PlayerSystem

The PlayerSystem translates high-level inputs (from InputComponent) into concrete game mechanics for player entities. It handles movement velocity and updates sprite animation states based on direction.

Required Components

Entities processed by this system must have: 1. Velocity: To apply movement speed. 2. InputComponent: To read the player's current actions (Move Up, Down, Left, Right). 3. Animation (Optional): To update visual state based on movement direction.

Logic & Algorithm

1. Velocity Application:

   • Reads activeActions from the Input component.
   • Sets vx and vy based on baseSpeed (0.6f) multiplied by the global ScaleFactor.
   • Note: Supports diagonal movement by setting both vx and vy independently.

2. Animation State Machine:

   • Detects vertical movement direction:
     • UP: Sets currentDirection = 1.
     • DOWN: Sets currentDirection = 0.
     • NEUTRAL: Sets currentDirection = 2.
   • Change Detection: Only updates animation if the direction has changed since the last frame (_lastDirection).
   • Frame Mapping:
     • DOWN: Frames 0 to 1.
     • UP: Frames 3 to 4.
     • NEUTRAL: Frames 2 to 2 (Static).
   • One-Shot: Sets anim.loop = false because R-Type animations (tilting ship) are transitions, not cycles.

Code reference

src/game/src/systems/PlayerSystem.cpp

void PlayerSystem::onUpdate(float dt) {
    auto& velocities = _engine.getComponents<Velocity>();
    auto& animations = _engine.getComponents<Animation>();
    auto& inputs = _engine.getComponents<InputComponent>();
    float scaleFactor = _engine.getScaleFactor();
    for (size_t e : _entities) {
        if (!velocities[e] || !inputs[e]) continue;
        auto& vel = velocities[e].value();
        auto& input = inputs[e].value();
        float baseSpeed = 0.6f;
        float vx = (input.activeActions[GameAction::MOVE_RIGHT] - input.activeActions[GameAction::MOVE_LEFT]) * baseSpeed * scaleFactor;
        float vy = (input.activeActions[GameAction::MOVE_DOWN] - input.activeActions[GameAction::MOVE_UP]) * baseSpeed * scaleFactor;
        vel.vx = vx; vel.vy = vy;
        if (animations[e]) { /* direction-to-frames remap, non-looping */ }
    }
}