🔒 Locked

Opengl picking

Started by beebop Apr 7, 2004 at 3:38 AM 0 replies 950+ views

Original Post

Apr 7, 2004 at 3:38 AM

I''ve got a problem with the openGl picking. When I do a glGetError(); after glLoadName or glPushName, I''ve got: GL_INVALID_OPERATION is generated if glLoadName is called between a call to glBegin and the corresponding call to glEnd. I don''t understand ?! Here my code called after a mouse event: // void myView:icking(int mouseX, int mouseY) { GLint viewport[4] ; GLuint selectBuf[32] ; GLint hits ; glGetIntegerv (GL_VIEWPORT, viewport); glSelectBuffer (512, selectBuf); (void) glRenderMode (GL_SELECT); glInitNames(); glPushName(0) ; glMatrixMode(GL_PROJECTION) ; glPushMatrix() ; glLoadIdentity() ; gluPickMatrix(mouseX, viewport[3] - mouseY, 5, 5, viewport); gluPerspective( 45.0, (GLfloat)_viewW/(GLfloat)_viewH, _camera.getDistance()*0.1f, _camera.getDistance()*20.0f ); glMatrixMode(GL_MODELVIEW); glF1CRDraw(GL_SELECT); hits = glRenderMode(GL_RENDER); processHits(hits, selectBuf); glMatrixMode(GL_PROJECTION) ; glPopMatrix(); glMatrixMode(GL_MODELVIEW); } // In the drawing function, I put my glPushName or glLoadName (not between glBegin or glEnd). When I treat number of hits, I always obtain 0 !! What could be the problem ?? Camera ? .... Thanks a lot

Crispy

Apr 8, 2004 at 6:31 AM

Simple - do not call glLoadName() between glBegin() and glEnd(). There''s only so many GL functions that can be called there (~15 if I remember correctly) and glLoadName() couldn''t logically be one of them since glBegin() and glEnd() actually define an object in OpenGL (and names can only be assigned to objects).

For instance, if you want each point you''re rendering to have a name, try:


for(int i = 0; i < n; i++)
{
glLoadName(...).
glBegin(GL_POINTS);
  glVertex(...);
glEnd();
}

note: didn''t have a look at your code


TCP - Transmission by Carrier Pigeons

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.