===========================================================================
                                 I-GLASSES
  Dr. Peter Kittel                               peterk@combo.ganesha.com
===========================================================================

Perhaps some people already have heard about this new, fancy product.  
i-glasses!  by company Virtual I-O in Seattle are a new and affordable way
into 3d, or Cyberspace, if you want.  For Europe, we have set up a sister
company named Virtual Products, residing together with Amiga Technologies
under the same roof in Bensheim.

There are two parts: The main one are the glasses themselves, a color LCD
for every eye, independent ones.  Provided with the right signals, you will
see real 3D effects.  - The other part is called Head Tracker and is a
position (or better angular) detector for your head to enable real-time
looking around in space or do cursor-like movements by head movements.  -
Also mounted to the glasses are stereo headphones.

To provide the right signals for the glasses is nearly trivial.  They take
a fully standard composite video signal (one wire, plus two others for
stereo sound) as input.  Thus there are PAL and NTSC versions of the
glasses.  The NTSC versions already exist, the PAL versions are also now
shipping.  As the video signal is standard, it is always interlaced.  And
then the even lines (or one half field) go to the right LCD and the odd
lines (the other field) to the left (or the other way round, you can choose
with a switch a the set, so you don't have to worry during programming). 
This way of coding is also called "field sequential".

When I had the first PAL glasses in my hand and tried my first own
software, my experience was: You have to make the effect much more drastic
than I thought.  For the nearest point to the face I chose on a HiRes
screen 15 pixels horizontal spacing.  This is far too little I learnt: If a
pixel is infinitely far away, its two field pixels should be a quarter
screen apart horizontally, when the pixels gets nearer, the field pixels
get nearer to each other and cross finally.  Assume that the view angle is
only ca.  40 degrees.

Another hint for programming:
The resolution is rather low, something like 268 x 230 (don't have more
concrete figures, sorry).

The head tracker part is a bit more complicated, I'll quote below the data
provided to me by Virtual I-O.

>Date: Thu, 6 Jul 1995 01:58:14 -0700 (PDT)
>Subject: Head Tracker Specs

I tried to format the text the way it is in the developer's kit, but my
mail program created a mess of it.  The fax line has been busy, so
hopefully this e-mail will work. 

Contents

Introduction

Basic Tracker orientation
Communicating with the host computer Using the i-glasses! Tracker 
The i-glasses! Tracker command set
 Virtual i-O Tracker Modes
  Mode 0: Raw data mode
   Data packet format for mode 0 (Binary) 
   Data packet format for mode 0 (ASCII) 
   Send mode for data mode 0
  Mode 1: Cooked data mode 
   Data packet format for mode 1 (Binary)
   Data packet format for mode 1 (ASCII) 
   Send mode for data mode 1 Mode 2:
  Euler angles mode 
   Data packet format for mode 2 (Binary) 
   Data packet format for mode 2 (ASCII)
   Send mode for data mode 2 
  Emulation Modes
   Mode3: Microsoft mouse emulation mode 
   Mode 4: CyberMaxx emulation mode
  Examples 
   Modes for terminal debugging 
   Modes useful for applications
    Emulation modes 
     Mouse mode 
  Sample Code Notes:

Introduction The i-glasses!  Tracker, available exclusively from Virtual
i-0 Corporation, sends yaw, pitch, and roll information to a host computer.
This information is then available to application software for creating
immersive, head-tracking, real-time stereoscopic 3D simulations called
virtual reality.

Basic Tracker orientation

All orientation descriptions are from the perspective of someone actually
wearing the Tracker: Positive yaw is defined as a left head rotation.  
Positive pitch is an upward head tilt.  Positive roll is a left head tilt.

