c++ - 选择后 OpenGL 选择不显示任何内容

Question

所以我在一个显示列表中有 2 个立方体，我希望其中一个是可以选择的，这样我就可以改变他的颜色或类似的东西。

当我单击一个立方体时，屏幕变黑并且没有任何反应，控制台为我提供最近命中的输出，但屏幕变黑并且不显示任何内容。

这是我的 cpp 文件：

#include "glwidget.h"
#include <QDomDocument>
#include <QDebug>
#include <QFile>
#include <math.h>
#include <QString>
#include <stdlib.h>
GLWidget::GLWidget(QWidget *parent):QGLWidget(parent)
{

    camPosx = 0.0,  camPosy = 0.0,    camPosz = 1.0;
    camViewx = 0.0, camViewy = 0.0, camViewz = 0.0;
    camUpx = 0.0,   camUpy = 1.0,   camUpz = 0.0;
    camAngle = 0.0;
    camViewz = -cos(camAngle);
    camViewx = sin(camAngle);
    mode = 1;
    timer = new QTimer();
    connect( timer, SIGNAL(timeout()), this, SLOT(updateGL()) );
}

void GLWidget::initializeGL() {

    loadGLTextures();
    glEnable(GL_TEXTURE_2D);                            // Enable Texture Mapping
    glShadeModel(GL_SMOOTH);                            // Enable Smooth Shading
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);               // Black Background
    glClearDepth(1.0f);                                 // Depth Buffer Setup
    glEnable(GL_DEPTH_TEST);                            // Enables Depth Testing
    glDepthFunc(GL_LEQUAL);                             // The Type Of Depth Testing To Do
    glEnable(GL_LIGHT0);                                // Quick And Dirty Lighting (Assumes Light0 Is Set Up)
    glEnable(GL_LIGHTING);                              // Enable Lighting
    glEnable(GL_COLOR_MATERIAL);                        // Enable Material Coloring
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);  // Perspective Calculations
    buildLists(2);                                      // Creating displaylist #
    glLoadIdentity();

    timer->start(50);
}

void GLWidget::resizeGL(int width, int height) {

    //set viewport
    glViewport(0,0,width,height);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    //set persepective
    //change the next line order to have a different perspective
    aspect_ratio=(GLdouble)width/(GLdouble)height;
    gluPerspective(45.0f, aspect_ratio, 0.1 , 100.0);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

void GLWidget::paintGL() {
    glEnable(GL_DEPTH_TEST);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glLoadIdentity();

    // store current matrix
    glMatrixMode( GL_MODELVIEW );
    glPushMatrix( );

    gluLookAt(camPosx ,camPosy ,camPosz,
              camPosx + camViewx,camViewy,camPosz + camViewz,
              camUpx, camUpy, camUpz );

    if (mode == 2) {
        startPicking();
    }

    glColor3f(1.0f,0.0f,0.0f);
    glCallList(displayList[0]);
    glTranslatef(5.0,0.0,0.0);
    glColor3f(0.0f,1.0f,1.0f);
    glCallList(displayList[0]);

    if (mode == 2)
        stopPicking();
    //    glEnable( GL_LIGHTING );
    //    glEnable( GL_LIGHT0 );
    //    glScalef(10.0,10.0,10.0);
    //    glBindTexture(GL_TEXTURE_2D, texture[0]);
    //    glBegin(GL_QUADS);
    //    // Front Face
    //    glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);  // Bottom Left Of The Texture and Quad
    //    glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);  // Bottom Right Of The Texture and Quad
    //    glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);  // Top Right Of The Texture and Quad
    //    glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);  // Top Left Of The Texture and Quad
    //    // Back Face
    //    glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);  // Bottom Right Of The Texture and Quad
    //    glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);  // Top Right Of The Texture and Quad
    //    glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);  // Top Left Of The Texture and Quad
    //    glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);  // Bottom Left Of The Texture and Quad
    //    // Top Face
    //    glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);  // Top Left Of The Texture and Quad
    //    glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f,  1.0f,  1.0f);  // Bottom Left Of The Texture and Quad
    //    glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f,  1.0f,  1.0f);  // Bottom Right Of The Texture and Quad
    //    glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);  // Top Right Of The Texture and Quad
    //    // Bottom Face
    //    glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, -1.0f, -1.0f);  // Top Right Of The Texture and Quad
    //    glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, -1.0f, -1.0f);  // Top Left Of The Texture and Quad
    //    glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);  // Bottom Left Of The Texture and Quad
    //    glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);  // Bottom Right Of The Texture and Quad
    //    // Right face
    //    glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);  // Bottom Right Of The Texture and Quad
    //    glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);  // Top Right Of The Texture and Quad
    //    glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);  // Top Left Of The Texture and Quad
    //    glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);  // Bottom Left Of The Texture and Quad
    //    // Left Face
    //    glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);  // Bottom Left Of The Texture and Quad
    //    glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);  // Bottom Right Of The Texture and Quad
    //    glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);  // Top Right Of The Texture and Quad
    //    glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);  // Top Left Of The Texture and Quad
    //    glEnd();


