    glColor3f(0.0, 0.0, 1.0);
    glVertex3f(TableY/8.0, -TableY/8.0, 0);
    glColor3f(1.0, 0.0, 0.0);
    glVertex3f(TableY/16.0, 0, TableY/8.0);//3
    glColor3f(0.0, 1.0, 0.0);
    glVertex3f(TableY/8.0, -TableY/8.0, 0);
    glColor3f(0.0, 0.0, 1.0);
    glVertex3f(TableY/8.0, TableY/8.0, 0);
    glColor3f(1.0, 0.0, 0.0);
    glVertex3f(TableY/16.0, 0, TableY/8.0);//4
    glColor3f(0.0, 1.0, 0.0);
    glVertex3f(TableY/8.0, TableY/8.0, 0);
    glColor3f(0.0, 0.0, 1.0);
    glVertex3f(TableY/16.0, TableY/8.0, 0);
    glEnd();
    glPopMatrix();

    glPushMatrix();                     //Net
    glBegin(GL_POLYGON);
    glColor3f(1.0, 1.0, 1.0);
    glVertex3f(TableY/16.0, 0.0, TableY/8.0);
    glVertex3f((TableX - TableY/16.0), 0, TableY/8.0);
    glVertex3f((TableX - TableY/16.0), 0, 0);
    glVertex3f(TableY/16.0, 0.0, 0.0);
    glEnd();

    glPopMatrix();
    glPopMatrix();
    glPopMatrix();
    glPopMatrix();
    glPopMatrix();
    glPopMatrix();
}

//Display Callback Function
void MyDisplay( ){
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode (GL_PROJECTION);
    glLoadIdentity( );
    double width = glutGet( GLUT_WINDOW_WIDTH );
    double height = glutGet( GLUT_WINDOW_HEIGHT );
    gluPerspective(60.0, (GLfloat)width/height, 0.01, 100.0);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity( );

    //Change Viewpoint by Mouse Position
    gluLookAt((float)(ViewX - width/2)/width*20 + 2.5, (float)(height/2 - ViewY)/height*20  + 2.5, ViewZ, TableX/2, TableY/2, TableHeight, 0.0, 1.0, 0.0);

    printf("eyex = %f , eyey = %f , eyez = %f \n",(float)(ViewX - width/2.0)/width*10, (float)(height/2 - ViewY)/height*10, (float)ViewZ);

    DrawTable();    //Draw Table

    glutSwapBuffers();  //for 'Double Buffering'
}

//Main Function
int main(int argc, char** argv){
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE);
    glutInitWindowSize(400, 400);
    glutInitWindowPosition(200, 200);
    glutCreateWindow("OpenGL Sample Drawing");
    glClearColor(0.4, 0.4, 0.4, 1.0);
    InitLight();            //set Light Setting
    glEnable( GL_DEPTH_TEST );

    glutDisplayFunc(MyDisplay);
    glutMouseFunc(MyMouseMove); //get Mouse Position, to Change Viewpoint
    glutMotionFunc(MyMotion);   //get Mouse Position, to Change Viewpoint
    glutMainLoop( );
}

关于c++ - OpenGL _ Front 对象被 Back 对象覆盖。所以看不到，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/16104846/

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这个问题已经有答案了: Why are these constructs using pre and post-increment undefined behavior? (14 个回答) 已关闭 6

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c++ - OpenGL _ Front 对象被 Back 对象覆盖。所以看不到