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Date:         Fri, 10 Mar 1995 19:26:25 PST
From: Roy_W_Latham@CUP.PORTAL.COM
Subject:      Comparing HMD's

> I read the August 94 Real Time Graphics Vol3 No.2 column titled "Head
> Mounted Display Survey - A Comprehensive Round-Up of Products" and am
> wondering why the price discrepancies for HMDs having similar (as
> stated)
> specifications. For examples:

>        1. Virtual Reality VR4 : $7900 with following specs:
>        - FOV: 36(V) x 48 (H) degree
>        - display format: 230x742
>        - overlap: 100%
>        - Display: Active matrix LCD
>        - Pixel Size (arc min): 8.1
>        - Pixel Structure: Triads
>        - weight: 33 ounces


>        2. VictorMaxx Technologies CyberMaxx ($699)
>        - FOV : 54x63 degree (wider)
>        - Display format: 250x480
>        - Overlap: 100%
>        - Display: Active matrix LCD
>        - Pixel Size: 7.75 (better)
>        - Pixel structure: Triads
>        - weight: 14 ounces (better)

> Anyone care to comment or am I missing something? I am especially
> interested in Virtual Research VR4 HMD as I'm using WorldToolKit
> software to develop application; but I believe WorldToolKit works with
> most HMDs as no software drivers are required - True? So, should I buy
> CyberMaxx? Please advise - anyone. Thanks.

> Albert Lim
> Nanyang Polytechnic
> email: jgfsegny@technet.sg


Which HMD you should buy depends, of course, on what your budget is and
what you intend to do with it. In a research environment, the Virtual
Reality VR4 is likely to be worth the extra cost, in my opinion. Beyond
the summary specs there are many issues, for example, the VR4 uses
 depixelization  technology.

Generally, there is no problem with software compatibility for head
mounted displays, but you have to be very careful about hardware
compatibility. Both the CyberMaxx and VR4 support NTSC inputs, but the
VR4 has a preferred RGB mode which is 480 x 640 30Hz interlaced. The
SPEA card sold by Sense8 supports the RGB mode, for example.

The main alternative to the VR4 is probably the Kaiser VIM. The VIM has
a larger field of view (which requires more pixels from your image
generator). Some people object to the way the multiple LCD panels are
mosaicked together in the VIM, though I didnUt have a problem with that.
When I saw the VIM a year ago, I thought it was too dim; the VR4 is
bright.

The resolution of any of the LCD-based HMDUs from any manufacturer is
really rather poor. However, there is a huge step in price to the
higher-res CRT-based displays. The CRT-based units start at around $45K
and you will often have to add another $20K for field sequential scan
converters.

Roy Latham
Editor, Real Time Graphics