Mason D. Menninger (mason++at++milliways.jsc.nasa.gov)
Thu, 19 Mar 1998 17:32:03 -0600 (CST)
I'm still new to the Performer world, so please forgive
(but feel free to point out) any glaring errors.
I've been looking through the archives at various HUD
implementations and noticed that they seem to be based on
creating the HUD though OpenGL calls at some point in the
draw process (But I could be mistaken). I was wondering
how you would go about building a HUD based on fixed-geometry
parts brought in by a loader and attached somewhere in the
scene. Some of the immediate thoughts that came to mind were:
1) Draw the entire scene except for the HUD (possibly using
pfNodeTravMask), set-up the appropriate stencil mask, draw
the HUD portion of the scene graph. But I am uncertain
how to successfully stencil just a subgraph (especially
without clobbering the scene underneath the HUD region from
the previous draw).
2) A similar idea would be to draw the entire scene except for
the HUD, set-up four additional clip planes around the HUD
region, draw the HUD portion of the scene graph. This would
have the added benefit of being able to view the HUD from
multiple positions in the scene. But I am uncertain how to
successfully clip just a subgraph (without clobbering everything
underneath).
3) Create an overlay channel just for the HUD. But I'm not
convinced that it would be able to handle something as
complex as what I have in mind. Also, I don't know how to
implement overlays in pfPipeWindows.
Any ideas or corrections to these thoughts would be greatly
appreciated.
-Mason
mason++at++milliways.jsc.nasa.gov
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