[osg-users] Anyone Experimenting with OSVR

[Jan Ciger]

On Mon, Nov 9, 2015 at 11:26 PM, David Glenn <david at dglenn.com> wrote:
> Greetings All!
>
> Is anyone experimenting with OSVR yet?
>
> I know that there is some Oculus stuff that people have tried with some limited success, but just wondering if anyone looked at it from the OSVR standpoint!

I am doing quite a bit of OSVR integration work at my current job,
mostly because we use GearVR quite a bit and getting VRPN working on
Android and in Unity3D is a pain. It can be done, but OSVR had
supposedly supported Android port and more features, so we have tried
that instead.

In short, the framework parts related to device management and
tracking work, even though you need to expect some rough edges. It is
basically a layer on top of VRPN (the VRPN maintainer now works for
Sensics, the company behind OSVR), with the protocol mostly being
compatible. For example, you can use VRPN clients to receive data from
an OSVR server for devices like trackers or buttons, of course without
the extra metadata.

I have also written a few plugins for OSVR to expose data from other
sources (Kinect, Natural Point's Optitrack, etc.) or to
process/transform tracking data using scripts - the APIs required are
there and it basically works, even though a few things are still a bit
rough. It is usable, though.

Where things could go south is if you try to do things the OSVR
developers didn't anticipate - I think I am one of the leading
external bug reporters on their issue tracker because we are always
finding use cases they didn't expect or that nobody has attempted
before.

For example, right now it is impossible to use an external OSVR server
(i.e. not running on the same machine as your client - probably the
most common VRPN setup) with the official code, unless you use kludges
like defining an environment variable or a local OSVR server to point
to the remote one. The code to allow this is there and works, but I
was told that the clients are not supposed to use the sw in this way
so it is not exposed in the API. I have a patch submitted for this,
but it wasn't accepted yet.

I cannot comment on the parts related to HMDs (management of
distortion and such) - never used it and Oculus Rift and GearVR that
we use pretty much require the use of their native SDKs so unless you
have the OSVR HDK helmet, it is probably not going to be all that
useful, because the Rift-proprietary features will not be supported
(at least with the current code - could change in the future).

>From what I can see from the source, the HMD support is right now
mostly about publishing the HMD parameters (like the distortion
parameters, focal length, etc.) in the metadata tree and then there
are some utilities and examples provided that can use that information
and calculate the correct matrices for your client application (it
uses Eigen everywhere, so it is API agnostic), making it independent
from the exact model of the HMD you use. At least that's the idea, the
practical implementation (and performance) of this remains to be seen.
There may be some other tools available which are outside of the main
OSVR-Core tree, but I haven't looked at this part of OSVR in any
depth, so take this with a grain of salt.

Also keep in mind that OSVR is still under a heavy development - if
you need unconditional API/protocol stability, it is probably safer to
use VRPN, which is a known quantity and pretty much an industry
standard. In addition, there is likely a lot of OSVR development
happening out of public view - they (Sensics) are certainly at least
in talks with major hw/sw players if not in collaborations already,
judging from the list of partners, so things will most likely change
quite a bit.

On the other hand, VRPN is very limited compared to what OSVR can do,
especially when it comes to publishing of the metadata - publishing
things like names of the tracked rigid bodies, marker - rigid body
associations, orphan markers in the scene, quality of tracking per
joint, etc. VRPN cannot deal with any of that without major
nonstandard kludges. OSVR is also designed for runtime reconfiguration
without restarting the server, so you can have plugins publish changes
(e.g. when a new device is connected) on the fly and the client will
pick that up and re-establish the data routing correctly. Again not
something typical VRPN setups can do.

I suggest you test the software and see whether it fits your needs.

Regards,

Jan