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eMagin Z800 Review

June 7th, 2007
by Sébastien Kuntz
Copyrights © 2007, VResources
All Rights Reserved


Image courtessy of eMagin Corporation (http://3dvisor.com)

Introduction

I could finally get my hands on an eMagin Z800! I've been using it for some time now, and I'm finishing writing the building blocks for the Virtools VR Library, so here's a in-depth review of this HMD, oriented for pros.

Out of the box

The bag in which everything is delivered is pretty slick and convenient. It holds the HMD, a small VGA/VGA cable, a small jack cable, a wiper/tissue, and the CD with the drivers.

Installation

The physical installation is pretty straightforward. The provided instructions are easy to follow and there are only a few cables to connect to get started.

Then, if you only have a GeForce, you have to install the nVidia consumer stereo drivers.

You should just configure them so that the stereo resolution is 800x600 at 60hz. It is all well explained in the documentation. The eMagin drivers are easy to install, and you should be able to move your mouse with your head in no time

If you have a Quadro, the native stereo drivers should be good. We've began testing with an ATI FireGL card, but it wasn't working. I'll update the article if we manage to.

Displays

The two 800x600 OLED screens are very sharp. Brightness can be modified at runtime by a button on the control box. I find the original colours a bit pale, but you can tweak them with the nvidia control panel. The black levels could be better (linked to contrast ratio), even at the lowest brightness. Once adjusted all pixels are in focus and the vision is very comfortable. At first the field of view is a bit tight, but once you're in your application/game you forget about it. There is some noise in clear colours which is a bit disturbing if you're having a static, bright background, which I had for some composition I tried. It seems to disappear completely in dark colours.

The stereo effect is really nice and is very easy to use with the nVidia 3d stereo drivers. It also works with the nVidia Quadro stereo (I'm still having some problem on my Dell laptop, but it seems to be only on mine.)

The optics are very tolerant regarding your eye position which is nice to keep the immersion, and makes the position calibration procedure shorter.

Ergonomics

The HMD is lightweight thus comfortable to use and it doesn't move once in place. The head strap was starting to itch my forefront after 10mins of use because I had tightened it to much. After loosening it, it was much better.

At first, I thought the fact that the world isn't occluded would prevent a good immersion, but once you're focused on your experience, you don't notice it. But as demonstrated in the Verdun application, hiding the real world is much more immersive!
The displays can be moved to adjust to your eyes. If the displays are blurred, they're probably not at the right place.

You can flip the visor module which contains the displays up to get back to the real world, without removing all the HMD. When putting them back you don't have to readjust everything, that's really a nice thing. On some HMDs the displays wouldn't stick in the upper position which is annoying when you're used to it.

Trackers

The tracker used in the Z800 is a Nec-Tokin 3D motion sensor.

The website states:

"NEC Tokin's 3D motion sensor is a system combining an accelerometer and magnetic sensor with a NEC Tokin Ceramic Gyro"

The orientation trackers have a very reasonable latency but they drift a lot. We've been using several Z800 at Laval Virtual, and after two minutes of use the roll and mostly the pitch were whacky. We had to have the user stand straight and recalibrate every couple of minutes, which seemed to be the norm for everyone on the tradeshow using a Z800.

The fact that we were using the raw data from the driver, not the mouse emulation didn't seem to improve the issue.

The yaw also drifts, but if you use the compass information instead of the raw yaw data, it seems much, much better!

We have tried to correct the drift by using the accelerometers data to compute the pitch and roll, but the accelerometers seemed to drift too. Moreover it seems they had to be calibrated too..

The tracker features webpage is very optimistic about the performances of their tracker, so if anybody wants to explain to me the difference with real world data, feel free!

(notice the advertised 125hz refresh rate where I could only get 50hz, see "SDK" below. Maybe by using directly the Nec-Tokin SDK we can get better results?)

Image courtessy of Nec-Tokin Corporation (http://www.nec-tokin.com)

We didn't use the accelerometers to get positional information. I'm not sure this is a viable solution anyway, I guess this would be more useful for basic gesture recognition (as proposed in their SDK), or to recalibrate the orientation data.

As for the mouse emulation, I tried the default tracker settings with Quake 3, and after only 1 minute the camera heading had already drifted by 180° ! Why don't they use the compass information which seems to give absolute values?

I'd also like that the doc gave some tips about how to configure the tracker settings to have the most comfortable experience? The virtual field of view matching the real one is one factor of realism. The precision of movement is another important factor. If your head turns by 90°, your eyes should show you what is at 90°, otherwise you'll start to experience some simulator sickness. After 3 mins in Quake 3 I had to remove the HMD or I'd throw up on my shiny new keyboard.

