How to understand Object and LinkSet?

One physical object can be made up of 31 prims. But a Linkset can be 256 prims. How to understand this? What's the difference between Object and Linkset?

There's no difference between an object and linkset, at least not for any practical scripting purposes.

But there is a difference between physical and non-physical objects. The 31 priim limit only applies to physical objects, not non-physical objects.

This question would probably hve been better asked in the scripting tips forum.

Why Scripting Tips, Kidd? The question is not about writing scripts. Linking prims into linksets, and turning them physical or not, are basic functions of building. If one wants to learn how to do something more advanced with a physical object, like turn it into a vehicle or something, then of course that would be a scripting question. But that doesn't seem to be what was asked about here. Therefore, I would say this post should have been in Building Tips.

But regardless, you're right that it doesn't belong here in Resident Answers. I certainly agree with your point on that.

For the past several weeks, there has been an unusually high volume of people posting content-creation questions in Resident Answers instead of in the appropriate content-creation forums. It's really getting annoying.

It goes against my better judgment to answer your question here, Own, since it doesn't belong here, but I'll do it anyway. Here's how I'd put it:

Technically every single item in SL is an object. Prims, textures, clothing, trees, scripts, everything. Behind the scenes, the whole system is basically a giant database, and all items stored in it are objects. But usually when people use the word "object" in everyday speech in SL, they're referring only to 3-dimensional items, things made out of prims. Most people aren't talking about things like textures when they use the word "object".

For an example of how the word is meant in its most common usage, take a group of 10 prims. For as long as they are unlinked, they are 10 individual objects. But link them together, and they become one object. Unlink them, and they're 10 separate objects again.

A linkset, as its name suggests is a group of two or more prims that have been linked together. All linksets are objects, but not all objects are linksets.

As for the limitations on the amount of prims you can have in a linkset, as Kidd said, that just comes down to whether or not you want the object to be physical. Physical objects can have anywhere from 1 to 31 prims in them. Non-physical objects can have anywhere from 1 to 256 prims in them.

When objects are physical, they are affected by forces such as gravity, wind, momentum, etc. Non-physical objects are immune to these forces. Since the mathematics of calculating the effects of forces is expensive in terms of server-side computing power, the amount of prims allowed in each physical object is kept relatively low. The more prims involved, the more resource-intensive the calculations become. If a 256-prim physical object were to be allowed, it would "lag" the server a lot more than the 31-prim physicals that are allowed currently.

But now that the Havok 4 physics engine is in place, it's possible the limit might be raised. That was one of the potential benefits of upgrading from the old Havok 1, mentioned by the Lindens when the upgrade project began. We'll have to wait and see if they decide to raise it.

Sorry to continue this thread in the wrong place but what you said is interesting, Chosen. Could you go a bit farther and explain how items such as prim hair and prim skirts fit into the scheme of things, please? They often have more than 31 prims but of course they are not exactly physical. On the other hand they do respond to wind...

The wind they respond to is a part of being a flexible object. Flexibility is completely client side, and purely visual. You'll find the bounding box of the objects doesn't change, and they must be phantom to be flexible.

Physical objects however can be phantom, and the bounding box moves with the object. Physicality is server-side, and handled by the SL servers, not your client, so it actually strains the sim itself, while flexy prims will only strain your computer if anything, which is quite a bit safer technically speaking than straining the servers.

ETA:: Changed it to be correct per Chosen and Meade's corrections. Sorry, and thank you both!

Ah. thanks Keira

Oh, good question, Kaimi.

Flexible prims do appear as if they are (partially) physical, even though they're not. The effect is purely graphical, and is generated on the client side, not the server side. No actual physics are in play, so the 31-prim limit doesn't apply.

The client software (the viewer) simply monitors the forces generated by the server-side physics engine, and then draws the flexible prims approximately the way they would appear if they actually were responding physically to those forces. It's "smoke & mirrors", basically, just an illusion.

As far as the server knows, there's no such thing as flex. I thinks that all prims are always rigid. This is why fliexible prims have to be phantom. If they were to collide with things, they would do so as if they were straight, which would spoil the illusion. LL circumvented that problem by ensuring that flexis would never collide with anything.

Make sense?

Uh.. Can you check the spelling on that bit?

Sure they can. Did you perhaps mean to say physical objects cannot be flexible?

