Based directly on the code of Tiles Reflections plugin from Paint.net source (vers. 3.10)...
Just few ideas to implement in a next Paint.net version... ( nb: since then some functions are now inculed in the built-in effect, except the X/Y distinction! )
The square size is from 1 to 5000px.
The curvation is from -5000 to 5000 allowing more spectacular effects (IMO).
And you could choose each value (angle, size, curvature) separatly for X and Y.
Try it !
This plugin is added to the menu Effects, submenu Distort.
Download the DLL
Here is the DLL
How to install?
Unzip and place the DLL in your Effect folder usually: C:/Program Files/Paint.NET/Effects
UI and Examples: