Hybrid hydra + Wiimote
In reading comments about the accuracy of the hydra, and inferring a few points from it's SDK, I came to an interesting thought.
Obviously, long-term it's impractical, but technically it could be built as a hybrid device...
But here's the basic thing; The hydra appears to use some kind of magnetic tracking. While precise, it can apparently do some strange things, like being (in the words of John Carmack) as much of 15 degrees out of alignment after certain kinds of motions. - it does not appear to have any tracking other than it's magnetic system.
The Wii Remote plus on the other hand (that's the upgraded version with a gyroscope built in) has a reasonably precise gyroscope, and an accelerometer, as well as an IR camera.
The gyroscope can track rotation pretty well, and the accelerometer, when used together with the gyroscope, can give a very rough estimate of which direction the controller is moving.
The accelerometer also does a reasonable job of calculating 2 axes of rotation relative to gravity.
However, the positional tracking of a wiimote is absolutely terrible, while the hydra's is better, but by all accounts seems to have unreliable rotational tracking. (I think you can see where I'm headed with this...)
A final note about the wii remote is that using a modified sensor bar design with 4 led clusters instead of Nintendo's standard 2, it's been demonstrated in the past that you can track the remote's position relatively well.
However, since the IR camera is on the front of the remote, and has a field of view of all of about 30 degrees, in most situations it's difficult to keep it pointed at the sensor bar. (Using multiple sensor bars is theoretically possible, but you'd have no way to tell them apart.)
So... Here's what I was thinking; Create a rig that would allow a wii remote to be strapped to a hydra controller.
The Wii remote would be able to calibrate the hydra simply by being able to tell the approximate orientation, and comparing this to that of the hydra to see which of the two reported positions is correct.
The gyroscope would in general produce more accurate rotation data than the hydra, but you can obviously fuse the results. The hydra data can then in turn help to keep the gyroscope calibrated.
On top of this, you can set up the IR camera to track an external IR marker, which gives additional position and orientation data should the remote be pointing in the right direction.
If it is, you can fuse it with the hydra's position as well as recalibrating the gyroscope.
If not, you rely on the hydra's position data by itself. (though obviously, you can use the accelerometer and gyroscope readings to sanity check the motions the hydra is reporting.)
Maybe this won't improve things much, but given what I've heard the hydra's issues are, it seems like it would actually help quite a bit.
(Before you ask though; if you're using the hydra to track head movements for some reason, don't bother adding a wii remote to it as well; the headset itself can already do most of the things a wii remote can, and it appears to be better at it for good measure.)
As a hack, it could produce hand-held controllers that are slightly unwieldy.
As a commercial product however, (assuming it works), it would be as simple as integrating a gyroscope and accelerometer into the existing hydra designs. (and, potentially, depending on how much it helps, an IR tracking camera too.)
If it does anything to improve accuracy then, implementing a more practical equivalent to it should be fairly trivial by manufacturing standards. (That's not to say anyone would actually make such a thing though...)
Obviously, long-term it's impractical, but technically it could be built as a hybrid device...
But here's the basic thing; The hydra appears to use some kind of magnetic tracking. While precise, it can apparently do some strange things, like being (in the words of John Carmack) as much of 15 degrees out of alignment after certain kinds of motions. - it does not appear to have any tracking other than it's magnetic system.
The Wii Remote plus on the other hand (that's the upgraded version with a gyroscope built in) has a reasonably precise gyroscope, and an accelerometer, as well as an IR camera.
The gyroscope can track rotation pretty well, and the accelerometer, when used together with the gyroscope, can give a very rough estimate of which direction the controller is moving.
The accelerometer also does a reasonable job of calculating 2 axes of rotation relative to gravity.
However, the positional tracking of a wiimote is absolutely terrible, while the hydra's is better, but by all accounts seems to have unreliable rotational tracking. (I think you can see where I'm headed with this...)
A final note about the wii remote is that using a modified sensor bar design with 4 led clusters instead of Nintendo's standard 2, it's been demonstrated in the past that you can track the remote's position relatively well.
However, since the IR camera is on the front of the remote, and has a field of view of all of about 30 degrees, in most situations it's difficult to keep it pointed at the sensor bar. (Using multiple sensor bars is theoretically possible, but you'd have no way to tell them apart.)
So... Here's what I was thinking; Create a rig that would allow a wii remote to be strapped to a hydra controller.
The Wii remote would be able to calibrate the hydra simply by being able to tell the approximate orientation, and comparing this to that of the hydra to see which of the two reported positions is correct.
The gyroscope would in general produce more accurate rotation data than the hydra, but you can obviously fuse the results. The hydra data can then in turn help to keep the gyroscope calibrated.
On top of this, you can set up the IR camera to track an external IR marker, which gives additional position and orientation data should the remote be pointing in the right direction.
If it is, you can fuse it with the hydra's position as well as recalibrating the gyroscope.
If not, you rely on the hydra's position data by itself. (though obviously, you can use the accelerometer and gyroscope readings to sanity check the motions the hydra is reporting.)
Maybe this won't improve things much, but given what I've heard the hydra's issues are, it seems like it would actually help quite a bit.
(Before you ask though; if you're using the hydra to track head movements for some reason, don't bother adding a wii remote to it as well; the headset itself can already do most of the things a wii remote can, and it appears to be better at it for good measure.)
As a hack, it could produce hand-held controllers that are slightly unwieldy.
As a commercial product however, (assuming it works), it would be as simple as integrating a gyroscope and accelerometer into the existing hydra designs. (and, potentially, depending on how much it helps, an IR tracking camera too.)
If it does anything to improve accuracy then, implementing a more practical equivalent to it should be fairly trivial by manufacturing standards. (That's not to say anyone would actually make such a thing though...)