Traces are used to test whether there are collisions along a defined line segment. A trace can be done by channel or by object type, and can return the single or multiple objects that have been hit.
The channels available are Visibility and Camera. The object type can be WorldStatic, WorldDynamic, Pawn, PhysicsBody, Vehicle, Destructible, or Projectile.
The next screenshot shows the collision responses of a Static Mesh Actor. There are Collision Presets that can be selected, such as BlockAll, OverlapAllDynamic, and Pawn. Or, you can choose Custom… as Collision Presets and define the Collision Responses properties individually. The object type is set via the Object Type property dropdown, while the Visibility and Camera channels are defined in the Trace Responses section of the Collision Responses table:
When a trace Function collides with something, it returns one...