convex hull, land impact, primcount.. wtf?

[Celestia Crystal]

so a while ago I noticice that a sim I'm estate manager on was getting alarmingly low on prims I decide to save the day and  tell the builder about the whole convex hull  jobbie. What happens next alarms me. 

 

We try to convert a building with no  sculpts or  tortured prims or scripts into a convex hull.  The land impact doesn't drop and 1k prims get returned. 

We sort out the issue and  I start to worry.  I make a box out of prims.   one prim perside, top, bottom sides..   .. a 6 prim object.  Link it. Turn it into a convex hull.  it drops to 3 land impact.  Woot.  ... then I press  ctrl-shift 1.  14244 objects on the sim. .. .. make the  convex hull  prim physics ..  14244 objects.  ...  find a larger building.   convert it from a land impact of 21 to land impact of  11 using the convex hull methoid  

.. 14244 objects listed in stats .. 

 

my question for this is, does the "convex hull trick"  even work  or does it make your sim lie to you?  The "objects"  under the sim stats windiw is roughly 2k more than what showes up in about land (which I'm told is because of our prim bonus modifier that we had to enact ..  our parcels were for  media reasons not prim reasons )   and that made  "about land"  read incorrectly. .. but this makes me ask the question .. What the hell does land impact mean in reagards to the ammout of available prims on your land?  In our case it seemed to do absoutly nothing and I'm completly  confused by this 

[Jenni Darkwatch]

prim count is  just that. How many prims are on a parcel.

Land impact counts against your land allowance. In laymans terms, land allowance is the good old "prims allowed on this parcel".

Convex hull can lower land impact but doesn't have to. With the latest server rollout it's supposed to be less dangerous to switch entire builds to convex hull, but there used to be a bug where LI would briefly jump before settling down. Scripted objects generally _never_ benefit from convex hull. One script in the entire linkset pretty much means LI = prim count, if not higher.

In the build floater you can check LI per object, and whether or not changing the physics type will do anything. Just open the more info floater and check download weight, physics weight and server weight. The highest of the three is the LI. Changing to convex hull only changes the physics weight, usually lowering it. If the download weight is already as high or higher than the number of prims in the linkset, you're not going to see any benefit.

[Celestia Crystal]

okay. Well in that case how can you tell what ammount of land impact you are allowed to have?  it used to be something arroudn 15000 prims but  with the new system I have no way of knowing how close we actually are to our limit 

[Innula Zenovka]

You're allowed objects on a sim or parcel up to a particular total land impact.   Since "legacy objects" (objects made from prims, not mesh, and which have all the component prims set to prim physics shape prim) have a land impact equivalent to the number of prims from which they are made, it doesn't make a difference.

If, however, the objects have any components set to prim physics shape convex hull or prim physics shape none, the LI for the object may be more or less than the total number of prims.   It's very dangerous, I've discovered, to combine prim physics shape prim with none or convex hull -- that can send the LI through the roof.   Far safer to set everything to convex hull or none (the root has to be convex hull).

So the short answer to your question is the LI you're allowed is exactly the same figure as the Prim Count you used to have (and has been for several months, at least).     It's just that the LI you are using may not be the same as the Prim Count you used to be using.   But you can still see what you've got left by looking at About Land.

[Dilbert Dilweg]

I like using the trick to set the child prims of a linked object to none. That removes the land impact from the child prim.. and only the root prim will have the land impact... The linked child prims set to none will be phantom with no physics. Only the root object will have the prim physics. you will walk thru the ones set to NONE.

That comes in handy when you make a book case with lots of modeled books. the book case can be the root prim with the physics while the stack of books have none.... Pretty slick

Rez 2 boxes and link them together. set the child prim to none and the LI will be 1

 

So if it is helpful to set the linked child prims to none then go for it.. Like lamps on the wall etc...

