The OIIO TextureSystem looks up texture, for any number of channels. It's not 
clear that anybody uses or needs that functionality. OSL, for example, 
inherently does only 1, 3, and 4 channel lookups.

If limiting TextureSystem lookups to 4 channels per call would result in 
simplification and/or speed up, would anybody have objections to making such a 
change?

(For the odd application that needs a >4 channel lookup, it could always do it 
with a loop of batches <= 4 and increasing 'firstchannel'. But I suspect that 
needing >4 channels is very rare, enough to make it worth this extra trouble in 
order to speed up the common case and simplify the code.)

I'm in the middle of implementing SIMD speedups to texture lookups (for 
example, using SSE for 3 & 4 channel lookups to process the channels all at 
once), having good luck so far and wondering how far to push this.

--
Larry Gritz
[email protected]



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