Default (repeat/Offsets) vs Planar can cause Lag

If Planar is used throughout a build instead of the default option does this make any difference?

I remember not so long ago that someone had posted that unless required for specific a prim that had been tortured always use default as planar can increase lag.

I'm not sure how it could cause lag. It's just substituting one mathematical formula for another. I guess anything's possible, but in the absence of any solid explanation one way or the other, I very much doubt it could make any difference at all.

If I'm wrong, hopefully someone will provide details to prove it. I'd be really surprised if that turns out to be the case, though.

They did assign planar a point in ARC, and from a bit of digging in llface.cpp it looks like they implemented planar (and the dead-code spherical and cylindrical projections) as transformations of the default. So, it's an additional function call rather than a substitution, they way they wrote it.

Excellent. Now, what exactly does that mean?

If means that if the texture is planar, a function has to be called to remap it when it's rendered. It's not exactly a huge amount of calculation, but it's a nonzero cost. It wouldn't be enough difference to scare me away from using them, but they're like every other feature in SL when it comes to lag: use them if they do what you need, skip them if it would be gratuitous.

Thanks for the info, Viktoria. I wouldn't have guessed that that's how it works, but I'm hardly an expert on things like programming.

It sounds like the cost is pretty negligible, but I would agree with you that since it's something other than zero, it's probably best not to use it haphazardly. Every little bit adds up. You said it best. If it's needed for the task at hand, then use it. If it's not, don't.