Does something worn by an avatar automatically become insubstantial?

Forgive my ignorance, as I'm only just starting to play with scripting. I've noticed that when a physical object is worn by an avatar, it becomes phantom so the avatar components can pass through things. For example, a friend of mine has a Jabba the Hutt avatar that is very, very large, but phantom, so he can actually move the avatar and hide other people within his bulk.

My question is, does something worn by an av automatically become phantom? I would like to create an armored box that sits on top of the avatar and protects it from gunfire, but which is completely physical -- a way of working my slowly up to creating a tank, of sorts. Is this possible, or does something worn always become phantom?

Yes it does, I believe this has to do with simplifying the math and physics involved in managing avatars on the grid. Its a lot easier to deal with the bounding rectangle than to try and sort out all the bits hanging off of them.

If you want to do what you're thinking your best bet is to rez it as an object/vehicle in world and not as an attachment.

Effectively, yes. It's no longer able to provide physical collisions with other objects.

Would it be possible to put both a vehicle script and a gun script into a vehicle (or parts linked to a vehicle), such at the the avatar riding in the vehicle would also be able to shoot from mouselook? Obviously this is done in more advanced ships, such as the "Naboo starfighter" I got in a box of freebies. Can the vehicle script and gun script coexist in the same prim, I guess I'm wondering?

yes. It's actually best to merge the gun script and vehicle script into a single script. If you look at any gun it is at it's bare bones a llRezObject() command fired from a mouse click. since mouse clicks are very very rarely used in vehicles, it is a simple matter to insert the gun code into the control part of the vehicles.

Yes.

What effectively happens is that the moment you wear it, it leaps into a mysterious demiplane called Attachment World. Every attachment point has its own, different Attachment World.

When SL draws your avatar, for each attachment point, it draws the contents of the appropriate Attachment World centred around the attachment point. But that's all it does - draw them. They are still in fact in Attachment World and thus can't interact in any way with anything on the actual grid.

I like the "Attachment World" concept, but it's messier than just being unable to interact with the grid "in any way": attachments can sense stuff and rez stuff and do physics on stuff, and probably lots more. For the purposes of contained scripts, the attachment kinda assumes the agent's orientation and mass. I wish someone who really knew about attachments could edit : I think there's a fair bit of occult attachment lore that's not covered there.

amen to that lol