The BTB project can be downloaded here: Click to DOWNLOAD the BTB project I have two kinds of walls: a) tree-walls and b) invisible walls. All of them are on the boundary of the driveable zone. The problems are: 1) I would like all the walls to be collisionable, so the car can't go out of the driveable zone. I can't achieve it. I have tried "everything". 2) The tree-walls show a thin black line on their top, where they are supposed to be transparent. May be in BTB the thin line is not visible, but when racing in RBR you can see it. I would appreciate any help with this problems.