I’d like to bend the UV space like this:
With one parameter specifying the bend amount.
I’m not terribly good at math so I’d appreciate any
pointers or examples. 
What are you trying to achieve with this?
I need to bend a WPF textbox control so I need to make a WPF shader
effect for that which is basically a HLSL shader which gets the image
of the control as input.
Text-on-path is not directly supported in WPF and both hacks I found
for it were quite involved and had serious downsides.
Since I’m working on a pie menu system I figured that this bending
effect might be useful for other things too.
It seems that polar coordinate conversion is the actual name of the effect.
I found a few examples, even a HLSL shader although it doesn’t seem to
work…