//    // XML
//    QDomDocument doc( "AdBookML" );
//    QDomNode n;
//    QDomElement e;
//    QFile file( "test2.xml" );
//    QString s;
//    QStringList sl;


////    if( !file.open(QIODevice::ReadOnly))
////        qDebug("probleem bij het openen");

//    if( !doc.setContent( &file ) )
//    {
//        file.close();
//    }
//    file.close();

//    QDomElement root = doc.documentElement();
//    if( root.tagName() != "playlist" )
//        // qDebug("root is different");

//        //qDebug( root.tagName() );

//        // doorheen u boom lopen
//        n = root;
//    float f1, f2, f3;

//    glDisable( GL_LIGHTING );
//    glBegin(GL_TRIANGLES);
//    for(int i = 0; i< n.childNodes().length(); i++) // voor alle triangles
//    {
//        if(n.childNodes().at(i).toElement().tagName() == "triangle")
//        {
//            for(int j =0; j < 4; j++) // voor alle punten
//            {
//                e = n.childNodes().at(i).childNodes().at(j).toElement(); // e is een punt
//                //qDebug(e.tagName());
//                s = e.text();
//                sl = s.split(" ");          // opsplitsen naar het x, y , z coordinaat;
//                f1 = sl.at(0).toFloat();
//                f2 = sl.at(1).toFloat();
//                f3 = sl.at(2).toFloat();
//                if( j > 0)
//                    glVertex3f(f1, f2, f3);     // de vertex tekenen
//                if(j == 0)
//                    glColor3f(f1,f2,f3);
//            }
//        }


//    }
//    glEnd();
//    glEnable(GL_LIGHTING);


    // restore current matrix
    glMatrixMode( GL_MODELVIEW );
    glPopMatrix( );

}


void GLWidget::loadGLTextures()
{
    QImage t;
    QImage b;

    if ( !b.load( "images/redbrick.png" ) )
    {
        qDebug("Didn't found the image.");
        b = QImage( 16, 16, QImage::Format_RGB32 );
        b.fill( 1 );
    }

    t = QGLWidget::convertToGLFormat( b );
    glGenTextures( 1, &texture[0] );
    glBindTexture( GL_TEXTURE_2D, texture[0] );
    glTexImage2D( GL_TEXTURE_2D, 0, 3, t.width(), t.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, t.bits() );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
}

//Functie die display lists kan aanmaken, het aantal ( is het aantal displaylists )
GLvoid GLWidget::buildLists(int aantal)
{
    displayList = new GLuint[aantal];
    for(int i = 0; i < aantal; i++)
    {
        displayList[i]=glGenLists(aantal);                                  // Maak x Aantal displaylists
        glNewList(displayList[i],GL_COMPILE);                               //start met de eerste display list te compile
        //Hieronder moet er xml worden ingeladen
        glBegin(GL_QUADS);
        // Bottom Face
        glNormal3f( 0.0f,-1.0f, 0.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, -1.0f, -1.0f);
        glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);
        // Front Face
        glNormal3f( 0.0f, 0.0f, 1.0f);
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);
        // Back Face
        glNormal3f( 0.0f, 0.0f,-1.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);
        glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);
        // Right face
        glNormal3f( 1.0f, 0.0f, 0.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);
        glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);
        // Left Face
        glNormal3f(-1.0f, 0.0f, 0.0f);
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);
        glEnd();
        glEndList();
    }
}

//functie die zorgt dat we renderen in selectiemode
void GLWidget::renderInSelectionMode() {
    glInitNames(); //Creates empty stack

    glPushName(1); //Push a name on the stack
    //draw something
    glColor3f(1.0f,0.0f,0.0f);
    glCallList(displayList[0]);
    glPopName(); //pop a name from the stack

    glPushName(2); //Push a name on the stack
    //draw something
    glTranslatef(5.0,0.0,0.0);
    glColor3f(0.0f,1.0f,1.0f);
    glCallList(displayList[0]);
    glPopName(); //Pops a name from the stack
}


void GLWidget::startPicking() {

    GLint viewport[4];

    glSelectBuffer(BUFSIZE,selectBuf);
    glRenderMode(GL_SELECT);

