Re: Draw a node twice

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Orad Hi-Tec Systems (orad_u++at++netvision.net.il)
Sun, 09 Feb 1997 13:03:52 +0200


Angus Dorbie wrote:
>
> What about two channels and traversal masks?

This way you would need to traverse all the non-leaf nodes twice.

(from man pfChannel, pfNodeTravMask area:

  PFTRAV_DRAW
               Node is completely ignored. Both cull and draw
traversals skip
               the node and its children.

)

Typically, there is a small number of multi-pass nodes (for special
effects
like multi-layered texture, bump-mapping), relative to a large and deep
scene-graph. This would cause a large overhead. For example, all the DCS
matrix calculations will be performed twice, all the culling
calculations
for non-leaf nodes will be performed twice, etc.

Ran Yakir wrote:
> Maybe this could be a nice addition to Performer's API. You could have a
> pfNodeTravMode function of pfNodeMPassMode that will set the number of
> passes for a specific node, and some parameters for the multipass (like,
> when to draw the second pass - right after the node gets drawn, or at
> the end of the normal scene).
>

and a user callback before every pass to change the GL state...

Moshe Nissim
Orad Hi-Tec Systems
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