OK... Anyone who's interested in building things in SL should go and check out Torley Linden's announcement of the coming of "sculpted prims."
What's a sculpted prim, you ask? I'm glad you asked that. It's one whose shape is determined by a "texture." Rather than being used to describe colors, the (R, G, B) values of the "texture" are interpreted as (X, Y, Z) displacements from a center point to a matching point on the surface of the prim. The idea is that you generate an arbitrary "genus 0" 3-D shape (i.e. one without any holes in it—it can have dents, but no holes, at least in the first version) with the program of your choice and then use something to convert it into the "texture" that the SL code interprets to generate that shape on the grid. A converter exists for Maya; more will follow for other programs ("hopefully exporters for 3ds Max, Blender, and ZBrush will be available soon").
Sculpted prims will greatly expand the available shapes for building. I'm expecting a great improvement in non-human avatars, and for that matter, the possibility of a fairly good-looking built human avatar—maybe I can finally be a giantess! XCite will have a field day with this, I'm sure, but of course (here it comes) the thing of most immediate interest to me is prim breasts.
Sculpted prims mean that a prim breast can be a single prim. This in turn implies that they can be "clothed" by being painted with a texture, just as basic clothing in SL is painted on. Right now, tops for prim breasts have to be built to match; a top that works with one maker's breasts can't be used with another. (They also have a detectable thickness, which shows up in some cases.) Textures, on the other hand, have a chance to be used in common, if a convention about orientation is established.
"Gee, you're bringing back the problem of straps," you say. Yes, I am, but I think the tradeoff is worth it. The big problem of prim breasts is that their wearers are essentially cut off from the enormous treasure of exquisite fashion developed by mainstream houses of haute couture. The ideal solution would be one that makes those tops immediately usable, but barring implementation of Prop 125 we won't get that. Next best is one that makes it so trivial to accommodate prim breast wearers that clothing manufacturers consider the effort worth it for the income gained. If prim breasts can be clothed by painting, and the same texture will work no matter whose prim breast one wears, then perhaps clothiers will consider it worth adding right and left textures for prim breasts to their products.
(OTOH, they may see that as something that simplifies the theft of their IP for minimal gain... sigh. But at least it makes it more feasible for someone to set up shop making tops for prim breasts than the current situation, which chops up an admittedly non-mainstream market into even smaller pieces.)
I note that some like the effect of bulging from too-small tops. Given an operation that composes two sculpted prim control textures (adding the corresponding displacements, along with normalization to avoid overflow), I think one could accomplish this. Along with a top you'd need a sculpted prim control texture that is (0, 0, 0) wherever the top is, and then nonzero where the top isn't, with values designed to give a realistic bulge effect. It would be nice if the composition could be done on the fly, but as long as it's possible, one could get the effect at the expense of growing one's inventory.
Sorry for going on at length... again... but sculpted prims open so many possibilities, and it's hard not to think about them. I hope that prim breast makers will consider getting together and seeing whether I'm just blowing smoke, or whether life can be made better for their customers.