Can they really? Oops.. guess I've never tried o.o


I was under the impression that they couldn't because they'd float through the ground or something. Do they do this, or do they behave normal with the ground, but not with other prims?

I really thought that you couldn't toggle both 'physical' and 'phantom' at once. Apologies for my misunderstanding XD

This is really interesting. Both your explanations helped me to understand something I never really thought about before. I feel as if I have a slightly better understanding of the universe now.

They will drop through prims but not the ground.

You'll frequently see critters and such be physical/phantom. I have a friend who just got a a family of ducks that swim around her pool - they're physical so they can do the smooth movement and phantom so they won't get stuck or push people around. Looks a little weird when they pass thru each other but overall they're nice.

Physical/phantom is probably not something you'd want to do without using targets or buoyancy, though. Or some type of scripted movement to keep it from just dropping to the ground and sitting there.

Coolies, thank you ^_^

Very useful to know, and now I won't spout bad info trying to help XD

Well..least not _that_ particular tidbit of bad info.

Thank you for explaining and correcting ^_^

/me isn't sure she buys that. In the SL context, I've never heard anything but prims called an object. Asset is usually the term I hear to describe the SL atom...

edit: I'm a bozo - ignore this post, please.

I think of avatars and such as objects, just as in most programs for making levels and such they'd be an object.
(Talking about how in the Oblivion mod tools, Halo mod tools, etc. I've always seen characters labeled as a type of object in technical applications)

But in SL, an avatar is made up of the shape mesh then several layers of textures then whatever prims are attached. Would you call each of these pieces objects?

I wouldn't call the textures objects, but the attached prims become part of the avatar object, in my mind's view. They become part of it because they move with it, they are..well..part of it ^_^ Just like a linkset

Just like how when an avatar sits on something, it becomes part of that linkset.

This is why I was careful to say "in the SL context".

For code geeks and such, of which I'm a proud member, sure - everything everywhere in the universe can be described as some kind of object. In the context of SL though, you won't often hear an avatar being called 'object'. Or textures or shapes or anything other than something made of prims.

That was the only point - the atoms of SL are assets, not objects. I'm just poking semantics at Chosen, though.

mm..I spose yeah, most people don't use object to refer to avies at all

Then again, to me I also consider textures assets, but not much else for some silly reason...so I'm a bit skewed XD

Prims are the only asset that can actively be simulated (although scripts do have a running state as well), all other assets only ever exist on the asset server (baked textures exist only on the sim but they're not technically assets anyway ) so there's nothing inherently wrong in distinguishing between assets and actively simulated objects.

Whenever a prim/linkset is rezzed, the sim will fetch a copy of the asset data and add the object to the actively simulated set. From that point on until it's taken back into inventory (through take, return, delete, etc) the object exists only on the sim and while it can still be a carbon copy of the asset it was created from, it doesn't have to be it's an entity in its own right.

If I rez a copy chair from inventory, what I have in inventory is a reference to an asset but what's on the sim is an actively simulated object and both are distinctly different things (the asset is stored on the asset server, the object is stored on the sim).

(Attachments work the same... if you wear an attachment the visible attachment is the actively simulated object while what's still in your inventory is the asset. If you modify the attachment and tp to a different sim, the originating sim is responsible for passing the object on to the destination sim and it's only on log-off or detach that the object is uploaded back to the asset server and changes are actually made permanent in the actual asset)

Meade, if you want to talk about context, perhaps you shouldn't quote out of context, yourself.

In my very next sentence after the one you quoted, I noted very clearly that when people use the term "object" in SL, they tend to mean 3-dimensional items, made out of prims. The previous sentence merely gave the broader definition.

Ack!

Sorry - I'm just slow today.. No offense intended, Chosen.

Did I say there was anything wrong with it? I didn't even mention the word "asset" at all.

Look, while the substance of what you're saying is true, I'm wondering why you felt the need to preface it with a quote from me, as if somehow your point is at odds with mine. This distinction between assets and objects, however important it may be, really has nothing to do with anything I said in the post you quoted, nor does it answer the OP's question as asked.

If you want to broaden the discussion, that's fine. But at least make it clear that that's what you're doing, and please don't imply I said things I didn't.

No offense taken, Meade. It's all good.

If you want to call all assets "objects", which is what I gathered you were saying, then you still need a new word to distinguish an actively simulated asset on the sim from an asset that's stored on the asset server since they're very different things.

You seem to be unusually defensive on the forums lately, not everyone is "out to get you".