[RossBencina]

I'm not familiar with the SteamVR tracking modules that you linked, however from the link:

> The CM1 contains all the circuitry necessary to convert SteamVR Tracking base station infrared light into a digital output that encodes the angle of the sensor from the base station.

That implies that it's not a full location tracking solution by itself (angle only). The data sheet[0] doesn't seem to shed any further (ahem) light. Maybe I'm wrong. And I'm certainly interested in learning more. Do you have more details on the SteamVR tracking system?

[0] https://www.triadsemi.com/download/16501/

[RobertLong]

Correct, it's only going to give you a signal "upon incident light from an IR source once the threshold level for light intensity has been exceeded"[0].

What you are getting in this chip is all of the work Valve and Triad have done in improving the accuracy of that envelope signal. Essentially, the accuracy in the timing of that signal == the accuracy of the position. There's a really good talk from Steam Dev Days[1] (that I was fortunate enough to attend) that gives a good overview of all the work that has gone into SteamVR tracking.

[0] https://www.triadsemi.com/download/16617/

[1] https://www.youtube.com/watch?v=m3wKLZHH_dM

[ashtuchkin]

The cool thing is you can probably just use Teensy and my code to convert the envelope to 3d position. I haven't thought about that :)

[moron4hire]

Apparently the math is complex (and proprietary). They claim they saturate a single core of an i5 processor with all of the math converting the timing signals for all of the devices to position. With the official kit, you don't do anything on the hardware side on your own with regards to figuring out position.

[RobertLong]

Wow, definitely post more info on this if you can. I had no idea about this. I want to take the class, but can't shell out $3000 for a side project.

[moron4hire]

I was previously under the impression that the photodiodes figured out their own angular position and you received a library to convert those values into a single rectilinear position and orientation on the device. This is not the case. The photodiode ASICs basically just convert photons to voltage and clean up the signal. The official kit includes an FPGA to pack up all the sensor data and an MCU to give you an SPI interface to that data. The system is pretty much end-to-end, you mostly just get a chance to inject your own data about button clicks or what have you into the data stream from the device. SteamVR on the PC does the work of making sense of the data.

There is a huge amount of design that has to go into the sensor layout. Bad sensor layout will cause significant problems in tracking. It's extremely constraining in what you can do.

The system is designed to work with one base station. The second is only for redundancy, covering areas of the play area that are occluded for the master base station by your own body.

In contrast, Oculus uses cameras to detect IR LEDs on the device. It's kind of inside out from SteamVR. They have to them do image processing on the PC to get the angular position with regards to the camera of each LED. SteamVR just has to convert timing values into laser emitter motor positions. Once you get to that point, they are pretty much the same, having to compute position and orientation from that data. It's just a lot cheaper for SteamVR to acquire that data.

It also means that adding more cameras to Oculus adds to the workload, whereas adding base stations to SteamVR does nothing to the PC. Both will increase workload to add more devices, but it's negligible compared to the image processing Oculus has to do. Oculus' system is fundamentally unscalable. SteamVR is fundamentally scalable.

[moron4hire]

We've officially been told that the SteamVR information is not confidential. There is a lot, so if you have any questions, find my email in my profile and just send me a message.

[RossBencina]

Thanks that video is really good, watching now.

@ashtuchkin maybe link it from your page?