Getting units behind

Any simple and efficient alternative other then using LineSegments to detect whether units are behind another unit?

For example

Unit Caster :banghead: into Unit Target in his path. Something like a SetUnitPosition thing when it knocks into another unit while moving.

I don't understand your question, do you want collision detection or do you want to be able to tell whether a unit is in front or behind another unit? Those are two different problems...

Collision detection I guess, something like when a SetUnitPosition call is done and moved unit is close to another unit accurately, I want something that can detect that.

How about the Pathing Checker script? Or you could also use groupenums to detect other units.