I’m doing the model for AR Color book. User can color on the picture and use an apps to show in AR 3D. They said user color actually is doing texture, color on its UV, so the UV next to same as the picture / camera show.
Jesus... There is no way to do this without overlapping. If it can be seen only from one angle in ar, overlapping isnt a problem. If it can be rotated, or it turns based on your view, it is a problem, and then you should just do a regular uvmap with no overlapping. The guys uvmap in the video was overlapping too though.
That workflow the guy is using in the link is terrible. As I said in my first post, look into camera projection. It's what it's used for in VFX/matte painting. I don't know much about AR colouring, but I assume you can rotate and colour in 360? The guy in the video is basically trying to do manually what camera projection…
I don't think you need to hand make such uvs. A shader can be made that uses the screen coordinates to do this kind of projection. In theory, you don't even need uvs. Or maybe I misunderstand what you are trying to do. Once I made a mesh painter application and you could paint the mesh just like in any 3d texturing…