Projectors and 3D and Ghosting/Flicker Removal
Posted: Sun Mar 11, 2007 7:41 am
OP 28/05/2007
A lot has been already covered in other places. I will not add every piece of information there is on projectors on here.
Instead, this will be a short introduction into projectors and an overview of potential problems.
Let me introduce myself. I have been into stereo gaming since I first heard the word "shutter glasses". I have had many stereo setups including normal monitor, Head mounted display, and Projector.
I can, then, wholeheartedly say that out of all, projection was by far the most "Wow"-ing.
Projectors project a large image onto a screen (duh!). When you play on a CRT or even an HMD, the perceived screen size is too small for a "lifelike" size and feel.
In my opinion; on a small screen compared to a larger screen, the smaller screen always gives the impression that you are playing with small toy models rather than a simulation in real life. This is especially noticeable in FPS games.
On a projector, your gun is life size; your enemies are life size. When you stand and look down a corridor in 3D, you ARE actually looking down a corridor - There is no ghosting or other perspective artefacts.
Your focus is also further away at the screen, which means that there is practically no strain.
On top of that, you can watch all your movies and TV shows on your expensive investment.
Wow! That sounds amazing... what's the catch?
There are a few catches. Firstly, there is the initial cost of the projector and the maintenance cost ie bulbs. My projector bulbs last 1000 hours (read a couple of months) and cost ?470 to buy, although I believe that this is the very high end in pricing.
Secondly, not all projectors are stereo compatible. Only DLP projectors work in stereo, and then only a few. There are lists of which do work at other places.
The ones that do work sometimes do not sync perfectly, so you get ghosting. The good news is that this is not like the ghosting on a CRT and can be 100% eradicated.
Thirdly, brightness is always an issue. Projectors just arn't bright enough for shutter glasses use as shutter glasses block out 76% of the light. You have to compensate by notching up the gamma and vibrance settings.
Taking all this into account, if you are looking for the ultimate stereo experience, projectors are the only way to go, followed closely by HMD.
Playing games like half-life2, you really do feel that you are there.
Finishing up on a few tidbits...
If you have the money, you can invest in a dual projector setup. Each projector displays a seperate image from a separate perspective (think i-max). No need for shutter glasses. With the use of polarising lenses and a special screen, you can view with cheap polarized glasses.
There are threads around the internet which list which projectors are compatible; which, if people are genuinely interested, I can hunt out.
Here is one:
http://forums.stereovision.net/viewtopi" onclick="window.open(this.href);return false; ... 89&forum=2
About the bulb, there is a workaround. I have modified my projector electronics to make it accept a bulb and control gear of my own choosing at a fraction of the cost.
A hardware solution and premise for projector ghosting removal that I made can be found here:
As always, I am available for help with any stereo related problems on MSN.
Edit 1:
28/1/2008
This circuit can be converted to a flicker removing circuit quite easily. This particular flicker I refer to is the one you sometimes get every few seconds on random occasions - some people more than others - which is very annoying. The flicker pulls you out of the 3D world and the "suspension of disbelief" is shattered thereby detracting from the experience.
The flicker occurs because the graphics card fails to send an appropriate DDC signal to the emitter. We have to then make our own signal to compensate.
The best way to do this is to use a 50% duty cycle oscillator at the refresh rate you are playing at. Simply connect the 555 timer in oscillation mode (instead of delay mode shown above) using the appropriate resistor/capacitor combination from the data sheet of the timer. Now connect the DDC signal to the RESET pin of the oscillator and the output to the emitter and calibrate to 50% duty cycle at your refresh rate.
Now, what will happen is the falling edge of the DDC signal will continually reset the oscillator thereby keeping the glasses in sync with the refresh rate AND the oscillator will continually produce a square wave. In the event that the signal dies on the DDC line, a reset is no longer triggered and the oscillator will still give an almost perfect square wave keeping your glasses functioning perfectly. The flicker from DDC signal corruption will be completely eradicated as now, whenever the DDC signal is corrupted, the oscilator will take over.
Of course this also means that the glasses will keep on working even out of stereo, so don't forget to turn them off if they run on batteries ;P
-- Shahzad Ali
Cambridge
England, UK
Edit 03/04/2009
Fixed broken links.
