Half-Dome Projection Methods Topic

Post by **BHawthorne** » 11 Aug 2009, 02:46

I know these surround gaming subforums tend to be focused on TH2G and SoftTH, but I'd like to bat around a few other surround gaming methods in this thread that are out there but mostly just concepts. Both of these are using projectors.

First one I'd like to mention is iDome. It's a concept by Paul Bourke that uses a half-dome convex first-surface security mirror to project onto a half-dome screen.

http://local.wasp.uwa.edu.au/~pbourke/miscellaneous/domemirror/

The second one is jDome. I'm not as impressed with jDome, but it's easier to achieve. It's just projection onto a half-dome rear projection screen. I could see that this might have focus issues with the projector.

http://www.jdome.com/

Racer_S was talking about making a utility in this thread: http://www.widescreengamingforum.com/node/10894

Wonder if he would be interested in doing a fisheye and convex mirror pre-warping app too? IMHO, there would be a lot of commonality in the codebase for the apps. The only thing that would keep something like iDome from existing is the pre-warping utility doesn't exist yet. We all could have the option to be doing half-dome projection soon if that utility was available to us.

I'm willing to pay a bounty to someone if they can make the pre-warp utility for the community.

Sir Drip · Post by **Sir Drip** » 11 Aug 2009, 04:28

That aint shit...Look at this

http://www.youtube.com/watch?v=Cqh_F4iN8pg&feature=related

Post by **BHawthorne** » 11 Aug 2009, 04:46

That aint shit...Look at this

http://www.youtube.com/watch?v=Cqh_F4iN8pg&feature=related

The problem with panoramic circular projection like that is the FOV. Sure you get 360 left-right FOV but the up-down FOV sucks bigtime. As is, I can do 151 degree circular projection like that with a TH2G and my 3 720p using Sol7.

Doing 2 half-domes for 360 projection would blow that away. Dome projection is way more immersive. :wink:

Sir Drip · Post by **Sir Drip** » 11 Aug 2009, 04:52

Yea...but give it some time..and add track Ir and problem solved!

Post by **BHawthorne** » 11 Aug 2009, 05:45

Yea...but give it some time..and add track Ir and problem solved!

The problem is FOV. Circular projection can never achieve the same FOV dome projection gives. :wink:

keltie · Post by **keltie** » 11 Aug 2009, 06:35

Hi,

This does raise a common issue with both topics (distortion correction in very wide setups and geometry correction for immersive displays) in that it really needs a multiple camera/view configuration to be done as correctly as we know how. Of course what is acceptable is subjective and is based on user requirements.

I'd happily encourage anyone to get in and discover for themselves how the different approaches work but that can get expensive with exotic setups.

The really tricky thing for these issues in this forum is finding commodity games that will utilise multiple cameras. Some exist but utilise clusters of networked hosts such as FSX and X-Plane (both of which have configurations for 'Elumens' style domes as well). But we want to play of a single host and leverage SLI/Crossfire usually. One of note is rFactor although its camera configuration is hard wired. There is material for another rich thread in driver enabled camera control in a similar manner to Nvidia's 3D Vision attempt - on the fly creation and transforms of game cameras.

For any single view image, you can warp it such that it appears geometrically correct on the projection surface, if you know the distortions that are acting upon the projected image (eg, fisheye lens, spherical mirror, dome, cave etc.). This doesn't mean that you will alleviate the scale and perspective artefacts caused by extremely wide fields of view to create the image but you should at least be able to get a horizon line to draw horizontally.

Traditionally a dome projection concerned with these issues would have four (for half dome) sources or camera views with are then stitched and warped. You probably already found it but Paul describes this process here: http://local.wasp.uwa.edu.au/~pbourke/miscellaneous/domemirror/mirrorrender/

The topic is interesting as it suggests a more correct approach to the edge distortion fix/plugin thread mentioned above. The camera setup is slightly different for the standard triple monitor setup of course. Having gone to multiple cameras though, there are a pile of other issues crop up. The warping process for the dome content addresses some them for that environment. What I would like to share is that essentially it's the same process of correction for a spherical environment as it is for flat/faceted or cylindrical surround environments too (with some caveats and two major distinctions between applications). I'll try and get back with a document describing this.

Garry

keltie · Post by **keltie** » 21 Aug 2009, 15:36

Found it!

Well, sort of. I was nervous about distributing this quite well known info as I couldn't find a reference anywhere that made it public. However, as you can read in the link address, all was not lost.

http://web.archive.org/web/19980703080550/www.trimension-inc.com/specs/trimgeom.html

The article tries to explain, through examples that may be lost to the non IRIX user, of a method for setting up curved projections and also for handling arbitrarily wide FOVs. Note though, while the example given is around a cylindrical screen, the more correct way of doing them is actually spherical, or a portion of the inside of a doughnut. Sophisticated cylindrical screens may have a vacuum backing to suck them into shape! So the geometry warping is actually the same for a dome from the users perspective.

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