Temporary on Rez
Objects set to "temporary on
rez" (temp-on-rez) automatically die without triggering any
events after a short time and do not count against the
prim allotment for the
land parcel beneath them. Otherwise, they're the same as an ordinary prim: visible to all, able to be scripted, interacted with, etc. Temp-on-rez objects do not make
assets when they are deleted, so the deletion events are not a load on the asset
server.
An object's temporary on rez property can be set with
llSetPrimitiveParams, or by checking the "Temporary" checkbox in the building editor in the SL client.
llGetPrimitiveParams can be used to determine if an object has been set to temporary on rez.
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Always use temp-on-rez when rezzing a large number of "disposable" objects such as bullets or other projectiles. Doing this allows them to automatically be cleaned up, should they break or encounter no-script land. This is both good scripting practice, as well as good for your sim and neighbours. It also keeps you and your customers happy by not getting complaints sent after them.
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Temp-on-rez prim limits
According to Andrew Linden, as of
SL 1.11, there is a limit on the number of temp-on-rez prims allowed on a parcel based on the parcel's prim limit.
The formula is currently "
temp_prim_limit = 0.5 * regular_prim_limit + 20", or
500 temp-on-rez prims, whichever is
smaller. Any rezzing above this limit will cause older temp-on-rez objects to immediately be garbage collected until the limit is reached again. As the aforementioned forum thread indicates, the limit may be tweaked in later versions.
Lifespan of Temporary Prims
According to Andrew Linden, the current system is a per-frame (1/45th of a second) tally correction for any parcel that has gained or lost objects. If the parcel is over its temp-on-rez limit, it aggresively deletes older temporary objects until it is within its limit. Otherwise, if it has any temporary objects at all, that parcel is scanned for old ( > 60 seconds) temporary objects every 10 seconds.
In practical terms, expect the lifespan of temp-on-rez objects to range
between 60 and 70 seconds.
Observations
WARNING! The following behaviour was observed in 1.12.0 (2006-08-23). Creating an object and then setting the "temporary on rez" property DOES make the object temporary (eligible for garbage collection) directly, even without being taken and re-rezzed. Setting the "temporary on rez" property on an existing object DOES decrease the number of objects the simulator thinks are on the parcel.
Taking an object with the "temporary on rez" property set into inventory and rezzing it gives a copy of the object which is temporary, and which does not count towards the number of objects the simulator thinks are on the parcel. This is the normal case.
If you remove the "temporary on rez" property from an already-rezzed temporary object, that object will no longer be temporary and will not be garbage collected. However, it will then count against the number of objects on the parcel.
Although rezzing a new non-temp-on-rez object on a parcel isn't allowed if it would take you over the parcel limit, it does appear to be possible to remove the "temporary on rez" property from a temporary object sitting on a full parcel. This puts you in a situation where the "About Land" dialog says something like "235 out of 234 (1 will be deleted)" and a little while later said prim will be removed after all. Note that such an object is not deleted outright as a dying temp-on-rez object would be, but is sent back to your "Lost and Found" folder instead.
Primitive |
Object |
Rez