[sldev] Physical Object Prim Limitation

Soft soft at lindenlab.com
Wed Jul 30 21:15:50 PDT 2008


On Wed, Jul 30, 2008 at 10:57 PM, Thordain Curtis <thordain at thordain.com> wrote:
> As anyone who's tried to develop a vehicle well knows, the 32 prim limit (31
> prim if you're planning on letting somebody sit on it) limitation for
> physical objects can be a bit of an irritation.  The limit is hit pretty
> quickly when trying to create anything that actually looks compelling and
> realistic.  Vehicles supporting more than one passenger are left w/ an even
> smaller prim limit.  Add in particle emitters for special effects and you
> run out of prims _really_ fast.
>
> The 32 prim limit is a good thing, IMHO.  Nobody wants physical objects
> floating around their sim composed of 256 cut tori colliding with things all
> the time (Well, I can't think of anyone who would want that, anyways).  The
> limit is an effective limitation on how much havok (pun intended) a single
> object can inflict upon a simulator.  That still leaves people trying to
> create compelling physical content in an undesirable position.
>
> An interesting solution would be to allow all linksets to become physical,
> but only use the first 32 prims as the actual collision model.  The designer
> will generally be able to flesh out the basic shape of the object in 32
> prims or less....everything else is usually just decoration.  Add in a
> function like llSetObjectCollisionPrimCount() and physical objects could
> have even _less_ impact on a sim when designed properly.  A car, for
> instance, could use the 4 wheels plus an arbitrary (invisible) box for the
> collision model, bringing the objects physical complexity down to a mere 5
> prims.  The designer now has up to 251 prims (depending on the amount of
> desired passengers) to add detail to their vehicle, and the simulator is
> even happier than it was before with a 32 prim car.
>
> This solution is also backwards compatible with all existsing physical link
> sets, and would require zero scripting changes.  Designers who wished to
> make their vehicles more collision "friendly" could do so, but all existing
> content should continue to work unmodified.
>
> Anybody have any thoughts on this?

That, or something like it sounds pretty cool. A lot of more
complicated vehicles come with part as an attachment the rider wears,
which accomplishes much the same thing, but in a more roundabout way.

It might also be useful if seated avatars worked as phantom objects as
well. This way vehicles wouldn't stop when too many people sit on
them. Given that avatars register as prims on the end of link sets, it
could ease implementation as well.

A good way to go forward would be to write up a JIRA proposing this
and to drum up votes. You might also try stopping by the havok office
hours if those are still running. There's a list of all the active
office hours in the wiki.


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