Mesh with transparent sides? How?

[Mika Deluxe]

I'm learning mesh on my own, and have so far been able to upload a decent one to Secondlife. Though I have a cute kitty avatar I bought in mesh, and noticed that when I edited it, the insides were transparent. OR.. more so selected sides were transparent. Like this:

 

As you can see, the inside of the mesh object is transparent, so it doesn't have a solid look all the way around. How is this done? I am trying to find tutorials on it but nothing seems to be out there. If you turn the nose around, you can see the solid parts:

 

Any help would be appreciated, I'm trying to learn this technique to help with some accessorie and furnature building. Please any advice! Thank you so much!

[Rolig Loon]

A mesh object has no equivalent in the natural world, because it has no insides --- just outsides.  You're often unaware of that because most mesh objects are designed as closed surfaces, so you can't navigate around their back sides easily.   Try rezzing a nice big cube, though.  Make it phantom and walk through it.  Once you get inside, you'll notice that it disappears.  You are looking at the inside --- the side that doesn't exist.  All objects in SL are that way, because they are all mesh, including your avatar.  You just never noticed before.

[Chosen Few]

To expand a little on what Rolig said, all objects in SL are single-sided.  This is typical of real-time environments, such as video games, and other virtual worlds. It's called "backface culling". Only the front of each face is drawn.  Back faces do not get rendered.

Because of this, it's best to also enable backface culling in your modeling program, so that as you're working, what you see in the program is the same thing you'll be seeing in the game.  Otherwise, you're bound to make a lot of mistakes, as it can quickly become hard to keep track of which surfaces are facing which direction.

If you want a two-sided surface, the simplest way to do that is just to duplicate the model, and reverse the normals on the new copy.

[Mika Deluxe]

Yes, I understand that part, though these pieces I am not cammed inside, meerly turned my camera around the object. The faces on this side of the piece are transparent, seems as though the builder did it that way. I am thinking perhaps they added a seam for the backside and meerly put a transparent area on the texture to handle that spot. My mind is trying to come up with how exactly this was accomplished.

[Chosen Few]

It's not a question of "inside" and "outside".  It's a question of front faces and back faces.  In Rolig's example, the back faces happen to be on the inside of the cube.  In the object you showed, they're simply the back of the model, since it's not an a fully enclosed shape.

For models that do indeed have a transparent texure applied to part, it's done the same way any other multi-texture mesh is done.  In your modeling program, assign different materials to the different sections.  When you upload the model to SL, those sections will each be able to take different textures.  If you want one section to be transpraent, put a transparent texture on that section.

That said, I'll repeat that from your pictures, and from the general nature of how these things work, it seems unlikely that a transparent textrure is indeed what you're looking at.  It's far more likely that you're simply looking at the back faces.

To illustrate the principle, try uploading a simple plane.  One side of it will be visible, and the other side won't.