Prim Count of Linked Objects

[Egon Rothschild]

I have four objects whose prim count totals under 50. However, when I link them, it jumps to over 250. Can someone explain to me why this happens? And, is there a way to make the linked prim count lower?

Thanks in advance,

Egon

 

PS One of the objects had a number of poses, etc in it's CONTENTS which I deleted prior to the link.

 

[Fritigern Gothly]

Does one or more of the links have materials on them?

[Rolig Loon]

You're not looking at "prim count"; you're looking at Land Impact, which is a very different thing.  

Read this KB article.  It will give you some ideas about how to keep your L.I. low.

[Egon Rothschild]

31 minutes ago, Fritigern Gothly said:

Does one or more of the links have materials on them?

I"m not sure what you mean by "materials on them"?

 

[Rolig Loon]

Again, read in the Knowledge Base to learn more about Materials:

 

[Egon Rothschild]

19 minutes ago, Rolig Loon said:

You're not looking at "prim count"; you're looking at Land Impact, which is a very different thing.  

Read this KB article.  It will give you some ideas about how to keep your L.I. low.

Read the article. Pretty informative.

The smaller three objects have a physics weight of .1, .1 and .6. The larger object has a physics weight of 258. The four objects when linked have a physics weight of 258.8. All four add up. Makes sense. However, the larger object has the following weights: download 47.0; physics 258.0; server 18.0; and display 34976. Yet it's land impact is only 30. Where does this 30 come from? Shouldn't it's land impact by itself be 258? What am I missing?

[Rolig Loon]

Now you're getting to the confusing part, the part that creators spend a lot of time trying to understand.  I could refer you to threads where a lot of this is discussed (like this one), but the answer is that the actual formula for computing L.I. is complicated and is constantly being modified.  The whole purpose of using Land Impact is to come up with a system that fairly represents the work load that an object places on a region's servers. Download Weight, Physics Weight, and Server Weight all factor into the equation but do not all have equal importance. They also each vary depending on whether an object uses Materials or has scripts in it, how large it is, and a number of other factors.

Most SL residents don't have to worry about all of that.  Creators do, because they want to make the highest quality products that they can while keeping L.I. as low as possible.  As a consumer, all you need to know is how to find the L.I. of an object (as you have), and what few things you can do (or avoid) to manage the total L.I. for your parcel effectively.   The most important thing is to keep your eye on quality but always check L.I. before you buy anything that you plan to rez on your land.  Beyond that, if you modify objects by linking them to each other, adding scripts or materials, or changing their sizes, always check to see what the resulting L.I. has become.  Consider making your changes in a sandbox, where you won't risk accidentally exceeding the L.I. on your own land and forcing the servers to return things that have already been rezzed.  

[Egon Rothschild]

13 minutes ago, Rolig Loon said:

Now you're getting to the confusing part, the part that creators spend a lot of time trying to understand.  I could refer you to threads where a lot of this is discussed (like this one), but the answer is that the actual formula for computing L.I. is complicated and is constantly being modified.  The whole purpose of using Land Impact is to come up with a system that fairly represents the work load that an object places on a region's servers. Download Weight, Physics Weight, and Server Weight all factor into the equation but do not all have equal importance. They also each vary depending on whether an object uses Materials or has scripts in it, how large it is, and a number of other factors.

Most SL residents don't have to worry about all of that.  Creators do, because they want to make the highest quality products that they can while keeping L.I. as low as possible.  As a consumer, all you need to know is how to find the L.I. of an object (as you have), and what few things you can do (or avoid) to manage the total L.I. for your parcel effectively.   The most important thing is to keep your eye on quality but always check L.I. before you buy anything that you plan to rez on your land.  Beyond that, if you modify objects by linking them to each other, adding scripts or materials, or changing their sizes, always check to see what the resulting L.I. has become.  Consider making your changes in a sandbox, where you won't risk accidentally exceeding the L.I. on your own land and forcing the servers to return things that have already been rezzed.  

Thanks very much, Rolig. It looks like at some point it becomes VooDoo. Gotcha

 

[Rolig Loon]

Yep, it's voodoo.

One of the things that you can do to reduce L.I. in linksets, assuming that you have permission to modify objects, is to open the Features tab in your editor and change the Physics Shape Type of one or more links.  Do this carefully, because what you are doing affects the way that the region's physics engine calculates how to handle potential collisions with the object.  If you change the shape type to Convex Hull, for example, L.I. generally increases.  Setting it to Prim reduces it.  Setting it to None usually reduces it drastically.  Each of those shapes has an advantage under different circumstances, and some are not always possible.  For example, you cannot set the shape type of a root prim to None, because that would mean that the physics engine cannot see it at all.  You can set child prims to None, though, if you don't mind making it so that you can walk right through them (Don't do this with your house!).  I have set the child prims on a lot of the trees on my land to None.

[ChinRey]

15 hours ago, Egon Rothschild said:

Thanks very much, Rolig. It looks like at some point it becomes VooDoo. Gotcha

The basic explanation for those big LI jumps isn't actually that complicated: Any object/linkset that uses some feature introduced after the "new" LI system was introduced in 2011 is calculated according to the new system. Any object/linkset that doesn't is calculated according to the old prim count system. LL did it this way to prevent the change to affect existing builds.

Some of the things that will trigger new LI calculation are:

• Meshes
• Alternative physics shapes (convex hull or "none")
• Materials
• Alpha masking
• Some script functions

Normally you want to trigger the new way since it usually gives a lower LI than the old one and in those rare occasions it backfires, you can almost always fix it by changing the physics shapes for parts of the linkset. (It is always the physics weight that causes those big LI jumps.)

The best way to do it is:

1. First make a backup of the linkset just in case something goes wrong.
2. Make sure the root of the linkset is a part that doesn't have a very high physics weight, that is not a torus, tube, ring or heavily twisted prim, and preferably one that shouldn't be phantom.
3. Select the linkset and change the physics first to Convex hull and then to None. This will give the root prim a simplified physics and make everything else phantom and the physics weight will drop like a stone.
4. Select the parts of the linkset that can't be phantom and change them to the simple Convex hull physics.
5. If there are some parts of the linkset that need more complex physics than Convex hull, select those and change the physics to Prim.

 

Edited November 7, 2021 by ChinRey

[Egon Rothschild]

WOW.

Thanks Rolig and Chin. Thanks very much. Following both of your suggestions and playing around with the Physics Shape, I found that if I set it to Convex Hull "the physics weight will drop like a stone" as Chin predicted. It went from 258 to 49! It's all Phantom but that doesn't matter. At all.

I'm somewhat embarrassed tbh. All this expertise for a stupid little problem of mine. I own land on both sides of the Heterocera Atoll Road in Sylvina at two sections. I've put up signs (speed limit, sim crossing, etc) at the road by liking them to a simple (root) sphere and separating them by a goodly amount so that the linkset is on my land. I thought I'd put a car there too. As if someone parked there and got booted. That's where I had this LI jump problem. 

Again, thanks so so much for your responses. I'm making a NC of your responses so I can refer to your expertise in the future.

To be honest, the original car, when linked, went all screwy. Wheels at angles, etc. But it's LI DID go down. Before I had seen your replies, I went with another car that didn't exhibit any of these visual problems nor did it's linkset LI go astronomical.

Here's a pic of what I ended up with. For reference, my land here ends at the wall on the right. The land from the wall to the road is the Atoll Road.

Edited November 7, 2021 by Egon Rothschild