November 01, 2008

The truth about temporary prims - a fun experiment

In the recent discussion about OpenSpace/Void sims, one argument heard often is that people abuse these kind of sims with so-called "temprezzers". There are several extra attributes a prim can have:
  • Physical: the prim gets affected by gravity and impacts with other prims
  • Phantom: the prim can be permeated by other prims abd avatars
  • Temporary: the prim will get deleted without trace after a short while
Temporary prims do get counted on the parcels primcount, but do not get limited by the parcels prim limit. So if a parcel has a prim capacity of 400 prims, you can still have temporary prims exceeding this limit.

The main intended use for temporary prims is to have an object rez props that are only needed for a short time. Many of you have seen palmtrees where every now and then a coconut falls out. The coconut is usually a temporary (and physical) prim, so it vanishes by itself after a short time without littering the parcel and without the need to manually clear it up. Another use for temporary prims are projectiles from weapons like arrows or bullets - again not caring about the parcels prim allotment and not needing to clean up are the main reasons.

However due do the tight prim economy, a second use for temporary prims was found, the so called "temprezzers". A temprezzer consists of a 1-prim base of a regular prim, and then rezzes a complex object (a tree, a yacuzi, a boat - you name it) as a temporary object. As soon as this object gets cleaned up by the simulaor, the temprezzer rezzes a new instance of it. With a temprezzer it is easy to rez way more objects than the parcel prim allotment would otherwise allow.

Now where do these extram prims come from? A full sim has a prim limit of 15000 prims, an OpenSpace/Void sim has a prim limit of 3750 prims. My understanding so far was that a temprezzer "loans" (other people say "steals") free prims from the sim's prim allotment. So if the sim has 14000 of the 15000 prims used, a temprezzer could use a maximum of 1000 prims until it meets the hard limit of the sim's prim allotment.
SL artist and blogger Raul Crimson has a different opinion. He claims that there is an unlimited amount of temporary prims (very much like there is an unlimited amount of prims avatars can have attached to themselves regardless how full the sim is), and that this is one of the problems encountered with OpenSpace abuse.

Time for a test, it seems. Together with Ivanova we logged into the Beta Grid and found an empty sandbox with 15000 prims available. The next question was how to rez 15000 prims. Ivanova experimented a bit with self replicating prims, and we were discussing how a "kill switch" could be implemented since 150000 channel listeners would probably lag a sim down to a halt. Recursive rezzing however proved to be quite mind boggling, and while she still had her head in the script, I started to rez and duplicate cubes. It turned out that by always doubling rezzed cubes, fairly quickly I was able to have piles of 2048 prims so the prim allotment could be used quickly.

Finally we had 14999 prims rezzed and therefore only 1 prim available. The last remaining prim we turned temporary, and then there were two options:
  1. We would not be able to duplicate a second temporary prim (the 15001 on the sim), thus proving me right and Raul wrong.
  2. We would be able to rez more than 15000 prims using temporary prims, thus proving Raul right.
With some suspense, I selected Edit on the temporary prim, and shift-dragged it in order to produce a copy. And to my huge surprise, I was able to make a copy thus having effectively 15001 prims on the sim.
However what was strange is that I could not shift-drag two temporary prims in order to go to 15003 prims. I could make many many surplus prims by shift-dragging a single temporary prim, but I was not able to create bulks of temporary prims. Further investigation would be needed how this affects temprezzers. But fact is: you can have more than 15000 prims on a full sim.

It is interesting to note that the 15000 prims produced quite some lag. Especially mass editing huge piles of prims slowed down operation significantly, not only getting the prims into edit mode, but especially moving and duplicating them. After Ivanova has left, I took on the task to clean up the sandbox (I did not want to have 15000 prims returned to my Lost+Found). So I thought it would be a neat idea to turn them physical (and temporary).

The effect was kind of neat, the piles collapsing in slow motion like in a Matrix movie, with cubes even get propelled away in slo-mo, however the lag was pretty severe. Still, it was fun.

I was pretty surprised that you can in fact exceed a sim's prim allotment with temporary prims. While I considered temprezzers up to now - dependng on their use - as unfair to the sim neighbours as it "steals" their prims, I can see now that they might even pose a real problem by exceeding simulator limits multiple times. However, further investigation is needed. Still the experiment was a lot of fun.
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