Re: pfAllocChanData

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Jim Helman (jimh++at++surreal)
Tue, 11 Oct 94 11:43:00 -0700

What you describe should work. We already have an RFE on slaving
multiple ChanPassDatas together. However, two points:

1) ChanPassData is copied downstream every frame. 1000 pfCoords would
be 48K bytes * NumChan, which is a fair amount to copy. If I used
ChanPassData, I would probably put it PostFrame rather than in the
latency-critical PreFrame where it could hold off the start of the
CULL.

2) Large blocks of data are best passed by reference rather than by
value like ChanPassData does. You could do your own multibuffering
by creating several copies of FishData and passing the pointer to the
current one down in ChanPassData. Doing this properly for all
possible cases of cull/draw frame overruns is tricky, which is why
2.0 will have a new construct to support multibuffering of data.

rgds,

-jim helman

jimh++at++surreal.asd.sgi.com
415/390-1151

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