I'm going crazy ... spherical mapping

[Metin_7]

Hi guys,

Got a burning question for you. I've made a displacement map for some craters on a planet. But I get that well-known distortion at the poles. The map has a 2:1 aspect (3600 x 1800 pixels) and loops both vertically as well as horizontally. How do I perform the necessary polar distortion at the bottom and top of the image. I've tried Photoshop's polar coordinates filter, but that doesn't make my image ready to map on a sphere, but that doesn't give me the effect I need (polar distortion at both top and bottom, like in those famous NASA planet maps).

An other solution might maybe be correcting the distortion in the UVW mapping of the sphere, maybe with UVW Unwrap or so? Or maybe rendering the map with a spherical VRay camera could be the solution?

If you could help me out I'd be grateful.

Thanks in advance,

Metin

[RErender]

Richard has just what ya need http://www.richardrosenman.com/photoshop.htm

[Metin_7]

Thanks RErender,

I was initially very happy with Richard's plug-in, but it processes the distortion into the map in a way that seems to scale the line width out of the image boundaries, resulting in the map losing its seamlessness and causing an ugly vertical seam when mapped on a sphere. The map should stay loopable by horizontally scaling while wrapping around.

I'm losing too much time with this problem.

Cheers,

M7

[Metin_7]

In these kind of NASA maps, the map remains seamless regardless of how close to the poles the pixel lines are:

http://www.oera.net/How2/PlanetTexs/..._2500x1250.jpg

I assume that they first created a seamless panoramic map and then executed the image processing algorithm on the bitmap to create the polar distortion.

[GoncaloP]

Try to reduce the blur value, maybe it can help...

[UBIKmh]

Have you tried your map in PS with polar coordinates distortion. I used this tool alot with 360 sky that I made with Bryce. Using these skies straight will get this vacuum cleaner effect when you look up. Using polar distort with rectangular to polar, you recreate this effct in PS. With some painting you take it out and then do polar to rectangular.

Hope this can solve your problem.

Marc

[Metin_7]

Thanks for the new replies guys.

I'll illustrate my problems with some clearifying imagery ...

This is the map I've created in Photoshop to get some cartoony moon craters:


This is what it looks like when VRay-displaced on a standard sphere:


This is the same map when I use rectangular to polar distortion in Photoshop (as you can see there is nothing much to paint away with the sharp shapes):


This is the map after using Richard's Photoshop plug-in:


And this is what that looks like on the same 3D sphere as above:

[Metin_7]

A remark: if you look at the distortion in the NASA maps, the amount of stretching seems not to be as gradually changing as with Richard's plug-in. A large area in the middle looks almost frontal, then there's a relatively fast evolving stretch at the top and bottom.

Cheers,

Metin

[Metin_7]

I found a solution. Will post details in a few moments.

Cheers,

M7

[Metin_7]

Here we go. Spherical Metin mapping (TM) ...



I leave it up to you to figure out my method.

Cheers and thanks again for your suggestions,

Metin

[RErender]

No hints? :P

[RErender]

Works pretty good if you map a cube with spherical mapping and then use a spherify modifier, probably not your method though

[Metin_7]

You win the first prize!

Advantage of this approach is that the sphere is not polar.

Cheers,

M7

P.S.: I didn't use spherical mapping on the cube but I used cubic mapping, because the UVW mapping still causes pinching poles in its projection method, or am I wrong?

[RErender]

There wasn't really "pinching" but there was some scaling I'll try it with cubic

[DP]

Metin_7 - thats a neat trick....i wonder how it will work with something really tight like a golf ball, they are bitches to map