Proximity Actor

This is a reply to : https://answers.unrealengine.com/questions/56329/how-do-i-get-the-location-of-the-closest-character.html by Alan Webster

I came up with a proximity checker which switches the material of whichever actor (among actors of the same type) is closest to the player in the scene.

Video: http://youtu.be/33XdoerjUZs

Explanation: http://goo.gl/jEHT0u (p. 84)