2D 3D projection question

[Keith W. <kw...@cs...>]

Can I easily take a pixel coordinate and determine which 3D object is
under that pixel, in other words which 3D object (or actual triangle or
trimesh I suppose) is shallowest in the z-buffer at the pixel's location?

I know Open-GL has routines for this sort of thing.  How would this be
done in QD3D or Quesa?  Or can it not easily be done?

It would be useful for a program/game I'm working on because the user
could click on parts of a rendered scene to interact with objects in the
scene, but that will only work if I can figure out what has been clicked
on, right?

I mean, I could force the user to line the camera up perfectly straight
with an object and then interact with it on the assumption that it's the
object directly ahead of the camera's forward-vector in world space, but
that's a tedious requirement to place on the user.

Thanks.

________________________________________________________________________
Keith Wiley                                kw...@cs...
http://www.unm.edu/~keithw                 http://www.mp3.com/KeithWiley

"Yet mark his perfect self-contentment, and hence learn his lesson,
that to be self-contented is to be vile and ignorant, and that to
aspire is better than to be blindly and impotently happy."
                                           --  Edwin A. Abbott, Flatland
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