Stereoscopic fun on iOS

[Edit: this app is now available on the appstore, and has a dedicated web page]

The fun never stops with stereoscopic rendering. I posted previously about my earlier attempts with anaglyphs and shutter glasses, and all that was really fun, but not without drawbacks. Shutter glasses are awesome, but the only computer I have with a stereo output is an old SGI workstation, which isn’t up to the task to render modern 3D graphics, and doesn’t event give me stereo OpenGL visuals and a depth buffer at the same time. Anaglyph glasses are cheap and work everywhere, but they mess up the colors and they have a serious problem with ghosting, ruining the stereoscopic effect.

My3D ipod stereo tunnel
So, it was with great enthousiasm that I learned there’s a cheap and simple stereoscopic viewing contraption for the iphone produced by hasbro. It’s sortof like a viewmaster, only instead of cardboard reel with stereoscopic pictures, it has a place to attach an iphone or ipod touch on the back of it, using it as the source of the stereoscopic image presented to the user. What needs to be done iphone-side is simple enough. Just make it display a stereo pair side by side in a split-screen. The only drawback of this approach, is that since the iphone display is split in half, the achievable aspect ratio is slightly less than 1 which has an impact on immersion, making the perception more like looking through a squarish window into the 3D world rather than being surrounded by it. Still very impressive for a 28 dollar plastic widget.

Buying this apparatus gave me the final push I needed to get onto iOS programming. I find Objective-C unspeakably ugly and the Apple APIs needlessly convoluted, which was why I kept pushing this back, but I really wanted to see my code in glorious stereoscopic … glory, so I bit the bullet and ported over the stereoscopic tunnel program I’ve written originally for the SGI when I bought the shutter glasses.

The result is awesome; full stereo 3d without color degradation on modern programmable graphics hardware. Unfortunately one has to use the crippled version of OpenGL that’s become so popular on mobile devices lately: OpenGL ES 2.0 (see webgl post for my rant on that issue), but it was easy enough to make a wrapper that brings back immediate mode and the matrix stack.

In case you’d like to play around with the code, here’s a tarball. Feel free to use it under the terms of the GPLv3. It includes an Xcode project that compiles it for the iphone and a makefile for normal systems. If you run the program on your iphone tap anywhere on the screen to go to the options GUI to enable stereo rendering or change between the simple and the normal-mapped tunnel (keys s and b on the PC version).

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Stereoscopic OpenGL part2

Me with my shutter glassesMy obsession with stereoscopic rendering continues unabated. It’s just so fucking cool to write a bit of code and have 3D objects pop outside of your monitor and float above your keyboard.

Fact is, I couldn’t settle with my crummy anaglyph glasses see previous post. I had to try out proper shutter glasses and quad-buffer OpenGL visuals.

Thanks to nvidia’s policy of supporting quad-buffer visuals and stereo ports only on expensive Quadro graphics boards, and the proliferation of flat panels which are entirely unsuitable for use with shutter glasses due to ridiculously low refresh rates, I couldn’t do that with my PC. On the other hand, my trusty Silicon Graphics Octane2 workstation was more than up to the task as it comes with a stereo synchronization port and quad-buffered OpenGL support out of the box.

So off I go to ebay, where I bought the cheapest lcd shutter glasses I could find, the ASUS VR100 glasses which came once upon a time bundled with some expensive ASUS TNT2 graphics cards as a high-end gimmick.

SGI to ASUS VR100 adaptor circuitConnecting these glasses to SGI workstations has been done before and it was a piece of cake to follow that guy’s schematic and construct the necessary circuit to translate the signals from the SGI stereo port to those required by the shutter glasses.

The only problem I’ve had, is that my Octane2 has the low-end V6 graphics option, which apparently doesn’t provide a z-buffer when using stereo visuals.

3D tunnelNow I didn’t feel like z-sorting all polygons like the good old days when z-buffering was too expensive to use on underpowered PCs while doing software polygon rendering, so I tried to figure out a couple of graphics hacks that I could do which wouldn’t require a z-buffer to look right. So I came up with this swirling tunnel, and a simple wireframe teapot.

OpenGL stereoscopic anaglyphs and patents

An anaglyph is a combination of two images into one, in such a way that they can later be separated by viewing the image through appropriately colored transparent filters. The objective is to present slightly shifted views of the same 3D environment to each eye, in order to achieve depth perception (i.e. really perceive the 3rd dimension).

anaglyph glasses

I’ve never dealt with anaglyphs in the past, but during my recent week-old obsession with stereoscopy, I’ve stumbled upon a pair of free anaglyph viewing glasses (made out of cardboard and cellophane of course). So I couldn’t help but try to find out how I can use them with my own programs.
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