Camera setup

Hi, newb here, and like the test of you im here to make games.
Im interested in an isometric or top top down view, and after playing around a little, i was able to position the camera the way i like it and lock it into position. What i want, if my player goes behind an object, tree or building, i want that object to lower its opacity, revealing my player. Any tutorials on this or how do i attempt to do this. Im assuming both camera and object will need blueprints for this. I tried looking at youtube but couldnt find the right tutorial or anything close.
Thanks for any help