@Gwyn: Great comment! Of course, I'd expect no less from you. But no pressure. I remember when the OLD lighting model caused a lot of grief due to sheer performance slowdowns and "light lag" scares. My own system at the time (powered by a now-weak Ti4200) was crippled in many locations with oodles of local lights, so I selectively turned it on and off. (I also remember when we had shadows for objects, but that's another thing…)

One can imagine an angry mob descending on a facelight-wearer. A truely "only in Second Life" situation!

What's happening with "glow" is interesting… all of this, really, is similar to some music production experiences: years ago, when virtual studio instruments (aka software synths) were introduced, CPU power was very limited compared to today. Of course you could play a few realtime, but to play more tracks, an ingenious workaround was devised: add a FREEZE mode to prerender certain tracks so that they couldn't be changed, but that CPU load would go down. In Second Life to some degree, prebaking is the same, with the exception that we don't have more advanced, dynamic lighting models YET… but Runitai Linden's work with SSAO looks exciting, and there'll be more to come: http://www.kittenlulu.com/?p=588

I should emphasize: WindLight renders our avatar meshes more accurately; it exposes their archaic-ness. Remember when we used to have a separate "Avatar Vertex" checkbox? Well, previously, avatars were lit *differently* than the rest of the scene, but now, that's been streamlined. I believe it was BigPapi Linden who noted our avatars use way more polygons than they should (he comes from a rich background in optimizing game content for performance). So the problem here is not so much changing how WindLight affects avatars as improving avatar meshes — since the former is a newly-updated part of the whole pie, whereas the latter hasn't fundamentally changed in years.

@Sable: Good observation; but I believe it's actually a light, not texture baking.

It's within LL's power to make this an option in the preferences menu such that it can always be applied to all AVs within the client's field of view.

That way, if you want to see facelit people in addition to the 'dynamic' lighting effects that builders create, you can. If you would rather not see people this way, then you should have the option of turning the preference off.

It's not a peaceful issue. When the new lighting model came out, and even in spite of the limitations on just 6 lights on a scene, builders cleverly used lights to give proper "atmosphere" to the buildings. Before facelights became popular, I remember people like Scope Cleaver or Damien Fate showing me very detailed use of ambient lights. These builds looked gorgeous — as you walked across them, lights would subtly illuminate the scene realistically as you progressed through the several rooms. Some themed buildings even fared better: say, a hidden mountain cave where you're holding a light-enabled lantern, and would see eerie things as you progressed through tunnels with the day of light here and there showing through cracks on rocks, etc.

Then people started to wear facelights, and all the magic of these buildings disappeared. In fact, they became ugly, uninteresting, dull, and some clients even complained! In fact the only thing that happened was that a small group of 2-3 avatars wearing multiple facelights just stole all the lights in the scene. For them — and anyone else visiting those places — the scene became uninteresting, and they complained.

So what did builders do? Since they cannot control who's wearing facelights (or how many are wearing them), the choice is to use the "glow" attribute of prims, and 'bake' textures to look like they're being illuminated. Light and shadows become textures, and not dependent on the lighting model. Sure, it means that scenes don't look "dynamic", but they're just "scenario". You can still do some pretty effects that way, but it's far less realistic than using "real" ambient lights. But it's the only choice left!

It also raises the cost of creating complex environments — 'baking' textures to 'fake' lights and shadows require setting them up in something like Maya or 3DS and projecting lights and shadows, and then do cutting & pasting, bit by bit, into SL. Or, as an alternative, shadows and light elements become extra, useless prims, just to be able to give some slight 'illusion' of ambient illumination. We always had this choice in SL, of course.

It also means that "dark environments" will get less and less attention, since people wearing facelights will cause pools of light to spill over the scene. Yes, of course, there are better facelight designers than others, and it's not so awful in some cases. It still looks strange. Facelights work far better during the day, but people use them all the time.

It's a tricky issue, then. Lights were intended to be used by builders, not by avatars in their vanity. But the latter case has triumphed, because Windlight renders the avatar meshes in such a weird way. Vanity, in SL, tends to triumph always over building — people buy many more clothes than furniture in SL, for instance — so it's quite unlikely that this will change. OpenGL will not change the number of available lights (to, say, a 100!) in the near future due to the raw processing power needed to calculate ambient lighting, so there is just one option left:

Make avatar meshes render beautifully in Windlight

Here is a more quantitative analysis to prove the 30 meter diameter resulting from the additive effect in windlight for 6 facelights on max (old "bad" style facelight settings so many people still use):

http://www.flickr.com/photos/20921558@N07/2485750536/
http://www.flickr.com/photos/20921558@N07/2485750198/
http://www.flickr.com/photos/20921558@N07/2485749844/
http://www.flickr.com/photos/20921558@N07/2484962483/