    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glLoadIdentity();

    glGetIntegerv(GL_VIEWPORT,viewport);
    gluPickMatrix(cursorX,viewport[3]-cursorY,5,5,viewport);
    gluPerspective(45,aspect_ratio,0.1,1000);
    glMatrixMode(GL_MODELVIEW);
    glInitNames();
}

void GLWidget::stopPicking() {

    int hits;

    // restoring the original projection matrix
    glMatrixMode(GL_PROJECTION);
    glPopMatrix();
    glMatrixMode(GL_MODELVIEW);
    glFlush();

    // returning to normal rendering mode
    hits = glRenderMode(GL_RENDER);

    // if there are hits process them
    if (hits != 0)
        processHits(hits,selectBuf);
}

void GLWidget::processHits (GLint hits, GLuint buffer[])
{
    unsigned int i, j;
    GLuint names, *ptr, minZ,*ptrNames, numberOfNames;

    printf ("hits = %d\n", hits);
    ptr = (GLuint *) buffer;
    minZ = 0xffffffff;
    for (i = 0; i < hits; i++) {
        names = *ptr;
        ptr++;
        if (*ptr < minZ) {
            numberOfNames = names;
            minZ = *ptr;
            ptrNames = ptr+2;
        }

        ptr += names+2;
    }
    printf ("The closest hit names are ");
    ptr = ptrNames;
    for (j = 0; j < numberOfNames; j++,ptr++) {
        printf ("%d ", *ptr);
    }
    printf ("\n");

}

void GLWidget::mousePressEvent(QMouseEvent * e)
{
    if(e->button() == Qt::LeftButton)
    {
        qDebug("mouse");
        qDebug("%d",QCursor::pos().x());
        this->cursorX = QCursor::pos().x();
        this->cursorY = QCursor::pos().y();
        this->mode = 2;
    }
}

void GLWidget::keyPressEvent( QKeyEvent * e ) {

    double fraction = 0.1f;
    if(e->key() == Qt::Key_Up)
    {
        camPosz += camViewz * fraction;
        camPosx += camViewx * fraction ;
    }
    if(e->key() == Qt::Key_Down)
    {
        camPosz -= camViewz * fraction;
        camPosx -= camViewx * fraction ;
    }
    if(e->key() == Qt::Key_Left)
    {
        camAngle -= 0.05f;
        camViewz = -cos(camAngle);
        camViewx = sin(camAngle);
    }


    if(e->key() == Qt::Key_Right)
    {
        qDebug("cam angle is %f", camAngle);
        camAngle +=0.05f;
        camViewz = -cos(camAngle);
        camViewx = sin(camAngle);
    }
}

#ifndef GLWIDGET_H
#define GLWIDGET_H

#include <QtOpenGL/QGLWidget>
#include <gl/GLU.h>
#include <QImage>
#include <QKeyEvent>
#include <QMouseEvent>
#include <QTimer>
#define BUFSIZE 512

class GLWidget: public QGLWidget
{
    Q_OBJECT

public:
    GLWidget(QWidget *parent = NULL);

private:
    double camPosx,camPosy,camPosz;
    double camUpx,camUpy,camUpz;
    double camViewx,camViewy,camViewz;
    double camAngle;


protected:
    void initializeGL();
    void resizeGL(int width, int height);
    void paintGL();
    void keyPressEvent(QKeyEvent * e);
    void mousePressEvent(QMouseEvent * e);
    QTimer* timer;
    void loadGLTextures();
    GLuint  texture[1];
    GLuint  * displayList;
    void renderInSelectionMode();
    GLvoid buildLists(int aantal);
    void startPicking();
    void stopPicking();
    void processHits (GLint hits, GLuint buffer[]);
    GLuint selectBuf[BUFSIZE];
    GLdouble aspect_ratio;
    int cursorY;
    int cursorX;
    int mode;
};

#endif // GLWIDGET_H

这是没有点击一次的正常视图 http://imageshack.us/photo/my-images/233/31536776.png/

然后当点击它时，它会不断进入开始拾取并停止拾取并给出黑屏 http://imageshack.us/photo/my-images/13/14180995.png/

然后在关闭窗口后停止运行它给了我这个输出http://imageshack.us/photo/my-images/861/13486229.png/

Answer 1

可能是错误的，但看起来你没有mode在任何地方第一次鼠标单击后将 -variable 重置回 1，因此从第一次单击开始在每一帧上调用start- & -方法。stopPicking如果不是这种情况，那么您可能对 gl-states/matrix 有一些问题，在挑选后没有全部正确重置。