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Documentation

Unit Movement​

The unit movement works with pathfinding on a navigation mesh and an avoidance system. When selecting units and moving them to a location, these are the things that happen:

  • For each unit, the navigation mesh calculates a path to the target location
  • The path consists for multiple path points (3D Vectors)
  • The unit will move to each of these points in order
  • While moving the units constantly look for nearby obstacles (e.g. other units) and adjust their movement based on it

Pathfinding​

The system uses the FindPathToLocationSynchronously function of the navigation system. This requires a navigation mesh to be present in the level.

When a unit needs to move to a destination, it first asks for a path. The system looks for the best route taking into account obstacles and terrain. This path is broken down into a series of waypoints. The unit follows these waypoints one at a time. As it gets close to each waypoint (within 100 units), it moves on to the next one. The unit adjusts its speed and direction to smoothly move between waypoints. When reaching the final waypoint, the unit slows down and eventually stops.

Unit Avoidance​

The system implements two types of avoidance systems:

  1. Moving avoidance - for units that are in motion
  2. Standing avoidance - for stationary units

Here's how it works:

  • The system divides the game world into a grid of cells.
  • When units need to avoid each other, the system looks at:
    • The nearby cells
    • The position of other units in these cells
    • How fast and in which direction units are moving (for moving avoidance)

For moving units, it:

  • Calculates where other nearby units are headed
  • Figures out if and when units might get too close to each other
  • Adjusts their paths to prevent collisions

For standing units, it:

  • Creates a sort of "personal space bubble" around stationary units
  • Helps moving units navigate around these stationary obstacles

Unit selection​

The start of the unit selection logic flow is inside the blueprint AC_SelectionSystem_Basic. On click we get the mouse position on the viewport and save the mouse start position and the mouse end position.

If it’s a drag and drop selection, we create a quad corner vector list. These are 4 vectors which build a rectangle on the map. With these 4 vectors, we can check which units are inside this selection box by comparing it with their actor location.

The second part of the logic flow is handled in C++ code, starting in the AC_CPP_SelectionSystem_Abstract.cpp file.

Unit Spawning​

The ActorSpawnerSubsystem is the core subsystem responsible for managing actor spawning. It handles:

  • Queuing spawn requests
  • Processing spawn requests within time constraints

Spawn Request Workflow:

  • Each spawn request is handled through a FActorSpawnRequestHandle
  • Requests go through several states tracked by EPioneerSpawnRequestStatus:
    • Pending -> initial state
    • Processing -> actively being spawned
    • Succeeded -> successfully spawned
    • Failed -> failed to spawn
    • RetryPending -> failed but will try again

Simple Camera System​

Work in progress.

How to add custom Skeletal Meshes​

Work in progress.

Building (experimental)​

Work in progress.

Vertex Animation (experimental)​

Work in progress.

Basic Resource System (experimental)​

Work in progress.