[sldev] Re: A patch to allow creation of megaprims from within the viewer

[Dale Mahalko]

As I understand it, primitives around the edge of a sim are supposed
to be treated as if they are objects in a neighboring sim.

Over and above the 15,000 prim limit per sim, each sim is also
supposed to include prims from neighboring sims which overhang into
its territory.

It is possible for a sim to include up to a maximum of 75,000 prims if
it is unfortunate enough to be surrounded by four sims which all have
their 15,000 prims overhanging into the center sim, plus also its own
15,000 prims.


To limit the amount of prim sharing between sims, they only overlap
"into" the adjoining sim's territory by 5 meters, which should in most
cases hopefully reduce the total number of prims shadowed across the
border between sims. It also means that only prims up to a radius of 5
meters can be permitted if there is to be a consistent user
experience.

If prims over 5 meter radius are permitted, it cause these oversize
prims near the edge of the sim seem to go "missing" from the physics
of the neighbor. A 20x20x20 cube that is 9.5 meters from the neighbor
is not processed as a physical object in the neighbor sim because it
is more than 5 meters from the sim border. But it visually seems to
overhang 10.5 meters into the neighbor sim. It seems the prim could be
walked through in the neighbor sim but not in the actual sim where it
is actually located.


If megaprims are to be permitted as part of the world experience, then
the "cross-sim prim shadowing" would also need to be increased so that
very large prims overhanging into a neighbor sim are counted in that
neighbor's physics processing.


That is the theory anyway. I have not tested it for validity.

I do not know if corner sims around a mainland sim count in the prim
sharing. (I assume they do since this shadowed border overhangs a 5x5
meter region in each of the four corner sims.) If corner sims are
included in the shadowing, then it is possible to further overload the
above mentioned sim to 135,000 prims, by putting all 15,000 prims of
each of the eight border sims sims within the 5 m border of the center
sim.

- Scalar Tardis / Dale Mahalko


On Wed, May 14, 2008 at 8:42 PM, Able Whitman <able.whitman at gmail.com> wrote:
> Actually, I'd be interested to know more about the historic underpinnings of
> the 10m limit. I've done some searching, but I haven't found any information
> about the original motivations behind it.