To: T Goodwin 
In-reply-to: T Goodwin's message of 14 Mar 1996 19:07:02 GMT
Subject: Re: Tech:VGA Buffers, VR, stereoscopic display, synchronisation
References: <[email protected]>
In article <[email protected]> T Goodwin  writes:
>Abstract:-
>Using LCD shutter glasses with a standard SVGA monitor,  generate a 
>stereoscopic display with an increase in frame rate /quality for a limited 
>cost. 

I have experimented with LCD shutter glasses. I have a Sega LCD shutter
glasses connected to serial port of my PC. I have used normal frame
rates and two display buffers to do my 3D experiments. Usually it
is not practical no increase the frame rate of the monitor, because
many monitors have quite slow phosphor. It depends on monitor how
well this works.

>Ideas:-
>To increase frame rate / quality without reduction in screen size. 
>1. Utilise two graphics cards in one machine - one to generate left image / 
>the other the right image. 
>2. Utilise two identical PC�s, synchronised with one generating the left and 
>the other the right image. Output from PC�s to be toggled and output to SVGA 
>monitor / projection unit.
>Of the two ideas, the latter is more viable due to the specialist programming 
>being required for the first. 

>Control:-
>Use standard mouse/keyboard etc. with the cable spliced and connected to both 
>PC�s.

There are some problems in this configuration. PC keyboard interface
is bidirectional (since IBM AT) and you just can't easily connect 
the keybaord to to PC. One of the problems is that PC needs to received
the reset status code during bootup. Another problem is how to handle
the situation when PC is sending commands to keyboard etc.

Serial mouse is easier. The serial data can be easily split to two computers.
The mouse identification is problmenatic, because microsoct mouse
uses DTR line for resetting mouse and when mouse is resetted, it
send an ID byte to computer. This resetting is done by mouse driver
and it uses ID to check the mouse type. You migh get around this
using driver that does not do that or can work witjout ID byte.

There are links to documents of mouse port and keyboard is
my www-page at http://www.hut.fi/~then/electronics.html

One idea is that one PC has the controls and it send the controlling
and syncronization info to the second PC using serial port.

>Synchronisation:-
>The 2 graphics card outputs need to be synchronised so that when the �sync 
>return� is sent the output is switched* to the other graphics card. Thus in 
>effect generating field sequential stereo graphics. 
>Two methods:-
>1. Hardwire the clocks together (college wouldn�t allow).
>2. Use buffers as Time Base Correctors on the graphics card output�s.  

>*Switching:-
>Switching between the two graphics card output�s needs to be done whilst 
>vertical blanking occurs.
>Information Required:-
>1. Other possible methods of synchronisation.
>2. Using buffers (what type etc. (circuit diagrams etc. most welcome)) .

>3. Switching methods. 

How about fast video analogue switches. There are such curcuit avalilable
from many manufacturers. Check for example Maxim.