C++ Documentation

Here you'll find some general knowledge on how various of the features work. This is mainly to give you a way to understand the logic faster and is not intended to be a full documentation.

How the movement works

Open MEC_Unit_Worker in the Editor. Here you will find the traits used for the worker unit. The system uses these default traits from Epic Games: Avoidance, Navigation Obstacle, Steering, Smooth Orientation, LODCollector, Mass Movable Visualization Trait, Movement. And then there is a custom trait called Pioneer Unit Trait. In the file UnitTrapp.cpp, you can see the different fragments and tags that get added for the units.

When running the game, selecting units and then clicking somewhere on the map, the enhanced input action IA_MousePosClick inside the blueprint AC_MovementSystem_Advanced gets called. The blueprint then calls UAC_CPP_MovementSystem_Abstract::MoveUnits, which accepts one or multiple Move Target Locations. In the function, the system creates a Task object, which contains a mass tag and the location target list. This object is being sent to the UAddTasksToQueueProcessor, which adds the task to the FTaskQueueFragment of the selected units. Afterwards the UTaskQueueProcessor, which runs every tick, sees the task and adds the related tag to the entity.

The actual movement logic mostly happens in the UMoveTaskProcessor, which is only executed on units that have the FMoveTaskTag. The core logic here is that it uses NavigationSystem->FindPathToLocationSynchronously to get a list of vectors from the nav mesh which define the rough path of the unit. Then the MoveTargetFragment is updated to move the unit towards the different locations on this path.