Mesh transform on rotating control as in Apple's Camera app

[mathiasgithub]

Thanks for the great project Ciechan

I'm trying to create a rotating control as in at the bottom of Apple's Camera app:

However, I'm not able to get the math right. I guess it is similar to buldgeMeshTransformAtPoint although it doesen't buldge out in the center, but caves in towards the edges. Do you know the solution to this?

-Mathias