[Opensim-dev] Standardizing types in OpenSim

[Hurliman, John]

Hello list,

This is my first e-mail to opensim-dev so I'll start with an
introduction. I'm an engineer at Intel researching scalable models for
virtual worlds. A lot of the research will revolve around open,
user-generated content models like Second Life and OpenSim. I'm also the
primary developer of libOpenMetaverse (formerly libsecondlife, still
located at http://www.libsecondlife.org/ for the time being).

I've spent some time looking at the lower level components of OpenSim
and have a patch to propose. The basic type objects (vector, quaternion,
rays, etc) are spread out and duplicated over several internal classes
and external libraries. There are at least five different types of
Vector3, multiple quaternion and matrix classes, etc. Some of these are
classes instead of structs, meaning a basic operation like subtracting
two vectors and putting the result in a third creates several new
objects on the heap that the garbage collector has to track. I believe
this is responsible for a lot of the heavy memory and garbage collector
activity I am seeing. There is also a lot of duplicated code which has
led to incorrect constructors (such as new Vector3(x, y, y)) and makes
things more difficult to unit test.

The OpenMetaverse library has a set of types useful to virtual worlds
that have been in development for two years and implement all of the
functionality needed in OpenSim. I've created a very large patch that
upgrades OpenSim from libsecondlife to the latest libOpenMetaverse,
drops Axiom, and uses the built-in libomv types wherever possible. There
are a few places that I have skipped over for now to avoid introducing
too many moving parts in a single patch: BulletX still uses Mono.Xna,
and Meshmerizer still uses PhysicsVector/Vertex/Triangle.

I've spoken with some of the OpenSim developers about problems keeping
up with libsecondlife changes. The major changes happened to prevent a
trademark conflict with Linden Lab, and also establish libopenmv as a
generalized platform for building virtual worlds instead of a library to
connect to Linden Lab's servers. I think this patch is an important move
in that direction, and to prevent any future headaches I'm volunteering
to maintain the OpenSim->libOpenMetaverse dependency in the event of any
API changes.

I'm working on grid mode compatibility testing (sandbox mode appears to
work fine) and will have the patch on Mantis early to mid next week. So
far the patch itself weighs in around 1.7MB plus binaries. Twenty
revisions have passed since I initially wrote it and maintaining it
against the latest SVN can be time consuming, so I wanted to kick start
with this e-mail before posting the patch.

John Hurliman