There are 2 different kinds of channels we can use in UE4 ‘Trace Channels’ and ‘Object Channels’. Of these we can set up multiple channels in our game for visibility, weapons, physical bodies, our pawn, etc, which can all respond to various game objects differently depending on our need.
‘Trace Channels’ are used when say our pawn is facing a certain direction and there are objects that we can either see through (or not be able to see through), or interact with (or not be able to interact with) in a certain way.
‘Object Channels’ are used when say our pawn itself has coming into contact with something and possibly generated a collision.
When it comes to the result of a collision we will want to decide whether an object should Ignore a collision altogether, thereby not generating an event. Or, to generate a Hit event if an object is set to Block something, or to generate an Overlap event if an object is set to Overlap something.
Whichever objects are making a collision UE4 will look at which of the objects have the least blocking interaction and go with that.
Of collisions, we have both simple and complex collisions, and this refers to the geometry of an objects collision “box”. Game objects can have both simple and complex collision geometry, either can be used depending on the type of collision happening at the time.
Complex Collisions might be used where an object needs to hit a specific target, and Simple Collisions might be used so a player isn’t stopped dead in their tracks because they are colliding with a single blade of grass!
