draw callbacks

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ken sartor (sartor++at++visidyne.com)
Sun, 21 Jul 1996 12:29:11 -0500


Hi -

I am curious about how Performer handles draw callbacks. When
i render two semi transparent extended objects via a draw callback onto
a Performer scene graph, i get interesting results. If the
first object rendered in the callback is also the nearer one,
then i cannot see the portion of the second object that is behind
the first through the first one. However, the scene graph does
appear correctly thought the first object (including transparency
effects). Everything works appropriately if the first object
rendered is the more distant object.

Specifically what intrigues me is why and how Performer treats the
draw callback. Is the scene graph all rendered and then the callbacks
rendered one by one? There does not seem to be a performance penalty
for using the callbacks...

Any help on the details of what is going on here would be greatly
appreciated! References to documentation that discuss fine levels
of detail on how Performer works would also be great!

Thanks.

ken

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