Contents

This document gives descriptions and instructions on how to connect a pair of (cheap) stereo glasses to a (SGI) workstation.
 
 

Introduction

This project began when I bought an INDY. I was impressed with it’s capabilities and began looking what it could do.

I saw that it could do real 3D with special glasses. The only thing was that the CrystalEyes glasses from Stereographics were a bit above my budget (See Qualixdirect for prices).

When I a visited a local PC-shop, I noticed they were selling ASUS VR 3D glasses for $30.

Now I thought it wouldn’t be too hard to connect these glasses to an Indy since all these glasses work on the same principle, or at least the glasses which use a standard monitor. So I bought a pair , made a circuit and found out it is indeed very easy.
 
 

What do you need?
 
 

• Workstation (SGI/SUN/Intel) with stereo output
• A pair lcd-shutter stereo glasses
• Some electronic components
• Soldering iron + scrap of PCB
• Strongly recommended: voltmeter (and scope)
• Program that supports Crystaleyes (e.g. battalion, textomatic)

Stereo-sync signal

From the "Hardware Developer Handbook", online at SGI's Toolbox.

"The stereo- sync signal indicated when the system is changing between buffers used to portray images for the right eye and left eye. The signal is a TTL signal where the "high" state indicates the left eye being shown.

There are five different connectors used for the stereo-sync signal –a DB-15 genlock connector, the Powered Peripheral Port, a 3-pin mini-DIN, a DB-9 connector, and as part of the 13W3 connector."

Also see "man stereo". This states that "high" indicates the right eye. On my Indy high indicates right eye, so probably the man page is right. It doesn’t hurt to switch the left- and right-eye. You’ll notice this immediately as the stereo won’t work properly.

There are also some pin-outs in the stereo manual page.

If you really can’t find them, I can sketch them for you since I found them in PDF files.
 
 

Short 3D shutter desciption

When we see 3D, it’s because our two eyes each see a slightly different view. From the differences the distance is calculated. Now on a computer screen everything is the same distance from each eye and both eyes see the same. What we need is some way to get both eyes to see a different view on the same screen.

First we need a good resolution, 1280x1024x120Hz sounds nice. That’s 120 images per second. In the first image we display something for the right eye to look at. The second image is for the left eye and slightly different. The third is again for the right eye, the fourth for the left eye and so on. Now you could blink your eyes alternately 60 times per second, but’s it’s easier to use a shutter that blanks 60 times per second alternately each eye. The shutters used in these glasse are LCD (liquid crystall display).

So your computer would have to put out a signal that signals when to blank for one eye, the other eye will be just the opposite. Most SGI machines have this, some SUN’s, (some) Intergraphs and also some PC’s. Because the principle is the same with all LCD-shutter glasses, you can use this circuit and the ASUS 3D glasses on all systems. You’ll only have to adjust for different voltages used for power and stereo-sync. The stereo-sync can also be deduced from the monitor-SYNC signal, but that’s for later....

For more information look on Stereographics or Stereo3D
 
 
 
 

ASUS 3D glasses VR-100g

These glasses are sold for the ASUS AGP-V3800/TVR and AGP3400TNT with VR-100 upgrade kit.

The specifications on the box reads:
 

Size	50mmx30mm
Weight	75g w/o wire
Working Voltage of LC shutter	10Volts
Consumption current	10uA
Wide Viewing Angle	50 degrees
Operating Temperature	0-50 degrees C
Storage Temperature	-20~60 degrees C

 
 

WARNING

Not everyone is used to the stereo images especially when they have not had such an experience before.

Users should avoid watching the screen for a prolonged period of time, recommended for you no longer than 30 minutes.

Remove glasses if you feel a slight headache or if your eyes become tired.

 

The first time I used the glasses, I indeed had a headache. But then I just got it all working and tried it for 45 minutes. The second time I didn't notice anything.
 
 

I bought these glasses for $30 (f65,-) at Mycom, but these will probably be cheaper in America (I've seen for $15 at an online store).

You can use other sorts of 3D-glasses, just make sure that they are LCD-shutter (not polarized ones) and you need to know the maximum shutter-voltage.

I also read that SGI pushed VESA to make the 3-pin mini-DIN the new VESA standard for connecting 3D-glasses to PC's so maybe in time there will be many (cheap) glasses which can be used with SGI workstations.
 
 

My comments on the ASUS glasses:

• Cheap $30 (or $15 in USA)
• Cheap construction (but stays on well)
• Fits over my pair of glasses
• Boring black color, Indy-blue would be better... I’ll have to find my airbrush.
• Looks easy to take apart (haven’t tried it)

How does the circuit work??
 
 

What we get out of the Indy is:

• stereo-sync signal, 2V
• +12V at 0.5A (some other SGI’s: +10V)
• ground.

What we need for the glasses is two signals:

• one for the left eye, +10V
• one for the right eye, +10V

Luckily the signal for the right eye is the same as the stereo-sync signal, only then with a "high" of 10V, and the signal for the left eye is the inverse of the signal for the right eye. What needs to be done is to amplify the signal to 10V and mirror one signal for the other eye.