The coordinate system used is +Y up, +Z out, and +X right (The positive
axes can be formed with the right-hand index, middle finger, and thumb: a
right-handed coordinate system.  See Computer Graphics, principles and
practice, by Foley et al for more inf ormation on coordinate systems). 
creating immersive, head-tracking, real-t ime stereoscopic 3D simulations
called virtual reality.  Basic Tracker orientation All orientation
descriptions are from the perspective of someone actually wearing the
Tracker: Positive yaw is defined as a left head rotation.  Positive pitch
is an upward head tilt.  Positive roll is a left head tilt.  The coordinate
system used is +Y up, +Z out, and +X right (The positive axes can be formed
with the right-hand index, middle finger, and thumb: a right-handed
coordinate system.  See Computer Graphics, principles and practice, by
Foley et al for more inf ormation on coordinate systems). 

Communicating with the host computer The Tracker communicates with the host
computer via an RS-232C 3-wire serial interface (TXD, RXD, GND).  The
Tracker can run at 1200, 2400, 4800, 9600, and 19200 bps.  The Tracker can
be queried and tested using a standard ASCII terminal program.  All
commands are printable ASCII strings, and provide feedback to tell the
application if a command was successfully processed.  All commands (except
'S') begin with a '!' (Attention) and end with a carriage return (Hex D). 
The Tracker responds with an ' O' for OK or an 'E' for an Error.  The 'S'
(Send data) command requests the Tracker to send data to the host.  In this
case, only the requested data is returned, and a time-out check must be
used to determine if an error occurred.  Protected mode applications will
need a bi-modal serial handler.  A bi-modal serial handler for Watcom C/C++
is provided on the developer kit disk.  Using the i-glasses!  Tracker The
Tracker must be initialized to a known state before an application can
begin using the Tracker.  Since the Tracker may be in a continuous
streaming mode and at any of six supported bps rates, the host must send a
reset command until successful.  This will give the Tracker time to stop
sending data and to change its communications rate if necessary.  After the
Tracker has been successfully reset, the host must put the Tracker into the
appropriate mode for the application (polled, streaming, ASCII, bina ry,
etc.).  For emulation purposes, the Tracker retains its last operating
modes (data mode, send mode, and send format) when it was powered off.  All
applications that directly support the Tracker must set and verify the
operating modes on initial startu p. 

The i-glasses!  Tracker command set All commands to the Tracker are
printable ASCII characters.  Each command (except 'S') is terminated with a
carriage return (Hex D).  Result codes, 'O' and 'E' are ASCII 'O' and 'E'.
Tracker orientation data is sent to the host in either ASCII or binary. 

The serial protocol is one start bit, 8 data bits, no parity, and one stop
bit.  Command Description !R Resets the Tracker to the default state:
cooked, polled, binary mode.  All applications should put the Tracker into
Cooked, Euler, or an emulation mode before requesting orientation data.  !V
Get the Tracker revision string.  This allows future revisions of the
protocol to work as applications will know what version of the hardware
they are talking to.  The string format is: M<16 chars>P<16 chars>T<8
chars>Hxxx.xxxFxxx.xxx where M is for Manufacturer followed by a 16
character ID string, P is for Product code followed by a 16 character
product code or serial number, T defines product Type, H is for Hardware
revision followed by a C format "%07.3f" revision string, and F is for
Firmware revision with the same C format string.  An 'O' or an 'E' is
appended to the end of the returned string to indicate whether an internal
self test has passed or failed.  !M<data mode>,<send mode>,<send
format>[,<magnetic filter>,<tilt filter>][,<Mouse sensitivity>,<Mouse
threshold>]<CR> Tells the Tracker to change data mode, send mode, send
format, and filter modes, and is terminated with a carriage return (Hex D).
Data modes are '0'-'4'.  Send modes are 'P' for polled, 'C' for Continuous,
and '0'-'1' in mouse mode.  Send formats are 'A' for ASCII and 'B' for
Binary.  Filter ranges are '0' for none, and '7' for maximum.  These
parameters must be sent all at once, separated by commas, and in the
defined order.  Filter modes and mouse parameters are the only optional
commands and shouldn't be set by the application, but rather by the Tracker
manager software.  If they are set by the application, the user must be
able to change them.  If the optional mouse parameters are set, the filter
parameters must also be specified.  The mouse sensitivity and threshold
settings are fully described in the mouse emulation section.  Only Tracker
manager software should set mouse settings.  S Tells the Tracker to send a
packet of orientation data.  In continuous modes, 'S' starts the stream.
When a '!' is sent, the stream stops and the command is processed.  '!'
followed by a carriage return can be used to stop the stream. 

