   picking problem...
  Hi,I have a problem with picking. I'll trie to discribe my situation :I have a set of display lists generated, in a 'display' function I do each time thisvoid GlScene::displayScene(){for(uint i = 0; i < m_widgets_to_display.size(); i++){glPushName(m_widgets_to_display.elementAt(i)->getPickingID());m_widgets_to_display.elementAt(i)->display(); //The display function calls the   displaylistglPopName();}}Now, that works fine. But now I want to implement picking in my scene. So every object has a 'name' (see abov the glPushName and glPopName). I do picking on the 'normal way' - see code below - and have some troubles with the result. Sometimes an object is dedected where isn't one, otherewise there isn't an object when there is one (-> the picking fails). I trie to dedect an object on mouseclick and print the result on the console.This is my picking code :void GlScene::picking(int x, int y){GLuint selectBuf[512];glSelectBuffer(512,selectBuf);glRenderMode(GL_SELECT);glInitNames();GLint viewport[4];glGetIntegerv(GL_VIEWPORT,viewport);glMatrixMode(GL_PROJECTION);glPushMatrix();glLoadIdentity();gluPickMatrix(x,viewport[3]-y,5,5,viewport);gluPerspective(60.0f, (GLfloat)viewport[2]/(GLfloat)viewport[3], 1.0f, 150.0f);glMatrixMode(GL_MODELVIEW);displayScene();int hits;glMatrixMode(GL_PROJECTION);glPopMatrix();glMatrixMode(GL_MODELVIEW);glFlush();// returning to normal rendering modehits = glRenderMode(GL_RENDER);// if there are hits process themif (hits != 0)processHits(hits,selectBuf);elsecout<<"no hits..."<<endl;}the processHits function is a 'classical one' :void GlScene::processHits (GLint hits, GLuint buffer[]){   unsigned int i, j;   GLuint names, *ptr, minZ,*ptrNames, numberOfNames;   cout<<"hits = "<<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;}  cout<<"The closest hit names are "<<endl;  ptr = ptrNames;  for (j = 0; j < numberOfNames; j++,ptr++) {    cout<<*ptr<<" , "<<endl;  }  cout<<endl;   }Is there anywone who knows what I'm doing wrong? I have tried so much and can 't find a solution.Thanx,Jan   
  Check out NeHe's Picking Tutorial! It may help you out.   ;  I've build these code with the 'Nehe picking tutorial', but I don't see what I'm doing wrong (when I compare my code with the nehe Code I don't see significant differences). Is there anyone, probably more experienced than me, who sees anything I'm doing wrong?   ;  Have you tried pushing at least one name into the stack before pushing the one that you want to identify the object you are creating?Example from gametutorials.com:glInitNames();// This clears the name stack so we always start with 0 names.// This next line is important.  If you don't push on at least ONE name,// The selection won't work.  Instead of glLoadName()/glEnd() you can use// glPushName(TheID) and glPopName();  Then you don't need to glPushName(0);glPushName(0);// This starts off the first object in the stackGLUquadricObj *pObj = gluNewQuadric();// Get a new Quadric off the stackgluQuadricTexture(pObj, true);// This turns on texture coordinates for our Quadrics// Bind the sun texture to the sun quadraticglBindTexture(GL_TEXTURE_2D, g_Texture[0]);// Bind the Sun texture to the sun// Below we call glLoadName().  We need to pass in an ID that we can check later that will// be associated with the polygons drawn next.  Here is how it works.  We call glLoadName()// and pass an ID.  Then we draw any primitives or shapes, then we call glEnd() which// stops assigning polys to that object name.  We now have a group of polygons that are// given an ID.  Our ID SUN now refers to the sun Quadric we draw below.glLoadName(SUN);// Push on our SUN label (IMPORTANT)// If we use glLoadName(), then we need to end it with glEnd().  There is a problem// though with some video cards that MUST have a glBegin()/glEnd() between// the calls to glLoadName()/glEnd().  This is strange but some cards grind// to a 2 FPS speed (VoodooCards).  Since we are using Quadrics there is// no glBegin()/glEnd() being called explicitly, so we need to fake it.  // *Remember, you only have to do this if you are using Quadrics.*  So, to fix // this we just put a empty glBegin()/glEnd() statement between each object ID passed in.glBegin(GL_LINES);glEnd();// Here we push on a new matrix so we don't affect any other quadrics.// We first translate the quadric to the origin (0, 0, 0), Then we rotate it// about the Y axis.  This gives it the spinning effect.  Then we draw the// largest of the spheres.  This represents the sun with its texture map.glPushMatrix();// Push on a new matrix scopeglTranslatef(0, 0, 0);// Translate this sphere to the leftglRotatef(SunRotation, 0, 1.0, 0);// Rotate the sphere around the Y axis to make it spingluSphere(pObj, 0.5f, 20, 20);// Draw the sunwith a radius of 0.5glPopMatrix();// End the current scope of this matrix// Now that we drew the sun, we want to end our Object name.  We call glPopName()// to do that.  Now nothing else will be associated with the SUN ID.glEnd();// Stop assigning polygons to the SUN label (IMPORTANT)