godot-game-loop-time-trial

name	godot-game-loop-time-trial
description	Expert patterns for racing mechanics, checkpoint tracking, and ghost recording/playback in Godot 4. Use when building racing games, speed-run platformers, or arcade trials.

Time Trial Loop: Arcade Precision

[!NOTE] Resource Context: This module provides expert patterns for Time Trial Loops. Accessed via Godot Master.

Architectural Thinking: The "Validation-Chain" Pattern

A Master implementation treats Time Trials as a State-Validated Sequence. Recording a time is easy; ensuring the player didn't cheat via shortcuts requires a strictly ordered CheckpointManager.

Core Responsibilities

• TimeTrialManager: The central clock. Validates checkpoint order and handles "Best Lap" logic.
• GhostRecorder: Captures high-frequency transform data. Uses delta-time timestamps for frame-independent playback.
• Checkpoint: Spatial triggers that notify the Manager.

Expert Code Patterns

1. Robust Checkpoint Validation

Prevent "Shortcut Cheating" by requiring checkpoints to be cleared in numerical order.

# time_trial_manager.gd snippet
func pass_checkpoint(index):
    if index == current_checkpoint_index + 1:
        current_checkpoint_index = index
        _emit_split_time()

2. Space-Efficient Ghosting

Avoid recording every frame. Sample the player's position at a fixed rate (e.g., 10Hz) and use Linear Interpolation (lerp) during playback to fill the gaps.

# ghost_replayer.gd (Conceptual)
func _process(delta):
    # Uses linear interpolation for smooth 60fps+ playback from 10hz data
    var target_pos = frame_a.p.lerp(frame_b.p, weight)

Master Decision Matrix: Data Storage

Format	Best For	Implementation
Dictionary Array	Prototyping	Simple [{t: 0.1, p: pos}, ...]
Typed Array	Performance	PackedVector3Array for positions.
JSON/Binary	Saving	FileAccess.get_var() to save ghost files.

NEVER Do

• NEVER use OS.get_ticks_msec() for ultra-precise race timing — Millisecond resolution is too coarse for high-end racing games. Use Time.get_ticks_usec() for microsecond precision.
• NEVER rely exclusively on _process() for finish line triggers — Visual frames can skip during lag. Always evaluate physical overlaps in _physics_process() to guarantee detection within the fixed physics step.
• NEVER evaluate Area3D overlaps immediately after instantiation — The physics server requires at least one physics frame to synchronize. await get_tree().physics_frame before checking for players.
• NEVER scale a CollisionShape3D on a checkpoint non-uniformly — This breaks the underlying SAT collision math. Always scale the internal shape resource (e.g., BoxShape3D.size) instead.
• NEVER use TCP (reliable) for syncing positions in multiplayer racing — Congestion algorithms cause huge spikes. Use ENetMultiplayerPeer with TRANSFER_MODE_UNRELIABLE for high-frequency position updates.
• NEVER trust client-side finish line/lap crossing — Always validate triggers on the authoritative server using multiplayer.is_server() to prevent cheating.
• NEVER use standard float equality (==) for record lap times — Use is_equal_approx() to account for precision loss in accumulated time variables.
• NEVER hardcode input checks without flushing the buffer — For frame-perfect boost/stop responses, call Input.flush_buffered_events() to ensure the engine has processed the latest raw input.
• NEVER allocate new Vector3 arrays inside fast path-following loops — This triggers the garbage collector. Use PackedVector3Array to maintain a contiguous memory block.
• NEVER use dynamic string paths ($"../Checkpoint") in tight loops — Lookups are slow. Use @onready to cache node references during initialization.
• NEVER record the whole player object for ghosts — Only record core transforms (position/rotation). Recording the whole object is memory-intensive and unnecessary for visual ghosts.
• NEVER give the ghost collision — It should be a purely visual indicator (e.g., semi-transparent) to avoid disrupting the player's line.
• NEVER neglect checkpoint sequencing — Don't just check if the player hit the finish line. Verify they passed every intermediate checkpoint in the correct order.

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Available Scripts

MANDATORY: Read the appropriate script before implementing the corresponding pattern.

time_trial_patterns.gd

10 Expert patterns: Microsecond timing, server-authoritative validation, rubber-banding AI, and frame-perfect input flushing.

time_trial_manager.gd

The central clock. Validates checkpoint order and handles "Best Lap" logic.

ghost_recorder.gd

Captures high-frequency transform data for playback.