Virtual i-O Tracker Modes Mode 0: raw data mode The Tracker sends raw data
readings from the sensors.  The numeric format is 12 bits unsigned
(0..4095) stored in 16-bits for all values.  This mode is most useful for
debugging the hardware.  Data packet format for mode 0 (binary) The total
packet size is 12 bytes.  The byte format is:

   Byte    Description
   0  Header (always 255)
   1  X-axis high byte
   2  X-axis low byte
   3  Y-axis high byte
   4  Y-axis low byte
   5  Z-axis high byte
   6  Z-axis low byte
   7  Pitch high byte
   8  Pitch low byte
   9  Roll high byte
   10 Roll low byte
   11 Arithmetic checksum (Bytes 0-10 added together) 

Data packet format for mode 0 (ASCII) The data is transmitted in the
preceding form in ASCII hex with spaces separating each two byte ASCII hex
value.  This is for debugging only.  Send mode for data mode 0 The send
modes for data mode 0 are 'P' for Polled and 'C' for Continuous.  In
continuous mode, a '!'<CR> command stops the stream and the 'S' command
restarts it.  To read data in continuous mode, the application searches for
a start header (255).  Once f ound, the rest of the packet must be read in,
the checksum computed and compared to the packet's checksum.  If the
checksums don't match, the application must reread the data one byte beyond
where it last found a 255 and start the process over again.  Alternatively,
the application can stop the stream with a '!'<CR>, pause a few character
send times, flush its read buffers, then send an 'S' and begin reading the
stream.  All raw modes should not be used for commercial applications.
They are for factory debugging only. 

Mode 1: Cooked data mode The Tracker scales the magnetic vector, centering
it about the zero, and linearizes the tilt sensor readings based on
internal factory calibration constants.  This is the mode to use when
performing the angle computation on the host.  The data format is s igned
16-bit words.  The x, y, and z magnetometer readings are approximately +/-
16384 (This varies with the Earth's magnetic field).  The pitch and roll
readings are converted to linear values where +16384 = 180 degrees and
-16384 = - 180 degrees.  To convert to floating point: degrees =
(float)reading/16384.0*180.0.  A provided C library routine converts the
cooked data values into yaw, pitch, and roll. 

Data packet format for mode 1 (Binary) 
The total packet size is 12 bytes.  
The byte format is:
   Byte  Description
   0  Header (always 255)
   1  X-axis high byte
   2  X-axis low byte
   3  Y-axis high byte
   4  Y-axis low byte
   5  Z-axis high byte
   6  Z-axis low byte
   7  Pitch high byte
   8  Pitch low byte
   9  Roll high byte
   10 Roll low byte
   11 Arithmetic checksum (Bytes 0-10 added together) 
Data packet format for mode 1 (ASCII) 

The data is transmitted in the preceding form in ASCII hex with spaces
separating each two byte ASCII hex value.  This is for debugging only.
Send mode for data mode 1 The send modes for data mode 1 are 'P' for Polled
and 'C' for Continuous.  In continuous mode, a '!'<CR> command stops the
stream and the 'S' command restarts it.  To read data in continuous mode,
the application searches for a start header (255).  Once f ound, the rest
of the packet must be read in, the checksum computed and compared to the
packet's checksum.  If the checksums don't match, the application must
reread the data one byte beyond where it last found a 255 and start the
process over again.  Alt ernatively, the application can stop the stream
with a '!'<CR>, pause a few character send times, flush its read buffers,
then send an 'S' and begin reading the stream.  Continuous mode is not
recommended for commercial applications (error recovery is dif ficult and
serial interrupts and CPU cycles are wasted). 

