Difference between Prims and Land Impact

[Candy Tangerine]

Hi, I've always wondered, what is the difference between the prim count and the land impact?  I have a sofa that is 21 prims but 14 land impact.  What is it that creates that difference?  Thanks.

[Rolig Loon]

In a nutshell, Land Impact is all that counts.   It determines how hard the servers have to work to create, rez, display, save your objects.   PrimCount is just that, the number of prims in your object.  It's part of the total picture of Land Impact, but doesn't take into account scripts, physics, materials, and other factors that add to the total server load.  For most practical purposes, you can pretend that you didn't see that number.

[Chic Aeon]

Prim count equals "pieces" of an object.   A table could be ONE prim if made of mesh and the creator joined all the parts together before exporting.  The same table (in looks) could be five prims if the creator exported the table top and the leg and then used four legs.   As Rolig says "prims" don't really count these days. But it is good to note that many of us oldtimers still say "prim" when we actually MEAN "land impact".  Even those of us who have been making mesh for seven years or so LOL.   So sometimes you need to translate what has been said or written. 

[ChinRey]

To add the historic perspective, back in the early days when prims were the only building material, LL decided to keep the load calculation simple and jsut count the number of prims. That became a bit tricky when sculpts were introduced though since sculpts are quite a bit heavier on the servers and bandwidth than most prims but they decided to keep the system as it was at that time. However, when they introduced mesh in 2011, they had to do something because a mesh can be anything from light as a feather to ultra heavy. So they introduced a more elaborate land impact calculation.

The problem with this was that some older builds were so heavy they would break with the new system so they decided to do some double accounting: a build that only uses building materials and features that existed before LI was introduced is still calculated the old way, any build that uses materials and/or features that was introduced later, is calculaed the new way.

[Candy Tangerine]

Thank you so much Rolig, Chic, and Chin.  That explained it perfectly to me 😀