A lot has been already covered in other places. I will not add every piece of information there is on projectors on here.
Instead, this will be a short introduction into projectors and an overview of potential problems.
Let me introduce myself. I have been into stereo gaming since I first heard the word "shutter glasses". I have had many stereo setups including normal monitor, Head mounted display, and Projector.
I can, then, wholeheartedly say that out of all, projection was by far the most "Wow"-ing.
Projectors project a large image onto a screen (duh!). When you play on a CRT or even an HMD, the perceived screen size is too small for a "lifelike" size and feel.
In my opinion; on a small screen compared to a larger screen, the smaller screen always gives the impression that you are playing with small toy models rather than a simulation in real life. This is especially noticeable in FPS games.
On a projector, your gun is life size; your enemies are life size. When you stand and look down a corridor in 3D, you ARE actually looking down a corridor - There is no ghosting or other perspective artefacts.
Your focus is also further away at the screen, which means that there is practically no strain.
On top of that, you can watch all your movies and TV shows on your expensive investment.
Wow! That sounds amazing... what's the catch?
There are a few catches. Firstly, there is the initial cost of the projector and the maintenance cost ie bulbs. My projector bulbs last 1000 hours (read a couple of months) and cost ?470 to buy, although I believe that this is the very high end in pricing.
Secondly, not all projectors are stereo compatible. Only DLP projectors work in stereo, and then only a few. There are lists of which do work at other places.
The ones that do work sometimes do not sync perfectly, so you get ghosting. The good news is that this is not like the ghosting on a CRT and can be 100% eradicated.
Thirdly, brightness is always an issue. Projectors just arn't bright enough for shutter glasses use as shutter glasses block out 76% of the light. You have to compensate by notching up the gamma and vibrance settings.
Taking all this into account, if you are looking for the ultimate stereo experience, projectors are the only way to go, followed closely by HMD.
Playing games like half-life2, you really do feel that you are there.
Finishing up on a few tidbits...
If you have the money, you can invest in a dual projector setup. Each projector displays a seperate image from a separate perspective (think i-max). No need for shutter glasses. With the use of polarising lenses and a special screen, you can view with cheap polarized glasses.
There are threads around the internet which list which projectors are compatible; which, if people are genuinely interested, I can hunt out.
Here is one:
http://forums.stereovision.net/viewtopi" onclick="window.open(this.href);return false; ... 89&forum=2
About the bulb, there is a workaround. I have modified my projector electronics to make it accept a bulb and control gear of my own choosing at a fraction of the cost.
A hardware solution and premise for projector ghosting removal that I made can be found here:
As always, I am available for help with any stereo related problems on MSN.
Edit 1:
28/1/2008
This circuit can be converted to a flicker removing circuit quite easily. This particular flicker I refer to is the one you sometimes get every few seconds on random occasions - some people more than others - which is very annoying. The flicker pulls you out of the 3D world and the "suspension of disbelief" is shattered thereby detracting from the experience.
The flicker occurs because the graphics card fails to send an appropriate DDC signal to the emitter. We have to then make our own signal to compensate.
The best way to do this is to use a 50% duty cycle oscillator at the refresh rate you are playing at. Simply connect the 555 timer in oscillation mode (instead of delay mode shown above) using the appropriate resistor/capacitor combination from the data sheet of the timer. Now connect the DDC signal to the RESET pin of the oscillator and the output to the emitter and calibrate to 50% duty cycle at your refresh rate.
Now, what will happen is the falling edge of the DDC signal will continually reset the oscillator thereby keeping the glasses in sync with the refresh rate AND the oscillator will continually produce a square wave. In the event that the signal dies on the DDC line, a reset is no longer triggered and the oscillator will still give an almost perfect square wave keeping your glasses functioning perfectly. The flicker from DDC signal corruption will be completely eradicated as now, whenever the DDC signal is corrupted, the oscilator will take over.
Of course this also means that the glasses will keep on working even out of stereo, so don't forget to turn them off if they run on batteries ;P
-- Shahzad Ali
Cambridge
England, UK
Edit 03/04/2009
Fixed broken links.