[Celestia Crystal]

Well the whole sorce of this issue is that according to About land we're using something arroudn 12000 prims on the sim, but according to ctrl-shift-1 we're using 14000 ish.   this  2k prim difference has  us woriried. We have no way of  telling wether about land is correct or  ctrl-shift-1 is right, given that  when I've  convered simple  muilti-prim objects into  convex hulls, their  land impact goes down but  "objects" under  ctrl-shift-1 remains the same. someong from linden labs says that  it's because we have the "prim bomus" sent to  5 beccause  we were using parcels to prevent media leakage but didn't want to limit prims on any particular parcel, but instead  use the whole sim's alotment accross the whole sim 

The core question of my question is if I have a prim object that I convert to convex, and  it reduces  land impact from 40 to 20, can i actually rez 20 more prims, or  not, and how do I tell for sure  how much I have free, given that a LL representitive told us "about land" is unreliable? 

[Innula Zenovka]

That's a good question.   In my experience, for what it's worth, the figures given in About Land for Parcel Land Capacity and Parcel Land impact are the ones to go on, but I don't know for certain.

Certainly, though, you can now rez objects up to the total land impact the parcel/sim can accommodate.  That might be more or less than the total number of prims you're using, but it's the LI that counts.   I know this because I've made test objects containing horribly contorted toruses, in order to give an artificially high LI , and managed to make objects comprising 2 or 3 prims that I can't rez because their LI is over 900.

[Kwakkelde Kwak]

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Innula Zenovka wrote:

That's a good question.   In my experience, for what it's worth, the figures given in About Land for Parcel Land Capacity and Parcel Land impact are the ones to go on, but I don't know for certain.

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I don't have any proof either, but that is my experience aswell. "Objects" in the statistics bar means something else I think, although I can't find what exactly.

 

[Jenni Darkwatch]

It appears to me that the CTRL+SHIFT+1 object count is literally the "object" count and thus has nothing to do with land impact (or land capacity). I've done a little bit of experimenting, and the object count goes up according to "prims" rezzed, regardless of prim type.

About Land and build floater both show Land Capacity, which equates to land impact.

Additionally, About Land and the build floater only show capacity for parcels owned on the sim, whereas the statistics floater shows the count of the entire sim. Which I suppose explains why some sims have >18k objects on them...

[Kwakkelde Kwak]

How obvious:) That must be it.

[Innula Zenovka]

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Dilbert Dilweg wrote:

I like using the trick to set the child prims of a linked object to none. That removes the land impact from the child prim.. and only the root prim will have the land impact... The linked child prims set to none will be phantom with no physics. Only the root object will have the prim physics. you will walk thru the ones set to NONE.

That comes in handy when you make a book case with lots of modeled books. the book case can be the root prim with the physics while the stack of books have none.... Pretty slick

Rez 2 boxes and link them together. set the child prim to none and the LI will be 1

 

So if it is helpful to set the linked child prims to none then go for it.. Like lamps on the wall etc...

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That's accurate as far as it goes, but it's not the full story.    As the KB article on Calculating Land Impact explains,

 

• For each object in the Second Life world, Second Life compares three important performance factors: download weight, physics weight, and server weight. It then chooses the highest of these weights and assigns it to the object as that object's land impact rating.

So by setting physics type to none for all the child prims, you'd effectively take physics weight out of the frame by clamping it to the physics weight of the root prim, but the LI may still -- almost certainly will -- be determined by the download weight or server weight of the object, which is to do with its size and visual complexity.

You can't link 40 toruses together, set them all to physics type none except for the root prim and expect to get a LI of 1 (I've just tried, and ended up with 20, which would probably have gone up had I cut and twisted them a bit).

[Dilbert Dilweg]

Right on good to know. I know I dont plan on linkiing 40 tauruses. As long as it works for my practical needs

[Innula Zenovka]

I realise you're not likely to want to link 40 toruses.    I was just doing that as test, which is why it was in my mind as an example.

If you link 8 standard 0.5 x 0.5 x 0.5 cubes together and set them to convex hull (a more likely scenario) you get an LI of 4, and it stays at 4 if you set the 7 children to none.