OpenGL implements a mechanism refered to as "selection" or "picking".
see chap. 12 in the red book. in essence, you place the render into
selection mode, pseudo-draw your scene (opengl doesnt actually write to
the frame buffer when in selection mode), while drawing the scene,
opengl builds a selection buffer with information identifying which
primitives were selected. this selection buffer is available to the
> I've been building my own rendering engine from scratch in Delphi and am
> looking to port my app over to OpenGL in the future. A crucial part of my
> app is allowing a user to click on a rendered object and the engine
> calculates the 3D world coordinate point of where they clicked. I assume
> OpenGL can do this. The question is how?
> There are 3 kinds of people
> Those who can count, and those who can't
+ Steven Barkdull +
+ Engineering Animation, Inc. +