UV problem -how to project an uv sphere stereographically?

What I’m trying to do is to have a stereographic rendering of a scene.
Right now I’m using an UV sphere with a mirror surface and bake the reflections,
then render the sphere with a perspective camera.

Thus, a pixelated image is rendered and at the end it lacks a large bit of quality.

Is there a way, to map the uv of the sphere stereographically at the first place?

Current rendering:


-in larger size: http://fc06.deviantart.net/fs71/f/2014/331/5/0/staircase_rendering_by_lazururh-d87u1f4.png

It is to be printed at A1 size, thus I would improve it if possible.

In a dirty way, you can render with a panoramic camera, and then use panotools to change the equi-rectangular to stereographic projection.
there may be other ways to accomplish these results, but can’t recall any. :confused:

can you give more details of what you’re trying to do?

Do you want to map the sphere? or you have a scene and want to get the map? or anything else?

My goal is to improve on that image.
Currently the aliased part is distorted so the small pixels are smudged into large blurry blocks to the sides.

I am searching a way to reduce the stereographic projection -the baking to a sphere as the first projection, and the perspective camera as the second- to one
-as, the sphere’s unwrapped image baked would show a stereographic projected scene.

In that matter, either to make a custom uv layout of a regular uv sphere that is correct, or
to model a sphere with a topology that can be easily unwrapped to show equivalent.

i’ve played a bit with the x’y’=(x/1-z, y/1-z) formula that I look in the wikipedia, and came out something like this:


the grid is on the sphere material, and on the plane is just a colored shadow.
Can this be usefull?

Thank’s for the efforts!
If the sphere has a topology same as the texture, than it is closer.
Like that black grid: http://upload.wikimedia.org/wikipedia/commons/5/5c/CartesianStereoProj.png
So then it could be unwrapped straight as the colored shadow looks.

I’m now building up sections from it as svg-s with inkscape, maybe that will work.

In my setup, the sphere is a normal UVSphere, so no special topology was used. The nodes make the stereographic projection of the texture.

I’ve also clamped and scaled the coordinates of the texture from [-1,-1] to [1,1], but this can be changed.
In the example on your #7 post, the grid is scaled from [-5,-5] to [5,5], so changing this in the nodes, and of course, if you use a simple grid texture (not the color grid as I used) you’ll get exactly the same result. :slight_smile:

The nodes still need a better design to be more manageable… I’ve just spent a few minutes with this, and didn’t pay to much atention to make it easy to change, thought all the math is already there.

edited: Another test, this time with a [-5,5] grid:


Never mind, got this topology by manual modeling.
25600 faces, covering a 2*172° field of view.


Thank’s again.

are we talking here about reel stereographic images?
like using these red/ blue lens goggle?

happy bl

No, that’s stereoscopy.