SceneKit: Transform texture to fill only part of a sphere

Question

I'm developing an application that uses SceneKit API and I faced the problem that I basically cannot apply a texture to a sphere object and keep texture's pre-defined size. I'm able to either scale the texture up to the object's surface (default SceneKit's behavior) or repeat it. But what I want to achieve is similar to the billiard ball:

Let's say I have aa .png image of a white circle with the number "13" at the center of it. I want to put it like the one on the picture. Generally, I want it to be scaled up to a fixed size, not the whole surface.

I use material.diffuse.contents property of SCNGeometry to set the texture and I found contentsTransform property in the documentation which can probably help me sort it out but I didn't find an explanation how to use it with the sphere object.

Is it something that is possible with pure SceneKit? Any help would be very appreciated.

Answer 1

You need a preliminarily modelled geometry (polygonal sphere in your case) and its UV Mapped texture that's made in 3D modelling software (Autodesk Maya for instance).

Watch this short movie to find out how to get UV-mapped texture.