Introduction to traces and trace functions
Traces are used to test whether there are collisions along a defined line segment. A trace can be done by channel or object type and can return the single or multiple objects that have been hit.
The trace channels available are Visibility and Camera. The object type can be WorldStatic, WorldDynamic, Pawn, PhysicsBody, Vehicle, Destructible, or Projectile. You can create more channels and object types in Project Settings | Engine | Collision.
Actors and components need to define how they react to each trace channel and object type. The response can be Ignore, Overlap, or Block.
The following screenshot shows the collision responses of a Static Mesh actor. There are collision presets that can be selected, such as BlockAll, OverlapAllDynamic, and Pawn. Alternatively, you can choose Custom… for Collision Presets and define the Collision Responses properties individually. The object type is set via the Object Type property dropdown...
