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  • Mon 23 Nov 2009

    Stereoscopy for two users

    Published at 17:07   Category VR Displays  

    How would you allow two users in front of a projection screen to each have their own stereo ?

    I’ve seen such a system in Weimar at IPT/EGVE 2007 and I hear several systems are starting to use this.

    So here are three methods, demonstrated thanks to my Advanced Sketching System (c) :

    Method 1 : Users are separated through a polarized filter


    This can be seen as a regular active stereoscopy system.

    The system has two active projectors, one polarization filter in front of each projector, regular shutter glasses plus matching polarization filters.

    Thanks to the polarization, each user sees only one (active) projector. Each projector displays left and right image as is regularly done with active projectors.

    In theory, you have it, each user sees in stereo ! This is the “easy” way which doesn’t need too much modification apart from adding polarized filters on shutter glasses.

    The active stereo provides a good separation between left and right eyes, but the polarization separation is not perfect, so each user sees a ghost image of the other user.

    This unperfect separation of polarized filters is less problematic when it is used for only one user since the left and right images aren’t that much different. But when you see the picture of another user, it is potentially very different and can also move while you are static. That’s a real presence breaker !

    So let’s try another way :

    Method 2: Users are separated through a shutter mechanism


    Now this can be seen as a regular passive stereoscopy system. For each user, the left/right images are separated thanks to a polarized filter.

    The tricky part : The first (active) projector displays the left image for user 1, then the left image for user 2. At the same time, the second (active) projector display the right image for user 1, then the right image for user 2.

    This means that half the time you can see the left and right images for user 1, then half the time you see the left and right images for user 2.

    But how can you hide the left/right images of the other user ? With modified shutter glasses that shut both eyes at the same time rather than each eye alternatively !

    This method also requires some tricks on the image generator. Often times the generation of left/right images in quad buffers is hardwired in the renderer, so you need a system that is flexible enough to allow the generation of two left images instead of left/right.

    Method 3 : multiple time splices

    Another way is to take the same approach as the active stereoscopy that also requires hardware modifications : draw each image sequentially : User 1 Left, User 1 Right, User 2 Left, User 2 Right, User 3 …

    Shutter glasses would then open only for User 1 left eye, all other eyes/users being shut, then User 1 right eye, etc.

    This has several implications, ranging from flickering if the projector frequency is not enough, to decreased luminosity. You also need special shutter glasses and software to support all this.


    This is not an easy topic! But an important one if we want real cooperation. I’ve left the option for multiple HMDs aside because you don’t see the other user, and some people just don’t want to wear HMDs.

    I’m sure others methods exist, such as this one presented at IEEE VR 2009: Image Blending and View Clustering for Multi-Viewer Immersive Projection Environments, Jonathan Marbach

    Do you know other methods ?

    Fri 20 Nov 2009

    Twitter & Newsletter

    Published at 16:31   Category Perso  

    I’m finally starting using Twitter, codename VRGeek (what else?). I don’t know yet how I’m going to use it, but probably just post links to interesting VR stuff when I don’t have time or not enough resources to speak about it.

    I’ve also added a newsletter to the blog, which will simply send you the latest articles by mail. It seems not everyone is fond of RSS !

    You can subscribe to the newsletter thanks to the widget on the right column of the blog.

    There’s also a fancy new tag cloud !

    Now you can’t miss anything I’m saying !!

    Maybe next week I could start a TV show ? =)

    Wed 18 Nov 2009

    3DUI Grand Prize registrations are closed

    Published at 0:01   Category VR Applications  

    Just a small word to say that 21 teams have registered to the 3DUI Grand Prize !

    We’re very happy about that, we didn’t expect that much participation =)

    All the big 3D user interfaces labs are participating with at least one team, and we also have one private company (you know who you are!)

    We’re sure we’re going to get very interesting solutions and we hope that this contest will give a small boost to the 3dui field !!

    Again thank you all for participating, and have fun while working on it !

    Mon 9 Nov 2009

    Characteristics of Professional HMDs, by Sensics

    Published at 16:50   Category VR Displays  

    Sensics, makers of the renowned piSight HMDs has released a very interesting white paper called “Characteristics of Professional HMDs“.

    Here’s the introduction :

    As of July 2009, the perfect head mounted display (HMD) – the one providing exceptional immersion, superb image quality, a wireless and featherweight design for a ridiculously low price – does not exist. However, many users might find that a ‘good enough’ HMD can be found for their particular application. This document discusses the key attributes for HMDs, explains why they might be important, and offers some selection guidelines.

    Thanks to them for writing and sharing this document !

    Fri 6 Nov 2009

    VR with a single computer

    Published at 14:23   Category Virtual Reality  

    If you think VR is complex and requires a good understanding of the hardware involved (among many other things) … you’re right.

    But, when you look closely, you don’t necessarily have to use a lot of computers to have a good VR system. In fact most of the VR systems work with only one computer.

    I’ve started a page here showing all the different systems you can create by using only one computer, ie no clustering issues \o/ !