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-   -   stereo 3D questions (http://www.nvnews.net/vbulletin/showthread.php?t=162714)

skullmunky 05-21-11 05:26 AM

stereo 3D questions
I'm setting up some projection VR systems, and have a couple questions. Currently I'm using passive polarized projection with two projectors, and a QuadroFX set in Twinview Clone Stereo Mode (mode 4).

1. Is that quad-buffered stereo method only available on Quadro cards? If I want to use a similar setup on a GeForce card do I have to use the lower-level method of manually rendering the two viewpoints?

2. If I want to do two walls, say, can I just put in two GPU's, attach two projectors to each, and put them both in clone stereo mode?

3. Now, on active stereo (I'm looking at the Lightspeed DepthQ projector, for example), is there any real difference between the Nvidia 3D Vision system and the shutterglasses that have been around for decades, other than the fact that it can now use an emitter attached to the USB port instead of the 3-pin DIN jack on the card?

4. For active stereo, can you attach two stereo displays (like two of the above projectors) to the two heads on the GPU?

5. I've heard that I need something called a "Genlocked Quadro." back in the day I remember genlock being a box that all your VCR's attach to for editing and mixing with the Amiga Video Toaster :afro2: Is this nowadays just a feature of specific cards, or an external device?

6. extending (4), if I have two GPU's with two heads each, does that mean I can has 4-wall CAVE?

AaronP 05-22-11 12:46 PM

Re: stereo 3D questions
1. Yes, quad-buffered stereo is only available on Quadros. However, you do need to render both eye viewpoints in your application using the GL_LEFT and GL_RIGHT draw buffers.

2. If you want two display walls displaying the same thing with passive stereo, you'll need to use two GPUs and either configure Xinerama clone mode or use SLI Mosaic.

3. There are some technical differences that make NVIDIA 3D Vision better suited to LCD monitors, while the old-school glasses (at least the ones I've seen) are better suited to CRTs. In addition, 3D Vision Pro lets you use RF for synchronization instead of IR, which works better when there's a lot of interference in the IR spectrum (multiple emitters, fluorescent lights, daylight, etc.) Due to difficulties in Linux's USB subsystem, you currently still have to have the 3-pin DIN cable connected to the stereo emitter.

4. You should be able to have two active stereo displays on a single GPU.

5. Genlock and framelock refer to a board that connects a pair of GPUs together and synchronizes their displays. You can also network these boards together to synchronize multiple PCs. You need this for active stereo across multiple GPUs because otherwise their displays are driven by different clocks that might drift. See here for more details:

6. Yes, you should be able to.

AaronP 05-22-11 12:49 PM

Re: stereo 3D questions
Oh, I should mention that even if you're using passive stereo with multiple GPUs, you might still want a G-Sync board because otherwise the two GPUs might flip at different rates and you'll get an annoying issue where one of the stereo displays is displaying frame n while the other is displaying n+1. G-Sync lets you synchronize those flips.

skullmunky 06-25-11 11:52 PM

Re: stereo 3D questions
Ah, thanks! That helps. So for a 4-wall, active-stereo projection system, it sounds like I would need 2 QuadroFX cards and a matching G-Sync card.

For the passive stereo questions, what I was actually thinking of was two passive-stereo polarized projections showing different views (front wall and side wall, or front wall and floor, for example).

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