Launchpad Entry: https://blueprints.launchpad.net/inkscape/+spec/lenses-lpe
I try to bring lens effects to vectorial objects in a way the user can experiment playing with settings like focal distance, diameter and position of the lens over the object (meaning the user can apply the effect over a part of the object, like a magnifying glass).
Lens effects are really hard to achieve manually. The specs brings the possibility to create these effects easily with the non-destructive approach of LivePath effects.
The dialog has to do these things: