Selection problem

[Tindor]

Hi, I'm having a problem when I try to use the select function. I always get hits=0, it doesn't matter where I click. Here's the code, but it has changed several times.Originally I followed the tutorial in the Red book and several other places,but after that I have changed the code several times. Here's the latest version:

void MainWindow::selectElement()
    {
        GLuint select_buf[SELECT_BUFSIZE]; 
        GLuint hits;
        GLint viewport[4];
 
        glGetIntegerv (GL_VIEWPORT, viewport); 
 
        glSelectBuffer(SELECT_BUFSIZE, select_buf);
        glRenderMode(GL_SELECT);
        glInitNames();
        glPushName(-1);
int height, width;
       height=w->height();
        width=w->width();
 
        gluPickMatrix((GLdouble)mouseX, 
                 (GLdouble)viewport[3]-mouseY, 
                5.0, 5.0, 
                 viewport);
 
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
        GLfloat x= (GLfloat) width/height;
       glFrustum(-x,x,-1.0,1.0,1.0,1.0);
        glMatrixMode(GL_MODELVIEW);
        for(int i = 0; i < spisyk.size(); i++){
        glLoadName(i);
        spisyk[i]->draw();
        }
 
 
       glPopMatrix();
       glFlush(); 
        hits = glRenderMode(GL_RENDER); 
 
        GLuint hitnames[256];
        unsigned int hi = 0;
        GLuint name, numnames, z1, z2,j=0;;
 
        if (hits>0)
 
            {
 
        numnames = select_buf[j++];
        z1 = select_buf[j++];
        z2 = select_buf[j++];
        int i=0;
        while(i<numnames)
        {
            hitnames[i]=select_buf[j];
            cout << hitnames[i]<< endl;
            i++;
        }
 
        }
 
        cout << hits << "  hitа  "<< endl;
    }

Any help will be greatly appreciated.

[mikael_aronsson]

You call gluPickMatrix(...) before you call glMatrixMode( GL_PROJECTION) and that looks a bit odd to me.

[Tindor]

Thanks, it works now

[Relic]

You also push the projection matrix but pop the modelview matrix.
If you had added glGetError during debugging you should have received stack underflow errors immediately and overflow errors after you called this more often than the projection matrix stack size which is rather small.

[Tindor]

Thanks again !
I'm quite new to OpenGL and didn't even know about the glGetError.