Thursday, January 5, 2012

A New Way to Count Prims

Erratum

I received an instant message from Ample Clarity, the creator of the one-prim piano I blogged about night-before last.

Ample thanked me for mentioning the piano and let me know the piano isn't mesh after all-- it's a well-done scultped prim.

So maybe complex one-prim mesh objects have a high cost after all. I don't have enough data to know.




Written 4 January, 2012

A New Way to Count Prims

I'm not sure how I missed it, but with the advent of mesh content in Second Life there's a new way to count prims on one's land: Prim Equivalents.

In short, this means there's no longer a 1:1 ratio for prims/prim count. Some prims (and specifically mesh) now count for more than one.

The best explanation I've found is Jenni Darkwatch's, which can be found here. However, I'll do my best to explain.

Until now, a prim was a prim. Although some prims (notably the cube) were easy to render and others (notably the torus) were complex and hard to render, although some prims contained scripts and some didn't, although some were big and some were small, each prim counted as one toward the limit on one's land.

With mesh, that has changed. Some prims count more than others.

The prim equivalency of a mesh object is calculated by a formula I won't go into here (you can follow the link; Jenni explains it), but it has to do with size and complexity.

What this means is a seven-prim mesh object on your land may count as seven prims or it may count for considerably more.

As a test, I rezzed the free boat the Lindens have been giving away to paid subscribers. I couldn't see it when I first got it, but since the newest iteration of Phoenix has mesh support, it now looks like a sailboat instead of a huge cube.


The boat consists of 13 mesh prims, but it counts as 62 prims toward the parcel and sim allotments.Ouchie!

Does This Say 147 Prims Equivalents? Yes It Does!
The Sailboat Usually Shows as 64 Prim Equivalents
Methinks There's a Server Bug Afoot! 
Depending upon the skill of the mesh creator, complex mesh objects can weight in at 1:1. Check this great mesh concert grand piano from 1 Prim:


Last night I bought it to replace the beautiful prim sculpt-and-prim Musical Alchemy piano at our PG Den of Iniquity. The mesh piano consists of one prim and counts as just one prim on the land.

Note the raised black keys:


Here's the Musical Alchemy grand:



Now, the mesh piano doesn't look quite as good as Musical Alchemy's, and it has fewer features, but considering Musical Alchemy's grand piano is 85 prims and the black keys are another 23, I was more than willing to sacrifice a little quality to gain 107 prims!

When we have concerts on Whimsy I'll rez the Musical Alchemy grand, but for day-to-day, the mesh piano will more than suffice.

The edit tools to deal with prim equivalents are not to be found in V.1-based viewers, but are in Viewer 3. I suspect Firestorm has them, or will soon. Phoenix doesn't have them, but it shows prim equivalents in parentheses to the right of the prim count, as in the screen shot above. That;s handy, as it lets you see how heavily mesh objects impact your land. Without that feature, it would be necessary to see how many free prims you have, rez the object, re-check for free prims, and use the magic of subtraction.

The practical application of this post so far is: watch out-- a prim is no longer a prim-- but there's more!

For objects made of prims (and, I believe, sculpts), you can count prims as before-- but if a single prim in a linked set is mesh, the entire object will count under the new system.

Prims with simple shapes like cubes have a low prim equivalency, but according to Jenni, torii, which are complex count for 37 prims. that means a box of 12 single-prim donuts in a one-prim mesh box would consume 445 prims! Ouchie!

Viewer 3 contains tools for dealing with prim equivalents-- specifically, a counter and a box that allows physics type to be set:

Photo From Jenni Darkwatch's Article
With these you can assign regular prims and linksets made of regular prims so they are counted as prim equivalents. This can lead to the above-mentioned donut effect, so if might be wide to do your experimenting at a sandbox.

Oh-- according to Jenni, a single script will DOUBLE a prim or mesh linkset-s prim equivalent! So doubly beware!

I can already see it will be possible to game the system-- for instance, link sets of prim cubes will count as just one object if the physics type is set just so.

I can appreciate the need for some sort of accounting system to deal with the new mesh content, and maybe prim equivalents will work for the great good-- but there are problems-- specifically counting torii and other complex prims with high equivalency just because a mesh prim is included-- and doubling the weight because of a single script? Is this the ghost of script limits past!

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