SDK and Support

On the plus side, the SDK is really well done, extensively documented with good examples, and last but not least, you have all the source code! The SDK as a whole is of high, professional quality, and I'm quite impressed by it (unlike some other much more expensive tracking devices that I won't cite here...). You have access to both low level and high level C++ classes and their equivalent C functions. C# and .Net bindings are also available.

Low level functions give you access to raw data. High level functions will create a thread to get the data for you so that you don't have to poll or create a thread yourself. That's nice since I don't like to work with threads. It will call callbacks when new data is available, and do some basic gesture recognition.

On the negative side, I would have liked more in-depth explanations on the trackers, what you can expect of them, tips on how to use them, units of the data etc (I read the nec-tokin webpage only later).

The SDK is supposed to support more than one HMD on a PC, but that's not yet the case. You can only get the data from the first HMD.

Note: you *absolutely* have to close the visor utility otherwise your application won't run and you'll have to reboot your computer!

Note2: the default thread period is 100ms, so you might want to set it to the minimum allowed which is 30ms and gives a smoother movement. The strange thing is that if you manually poll the data, you can get down to 20ms. I've hacked their code so that the thread period is 20ms, which is much better!

The support is not very responsive, even when you say you come from a big company for an urgent and important event. (Maybe I should have tried their toll free phone number. Would I have had a direct access to a developer?) Their answers could be more precise, and they elude some questions, but it's generally helpful.

Note3: At first I wasn't able to have the OS recognize the HMD as an external monitor. For that, you have to run the visor utility, *uncheck* the "External Monitor" box, and then it works.

Conclusion

Generally speaking this is a good HMD. This was the most widely used HMD at Laval Virtual 2007 and apart from the tracking drift, people seemed to be happy with it (most of them used the mouse emulation). I have tried a very impressive application where I really felt immersed there, so it all depends on how you use it.

The displays are bright and sharp, the optics are really comfortable. The colours could be better. The HMD is comfortable to use and position correctly.

The big problem is the tracker drift. If only they managed to correct this it would be really a great HMD.

At $1,499 USD, it's not affordable for gamers anymore. But for VR labs, students and other professionals, it's still very cheap and comfortable to use compared to the majority of other HMD.

Our final verdict

Based on what we could see from this unit, it is well worth buying it. We recommend it to anyone looking for an affordable HMD device which displays quite respectable performances.

Some criteria like the durability and pricing are estimates or based on information as it was available at the moment of this writing on the manufacturer's web site. You can consult their web site for up to date information at:

http://3dvisor.com

About the criteria used:

  • Aesthetics: measures our general impression on the device aesthetical look and ergonomics design. Controls user friendliness and accessibility is an example of factors we evaluate.
  • Robustness: measures our general impression on the device mechanical assembly quality.
  • Durability: measures our general impression on the device expected durability. This is only an estimation based on visible and observable physical and mechanical assembly characteristics of the device. The warranty provided by the manufacturer is also considered on our final rank decision.
  • Performances: measures our general impression on the device performances based on the benchmark result we got during the evaluation.
  • Pricing: measures our general impression regarding the pricing of the device.

About our ranking system:

0

Not acceptable - totally fails this criteria

1

Not acceptable - fails most aspects of this criteria

2

Not acceptable - fails many aspects of this criteria

3

Not acceptable - fails some aspects of this criteria

4

Not acceptable - some adjustments required to meet this criteria.

5

Barely acceptable

6

Average

7

Good - needs improvements on certain specific areas.

8

Very good

9

Excellent - very minor problems noted.

10

Perfect

The content of this review is copyrighted by VResources and its authors. No reproduction, in part or in its totality, of the present article is allowed. Please contact the authors for any inquiry or comments about this article. Copyright 2007 - VResources, All Rights Reserved.

Visor flipping issue

We noticed the same issue with our unit. The metal junction linking the visor module to the head straps part is very thin and weak. Even if it sounds robust enough, it seems like they did not put enough friction on the screws so that the visor weight will cause it to flip back down. We did not try to tighten screws but it might be a solution if they made it adjustable to some degree.

Even with these few problems, the Z800 HMD remains one of the best HMD on the market in its price range.

Linux drivers

And for those users looking for Linux drivers for the Z800, I've just released a new alpha headtracking kernel module to go along with the existing z800 kernel module. For more info about them, see here: http://antimass.org/z800 . Cheers, Adam

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