Animator and picking

OpenGL Development JOGL Development
#1

Hello,

I’m trying to implement picking in a Jogl chess game.
My problem is that picking an object is like throwing a coin : sometimes I hit it and get the names I put on the name stack and sometimes not, although I’m clicking on the same spot.

I’m using the following code in my display mode :

…

public void display(GLDrawable glDrawable) {
GL myGL = glDrawable.getGL();
GLU myGLU = glDrawable.getGLU();

 if (selectMode) {
   myGL.glGetIntegerv(GL.GL_VIEWPORT, viewport);
   selectBuf = BufferUtils.newIntBuffer(BUFSIZE); 
   myGL.glSelectBuffer (BUFSIZE, selectBuf);
   myGL.glRenderMode(GL.GL_SELECT);
   myGL.glInitNames();
   myGL.glPushName(0);
   myGL.glMatrixMode (GL.GL_PROJECTION);
   myGL.glPushMatrix();
     myGL.glLoadIdentity();
     myGLU.gluPickMatrix (mouseX, viewport[3] - mouseY, 10, 10, viewport);
     myGLU.gluPerspective(60.0, viewport[2]/(float)viewport[3], 0.2, 60.0);
 }

 myGL.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
      
 myGL.glMatrixMode(GL.GL_MODELVIEW);
 myGL.glLoadIdentity();
      
 myGL.glTranslatef(0.0f, 0.0f, -dist);

 myGL.glRotatef(angleX, 1.0f, 0.0f, 0.0f);
 myGL.glRotatef(angleZ, 0.0f, 0.0f, 1.0f);
           
 /*** draw the chessboard and the pieces ***/
 myGL.glFlush();
      
 if (selectMode) {
     selectMode=false;
     myGL.glMatrixMode (GL.GL_PROJECTION);
   myGL.glPopMatrix();  
   myGL.glFlush();
   
   hits = myGL.glRenderMode(GL.GL_RENDER);
   processHits(hits, selectBuf);
 }

}

…

Is it possible, that glFlush() makes problems because I’m using the Animator class?
I don’t no, how the Animator class really works.

Oliver

#2

After testing a while I found out that this problem only occurs on Windows98 .
If I start my program with Linux, I have always a hit when clicking on an object, although I’m using the same Jogl version and the same graphic drivers (nvidia) on both Systems. ???

#3

Why not use gluUnProject instead? It works all the time for me on all systems :slight_smile:

#4

Not necessary, I’ve found the error. :wink:

It was not very clever to check the variable ‘selectMode’ two times in the display method while changing its state when pressing a mouse button.
You have to be very carefully if you are programming with threads :o

Oliver