spherical projection

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spherical projection

Postby matt_knelsen » Thu Jul 02, 2009 8:55 pm

Hey guys,

I'm trying to make a map, in Gmax, to a spherical projection in Pandoras Box, in which 4 projectors are going to be used for a 360 degrees projection. These projectors are not in the exact same condition of height and distance, though they are very proximate. But I'm assuming that I can correct those little differences during the sphere mapping. So, as far as I could understand, in Gmax, I create a sphere, transform it to a editable poly, edit the geometry according to the perspective of the projectors, and finally, apply the UVW Map to adapt the texture to the geometry accordingly. So far so good. The thing is, I have not been able to make the texture mapping behave accordingly to my modeled geometry. When I export the .x objects to Pandoras Box, I obtain different texture coordinates from each projector, and I can't match those differences using layer properties, since when you use meshes, you lose the editing of such properties as LinX, LinY and Keystone. So, I found that applying a second modifier to the geometry in Gmax, Unwrap UVW, helps to fit the texture map more properly to a spherical surface, but still, it is very complicated to match 4 different projector conditions, even if such conditions are very close to each other.

Am I completely misunderstanding spherical surface mapping? Do I always have to have the same conditions to all projectors in a case of a spherical projection? What is the best way to map a spherical surface in order to send it to Pandoras Box?

Thank you!
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Re: spherical projection

Postby matt_knelsen » Thu Jul 02, 2009 10:24 pm

A P.S.: I am using a spherical UVW mapping configuration, but one thing I have noticed is that Pandoras Box does not recognize it, and instead, applies the texture mapping as if it was a plane, and not a sphere, so the texture does not follow the circumference. What am I doing wrong?
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Re: spherical projection

Postby Julia Foest » Fri Jul 03, 2009 10:46 am

Dear Matt,

you won´t get the desired result when editing the mesh first and then applying UVW mapping. You have to do it the other way round: apply the UVW mapping and then editing your mesh.

The way I would warp a sphere using gmax is to load the PB Native 4:3 gmax file (you can download it here: viewtopic.php?f=61&t=148) or just creating a plane and adding an UVW mapping. For the rough mapping I also use a FFD Box, and then for the fine adjustment editing the single points.

Do the same procedure on all four projectors (best thing is to have same lenses and distances, but it is not a must!), and assign the exported x-files to the according cameras.

I hope this answers your questions?

Best regards,
Julia
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Re: spherical projection

Postby matt_knelsen » Fri Jul 03, 2009 3:10 pm

Hey Julia, many thanks for you reply!

What I was trying was to start from a basic spherical mesh, so I wouldn't have much work in order to have my mesh fit my projection surface. Then, once I had my mesh done, I would apply the UVW map, which was spherical as well. So what you are saying is that I can't work with other types of geometric forms beside planes? I'll try to use your method and I'll get back w/ya soon.

Thanks again!
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Re: spherical projection

Postby ricky » Fri Jul 03, 2009 4:42 pm

Hi Matt,
why don't you use PB WARP to create the mesh? It's definitely easier and the result is the seme! You don't have to imagine to create a sphere to project on a spherical object, the aim is to obtain a planar projection and not 3D because the sphere's surface is planar for your eyes. Otherwise you can create a real 3D mesh using gmax like a cubes, spheres, torus, cones.....and you have to apply UVWmap to fit the texture on those mesh. The method to adjust the LinX, LinY is to apply more FFD to have one center shift in the horizontal side and one center in the vertical one.
Regards
--ricky--

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