I’m doing some research for a project and am trying gather as many solutions/approaches as possible to the following challenge:
If you have a 2D image of a sphere, how would you use that image to texture a 3D sphere? The solutions don’t need to exclusively use Blender, for example, they may use Substance or PS for certain stages of the workflow.
For example, as demonstrated in the attached image, you could:
add a sphere to your Blender scene
remove faces to create a half-sphere
use mirror modifier to recreate the sphere
use UV project to directly project your image onto the sphere
Limitations are that you get significant stretching on the sides of the sphere. This could be manually painted out or perhaps there are other ways to overcome this stretching?
Any thoughts, experiences, tips would be an amazing help. Thank you.
Welcome to one of the oldest problems in the world- mapping a map onto a globe
Long story short is that there’s no good way to do this without dissecting your circular texture. Slightly longer story- go look up the different globe projections and learn about the limitations of each. Fact is, there’s no way to map a 2D texture onto a sphere without some stretching- be it a circle, rectangle, whatever, you’re going to get stretching.
My favorite visual aid for this:
All of these circles are the same size geographically. In this case, the stretching is going the other way- from sphere to texture- but the mathematical causes and distortions are exactly the same.
In this particular case, your best bet would be to slice the circle up into a lobed projection - something like this:
If this isn’t an option, then I would take what you already have, bake it onto a new image, and then clean up the stretched edges with the clone brush in Photoshop
Hard to say based on the limited info. In principle its as @joseph already said. You need a fitting mapping that describes how to transfer the image to the sphere. But if you say its a 2d image of a sphere, that can already contain deformed and projected image content. So if you eg took a photo of a spherical object, then there is lens distortion and perspective projection is already part of what you see on that photo. You may want to use an inverse mapping to eg a spherical or equirectangular format as inbetween to make in more generally applicable. And different photos if not shot similarly will need a different treatment based on distance, angle, camerasetup to be comparably mapped to that planar format. You will also very likely face differently distributed texel densities and blurred areas on the final textured surface based on what material and mapping you are using. So it depends alot on what kind of 2d images you have there.
If its about getting small images of 2d circles distributed on a sphere and slight distortion doesnt matter then you could also think about using one the decal addons available, or generally project it along the inverse surface normal.
It’s basically the same as if you have a front photo of cabinet/cupboard and want to texture this on some box like model… you could try some camera mapping for the UVs but at the sides it will stretch… if it even does show the side a tiny little bit (because of the perspective).
→ You need also some texture from the side, top, back, bottom…
For a sphere the simplest thing would be triplanar (or sixplanar) mapping and mixing from all sides…
The to solve you specific problem you should answer the question:
What is it for or from?
Somekind of generated planet or moon texture ? Or even for the moon ?? Then there are textures in th web (NASA for example)…