For adjusting the voltage to 10V an operational amplifier is used in a comparator configuration. The reference voltage is set at 1V so the output will be the supply voltage – 1V if the input is greater than 1V and 0V if the input is lower than 1V. Now we already have the output for one eye.

For the other eye we use the same circuit but just use the same comparator, but with the opamp input pins switched. This is called an inverting comparator and will give the same output as the other comparator, only inverted.

These two signals can be used to drive the glasses. A divider circuit is used to get the reference voltage for the comparators. When all combined we get the following circuit:

Lines connected are shown as dots! No dots = no connection. And the pin-outs on the second amplifier are different. Use 1 -> 14, 2 -> 13 and 3 - > 12. If the picture shows as a big mess, click on it. Or save to disk and open with another program.

This circuit is verified to work on an INDY (and will therefore work on all other systems with mini-din3).

You can build this circuit on a bit of experimenter’s board. Just make sure nothing shorts out. As extra precaution I used shrink tube on the connectors.

The LM324 is used because that was the first one I found lying around.... You could just about use any op-amp, that doesn’t matter much. We’re only talking about 120Hz.

But if you only have a +10V power supply (Crimson) you might want to use a low-drop op-amp. The LM324 can amplify a signal to the supply voltage – 1V, though the glasses will work at 9V.

So with a 12V supply you will get 11V max. With 10V supply voltage this will be 9V max. This voltage drop is lower with a special low-drop op-amp, but the glasses wil work with either 9V or 11V.

The left and right eye were found experimentally.
 
 

Safety & Testing
 
 

Building this circuit should be relatively safe. But of course accidents can happen and you can blow your SGI system up. This might be a bit of a overstatement, because there probably will be fuse somewhere, but it won’t hurt to be cautious. That’s why I used 3 100mA pico-fuses to protect my Indy. These fuses are fast and will burn through if a current of more than 100mA flows to/from the Indy. Unless you do some real weird thing, your workstation will be all-right.
 
 

It’s also advisable to check the connectors you are going to connect the circuit to, to see if you really have the right connector and the right pin on the connector. With a voltmeter you can check the 12V/10V power signal and with an oscilloscope you can check the stereo-sync (you first need to set the display for stereo-sync or else the ouput will be 0V).
 
 

If you have built the circuit, connect it to a power supply an measure how much power it draws. If it’s more than 500mA you’ve probably done something wrong. Even more than 100mA is much (in that case the fuses will blow).
 
 

Please mail me with any questions, mistakes, information or working circuits at roosmcd@dds.nl
 
 

Summary of SGI systems with stereo output

This list I got from the Hardware Developer’s Handbook, online at SGI website, http://toolbox.sgi.com.

Both the Crimson and the Onyx have a stereo signal in the 13W3 connector. On pin 4 (HDRIVE) the stereo sync signal is present. Pin 5 (VDRIVE) is a +10V power signal for the emitter. These signal might be easy to obtain with a 13W3-5BNC cable, RGB connect to the monitor and the HSYNC and VSYNC cables will hold the stereo-sync and stereo-power signal.
 
 

On the DB-15 (this is not like the PC-monitor connector, that’s HD-15) connector the stereo-sync is on pin 10. However there doesn’t seem to be a stereo-power signal so you would have to use something else to power the circuit.
 
 

With the Mini-DIN 3 connector the stereo-signal is on pin 3. Ground is pin 2 and pin 1 connects to the +12V power (0.5A). This is also the new VESA stereo.

On the DB-9F and DB-9M connectors the stereo-sync signal is on pin 1. The stereo-power signal (+12VDC, 0.5A) is on pin 8. Pin 6 and 7 are marked digital ground return.
 
 

The Powered Peripheral Port (PPP) has a stereo-sync output on pin 3. Pin 8 is a 10V, 0.5A power supply. The ground is connected to pin 7.
 

Please note that I haven’t tested the circuit on all these machines,

Only on my Indy. In theory it should work on every SGI machine

With an stereo output, but you’ll have to check things for yourself.

Use a voltmeter to verify that the ground and power supply signals

are actually there, on the pins mentioned here.

Then check with a scope if you get a stereo-sync signal

(of course, first turn stereo on).

If you notice any faults in this document,

please mail them to roosmcd@dds.nl.

Links

This is the section where I dumped (part of) my SGI bookmarks.

   Click Here

To do

Some projects I would like to do in the future:

• making the stereo glasses wireless, which shouldn’t be too hard. Greatest problem looks like the LCD shutters need 10V and you wouldn’t want 6x1.5V batteries in there. So some sort of step-up generator will be needed. But there are specialized IC’s to do that.
• Measuring the transmission ratio of the glasses and see how well they compare with the CrystalEyes.
• Hooking up a video-projector that does 1280x1024, 120Hz for the real 3D experience......
• Building a midi interface for the Indy
• IR-light and Indycam
• Get a faster SGI :)
• Make this page even more (un)readable...