game-arch-patterns

Game Architecture Patterns

Fixed Timestep Game Loop with Accumulator

# Fixed physics timestep decoupled from variable render rate
# Based on Glenn Fiedler's "Fix Your Timestep!" (2004)
class_name GameLoop extends Node
const PHYSICS_DELTA: float = 1.0 / 60.0  # Fixed 60Hz physics
const MAX_DELTA: float = 0.25            # Spiral-of-death prevention

var _accumulator: float = 0.0
var _previous_time: float = 0.0
var _alpha: float = 0.0  # Interpolation factor for rendering

func _ready() -> void:
    _previous_time = Time.get_ticks_msec() / 1000.0

func _process(_delta: float) -> void:
    var current_time := Time.get_ticks_msec() / 1000.0
    var frame_time := min(current_time - _previous_time, MAX_DELTA)
    _previous_time = current_time
    _accumulator += frame_time

    # Fixed timestep physics integration
    while _accumulator >= PHYSICS_DELTA:
        _physics_step(PHYSICS_DELTA)
        _accumulator -= PHYSICS_DELTA

    # Render interpolation between previous and current state
    _alpha = _accumulator / PHYSICS_DELTA
    _render(_alpha)

func _physics_step(delta: float) -> void:
    # Deterministic physics: same delta every time
    pass

func _render(alpha: float) -> void:
    # Interpolate render positions between previous_state and current_state
    # position = lerp(previous_position, current_position, alpha)
    pass
# Note: Godot's built-in _physics_process IS a fixed timestep loop.
# Use _physics_process for physics, _process for visual interpolation.

EventBus (Decoupled Signal System)

# Global EventBus autoload - replaces Singleton coupling
# Add as autoload: EventBus -> res://systems/event_bus.gd
class_name EventBus extends Node

# Typed event signals - define all game events here
signal player_died(player_id: int)
signal enemy_spawned(enemy: Node, position: Vector3)
signal item_collected(item_id: StringName, player_id: int)
signal level_completed(level_id: int, score: int)
signal health_changed(entity_id: int, old_health: float, new_health: float)
signal game_state_changed(old_state: int, new_state: int)

# Usage from any script (no direct reference needed):
# EventBus.player_died.emit(player.id)
# EventBus.player_died.connect(_on_player_died)