Mode 2: Euler angles mode The Tracker sends yaw, pitch, and roll angles.  
The data format for yaw, pitch, and roll is a signed 16-bit word, where
+16384 = 180 degrees, and -16384 = -180 degrees.  Data packet format for
mode 2 (Binary) The total packet size is 8 bytes.  The byte format is:

   Byte  Description
   0  Header (always 255)
   1  Yaw high byte
   2  Yaw low byte
   3  Pitch high byte
   4  Pitch low byte
   5  Roll high byte
   6  Roll low byte
   7 Arithmetic checksum (Bytes 0-6 added together) 
Data packet format for mode 2 (ASCII)
 
The data is transmitted in the preceding form in ASCII hex with spaces
separating each two byte ASCII hex value.  This is for debugging only.
Send mode for data mode 2 The send modes for data mode 2 are 'P' for Polled
and 'C' for Continuous.  In continuous mode, a '!' command stops the stream
and 'S' command restarts it.  To read data in continuous mode, the
application searches for a start header (255).  Once found, th e rest of
the packet must be read in, the checksum computed and compared to the
packet's checksum.  If the checksums don't match, the application must
reread the data one byte beyond where it last found a 255 and start the
process over again.  Alternative ly, the application can stop the stream
with a '!'<CR>, pause a few character send times, flush its read buffers,
then send an 'S' and begin reading the stream.   Continuous mode is not
recommended for commercial applications (error recovery is difficult a nd
serial interrupts and CPU cycles are wasted). 

Emulation Modes Mode 3: Microsoft mouse emulation mode When in binary mode
and communicating with a mouse device driver, this mode operates at 1200
bps and simulates a 7 bit data byte (with 1 stop and 1 start) by always
sending the last data bit as a simulated stop bit.  The output format is
defined by the Mic rosoft mouse data format (3 byte format).  While
operating in mouse mode, X is determined by a scaled yaw angle calculation.
Y is determined by a scaled pitch angle sensing.  Send mode 0 for mouse
mode

This mode sends values like a mouse.  Delta values are sent as long as the
Tracker moves.  The size of the deltas depends on how far the Tracker has
moved.  Send mode 1 for mouse mode

When the Tracker is first initialized into this mode, a reference position
is taken.  Any movement away from this reference position results in deltas
being continuously sent until the Tracker is moved back to within the
threshold near the reference posit ion.  The size of the deltas depends on
how far away the Tracker is moved from the reference position.  Sensitivity
and mouse mode mickey values

   One X mickey is 1/4 degree change in yaw and
   one Y mickey is 1 degree change in pitch

for a sensitivity of 1.  As sensitivity increases, the change per degree
increases.  Thus, a sensitivity of 2 represents 1/2 degree change in yaw,
etc.  A sensitivity of 0 can be used to disable X or Y mickeys.  For
example, DOOM works best with the Y axi s disabled, where yaw causes the
head to turn and pitch has no effect.  The range for sensitivity is 0-9. 


Mouse threshold settings

The threshold settings determine how far the Tracker has to move before a
packet is sent.  If the threshold is low, a movement in the Tracker will
result in packets being sent frequently (small mickey counts sent
frequently).  If the threshold is high, th e Tracker must move farther
before a packet is sent (large mickey counts sent infrequently).  The
threshold is related to sensitivity in that the movement values are first
adjusted by sensitivity before being compared to the threshold settings.  
The thres hold range is 0-9. 

