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Sphere Wrapping (Read 1050 times)
SpaceRibs
Sphere Wrapping
Aug 2nd, 2007, 4:36pm  
This is a bit of a heavy request but it would be great to get some answers for this. I'm currently developing a program for the Maryland Science Center where students are able to create Diatoms and then drop them into a sea of other user generated single celled organisms. We are currently in talks with a few other corporations, one of which is the Magic Planet spherical projector which takes any prewrapped spherical image and screen captures it to the display. http://www.globalimagination.com/

I would love to take the already created rectangular "Sea" and warp it so that it works on this wonderful display but I don't even know where to start. If anyone has and ideas i'd love to hear them.
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V
Re: Sphere Wrapping
Reply #1 - Aug 2nd, 2007, 5:48pm  
hmm that looks great? how does it work?

do you take a rectangular texture and just map it into a sphere ?
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Victor Martins | www.pixelnerve.com/v
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extrapixel
Re: Sphere Wrapping
Reply #2 - Aug 2nd, 2007, 7:14pm  
Most probably this is just a warped mesh with a texture.

I'm currently working on a tool to pre-warp graphics to be projected on non-plane surfaces. The mesh consists of a defined amount of bezier-curves that can be freely edited.

However, to get your image mapped on a sphere you must transform your mesh into a polar mesh. Just think of it as a rectangular grid, maybe with your "sea" as texture. This grid, actually a set of polygones, has to be warped around a pole. So , bottom left and bottom right corner of the grid share the same x/y coordinates. Top lef, top right corners are the "pole", so they share the same x/y-coordinates too.
Not sure if this makes sense... I'll post some screenshots later today to make it more clear.

Paul Bourkes webiste is a great resource for all kinds projection related stuff:
http://local.wasp.uwa.edu.au/~pbourke/projection/

Does globalimagination probably provide a tool for realtime warping? If so, you don't have to care about the distortion, but only "connect" the both ends of your world, so one can wander around the globe.

good luck!

ps: google search terms: projection distortion, image warping, off-axis projection
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http://www.extrapixel.ch
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SpaceRibs
Re: Sphere Wrapping
Reply #3 - Aug 3rd, 2007, 9:02pm  
extrapixel wrote on Aug 2nd, 2007, 7:14pm:
Most probably this is just a warped mesh with a texture.

I'm currently working on a tool to pre-warp graphics to be projected on non-plane surfaces. The mesh consists of a defined amount of bezier-curves that can be freely edited.

However, to get your image mapped on a sphere you must transform your mesh into a polar mesh. Just think of it as a rectangular grid, maybe with your "sea" as texture. This grid, actually a set of polygones, has to be warped around a pole. So , bottom left and bottom right corner of the grid share the same x/y coordinates. Top lef, top right corners are the "pole", so they share the same x/y-coordinates too.
Not sure if this makes sense... I'll post some screenshots later today to make it more clear.

Paul Bourkes webiste is a great resource for all kinds projection related stuff:
http://local.wasp.uwa.edu.au/~pbourke/projection/

Does globalimagination probably provide a tool for realtime warping If so, you don't have to care about the distortion, but only "connect" the both ends of your world, so one can wander around the globe.

good luck!

ps: google search terms: projection distortion, image warping, off-axis projection


From what the representative was telling me and showing me, the application they have can prewarp certain graphics and overlay them on top of other graphics but for something that engulfs the entire globe it would need to:

1. Make sure that the diatoms copy over to the other side of the screen when it gets to a boundary.

2. Prewarp the graphic so that it would be similar to something like this: http://math.hws.edu/eck/cs324/s04/lab10/earth_sphere.jpg

3. Setup my resolution to a 2:1 ratio (the bigger the better)

Anyway, thanks for the info, i'm gonna be doing a lot of researching about this over the next few weeks.
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