Creating a sculpty without starting from a basic shape? (Blender)

As far as I've been able to tell the only way to make a sculpty is to start from a basic shape (A sphere, cylinder or such, I've been using Domino Marama's script) and then deform it to get your final sculpty.

But if you look at most tutorials on the web (Like this one for example! http://blenderartists.org/forum/showthread.php?t=99944 ), it seems like usually they start off with a plane or a cube and then extrude it as needed to get the final model.

I was wondering if it's at all possible to make somethingl in this way that's suitable for importing as a sculpty? I'd really appreciate any advice, thank you!

The short answer is no. Sculpties can't really be based upon extrusions. The reason is that every sculpty is essentially nothing more than a flat rectanglular plane that has been bent and folded in 3D space to create the appearance of more complicated geometric shapes. Think of it a bit like wrapping paper around a gift box. No matter what 3D shape you force the paper into while it's wrapped, it's still just a piece of paper, nothing more than a basic rectangle when examined in 2D.

Or perhaps a better metaphor is origami. If you know what you're doing as an oragami artist, you can simulate all kinds of 3D objects with nothing more than a 2D square of paper, folded in 3D space. But no matter how you fold it, the paper itself is never anything more than just a simple square. You can unfold it at any time, and you'll see that the 2D structure has not changed in any way, only its orientation in 3D space.

Extrusions are totally different. When you extrude edges to create new faces, as is exampled in your link, the result is no longer based upon a single rectangle. Imagine trying to add another piece of paper to your origami model by grabbing hold of the edge of the first piece, and pulling. Obviously, that would be physically impossible.

This is one of the crucial ways in which sculpties differ from typical mesh models. Sculpties are created by clever reorientation of a simple pre-existing structure. Aribtrary meshes are more often created by adding and subtracting new structure. There's a huge difference there.

SL does not support arbitrary meshes at this time. One day it will, but now, and likely not in the near future. For now, it only supports a few basic types of geometry that it already knows about. Since it has always known how to make 2D planes, it wasn't much of a leap to get it to fold those planes in 3D to create sculpties. Getting it to work effectively with completely arbitrary meshes is a very different animal.

Ah ok, I suspected that was probably the case but I thought maybe there was some way of mapping the extruded model in a way that you could make a sculpty out of - to use your metaphor, making a model and then wrapping the paper around it rather than making the model out of the paper itself.

Bit of a shame, thanks for your quick answer though! At least I know now

Just to clarify, if you're good with UV mapping, and you're careful, you could certainly make your suggestion work in some cases. That eyelid is essentially a cylinder, for example. So if you were careful to build it with perfectly rectangular mapping, it wouldn't really matter that it happened to have come into existence through extrusion instead of deformation. But since it would almost always be faster, easier, and far less risky just to start with a cylinder in the first place, there's not a whole lot of point in going the extrusion route.

In short, deforming of planes will always work. Extrusions will work only sometimes, and only under extremely constricted methodology. It makes the most sense to go with what always works.

Ah I see, hm, well that's good to know! I'm not good with UV mapping so it's probably not an option Good to know that it IS at least possible though, maybe in the future, but for now as you say it's probably best to stick with the reliable method! Thanks again for your help!

One thing to bear in mind is that my scripts present a simplified version of sculpties with the emphasis on making LOD management and modeling easier. This is done primarily by using quads, but when rendered in Second Life, triangles are used. This is particularly a problem with inner extrusions (such as box modeling uses) as they guarantee that you can't get a clean UV map to bake the sculptie.


http://dominodesigns.info/images/second_life/sculptie_extrusion.png

As you can see, the top left and bottom right corners of the extrusion are going against the direction of the triangles on the sculptie on the left.

So while some techniques can be used to make sculpties from scratch, inner extrusions is not one that will give acceptable results. Things like extruding a single point to create a profile for the spin tool will work as these give the equivalent of a subdivided plane which can be uv mapped appropriately.