Mode 4: CyberMaxx emulation mode [Not yet implemented]

Examples
Modes for terminal debugging
!M0,P,A,0,0 Raw polled mode, ASCII, no filtering.
!M0,C,A,0,0 Raw continuous mode, ASCII, no filtering.
Modes useful for applications
!M1,P,B  Cooked polled mode, binary, filtering not changed.
!M1,P,B,0,0 Cooked polled mode, binary, no filtering.
!M1,P,B,3,3 Cooked polled mode, binary, medium filtering.
!M1,P,B,7,7 Cooked polled mode, binary, full filtering.
!M2,P,B,3,3 Euler polled mode, binary, medium filtering.
Emulation modes
Mouse mode
!M3,P,A,0,0 Mouse mode, polled, ASCII, no filtering.  This is for debugging only.
!M3,C,A,0,0 Mouse mode, continuous, ASCII, no filtering.  Transmits only
when the mouse moves.  For debugging only.
!M3,C,B,3,3 Mouse mode, continuous (whenever the mouse moves), binary,
medium filtering.  For true mouse emulation, this command must be sent at
1200 bps to put the Tracker into 1200 bps mode.


Sample Code

/* test.c: Simple program that prints data to the screen. */
/* Uses srcsimplevstrack1.lib. See the devkit disk for more info. */
/* Created 2/17/95 */
/* John Schultz */

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <math.h>
#include "vstrack1.h"

void main(int argc,char ** argv) {
TrackerData td;
TrackerStatus ts;

  ts = initTracker(&td,TP_COM1,9600,timerSecs(2));
  printf("%s.n",trackerInfo(ts));
  if (ts != TS_OK) {
    closeTracker(&td);
    exit(0);
  } // if

  ts = sendTrackerCMD(&td,"!M1,P,Br",timerSecs(2));
  if (ts != TS_OK) {
    printf("%s.n",trackerInfo(ts));
    closeTracker(&td);
    exit(0);
  } // if

  requestTrackerData(&td);

  while (1) {
    float y,p,r;
    if (kbhit() && getch() == 'q') break;

    ts = readTracker(&td,timerSecs(1));
    if (ts != TS_OK) {
      printf("n%s.n",trackerInfo(ts));
      resetTracker(&td,timerTSecs(1));
    } // if
    requestTrackerData(&td);

    y = TOFLOAT(td.euler.y);
    p = TOFLOAT(td.euler.x);
    r = TOFLOAT(td.euler.z);

    printf("x %6ld y %6ld z %6ld y %6.2f p %6.2f r %6.2fn",
      td.magnetic.x,td.magnetic.y,td.magnetic.z,y,p,r);

  } // while

  closeTracker(&td);

} // main

/* test.c */

 (end of quote)


The details about tracker programming are an excerpt of the i-glasses! 
Developers Kit.  This kit consists of a PC version of the glasses, docs,
and a CD with examples and costs $1000.  There will be also a version of
the kit with the developer material only for ca.  $50 (Also the PC version
of the kit comes with a CD with 10 games.) You can purchase this kit
directly from Virtual-io in Seattle (address next time).  You also can get
such material from their ftp site: ftp.vio.com, look into outgoing/docs and
especially the file webdev.doc there.

To give you an idea what the glasses products are aside from the Amiga:
There is a VCR version which is made for a WalkMan-like VCR and is just the
glasses connected to this VCR.  The second product is the "PC" version. 
It's much more expensive, because it also contains a VGA-to-composite
conversion box, and the Head Tracker.  The Amiga version of this product is
not yet defined precisely.  This is because it depends on which Amiga you
use, for the A1200 you need only the glasses and the Head Tracker without
that conversion box of the PC version.  For the A4000, you would need some
Composite modulator or similar, perhaps we have to produce again something
like the A520, this is not yet clear, sorry.  But anyway, for the Amiga,
the kit will probably contain the glasses and the Head Tracker, which
connects directly to the serial Amiga interface.  So you don't need that
VGA-to-composite conversion so that the Amiga version should become
significantly cheaper than the PC version and end up somewhere in the
middle between the Video and the PC version (rough guess currently, no
guarantee).

-- 
Best Regards, Dr. Peter Kittel       //
Private Site in Frankfurt, Germany X/  Email to: peterk@combo.ganesha.com
Now re-employed at Amiga Technologies GmbH in Bensheim, Germany
Currently only rarely reachable via email and news, sorry.