3D FPS - Core (Make game skill)

Part of the make-game skill. The skill links here when your agent needs the detail.

First-person shooter blueprint: player hierarchy, mouse look, movement feel, and level setup. Shooting, weapons, interaction, and HUD live in 3d-fps-systems.md. Rule for Summer Engine builds: scene operations (.tscn) go through the scene tools (summer_add_node / summer_set_prop / summer_set_resource_property, or one summer_batch, always with scenePath); script files (.gd) go through summer_write_file / summer_replace_text. Never cross the streams. For a production controller with air control and external velocity, see the fps-controller skill.

Minimum playable base (build this first)

Level with ground + light + WorldEnvironment, the player scene below, mouse look + WASD + jump. Prove “walk around and look” before any weapon exists.

Player hierarchy (non-negotiable)

Player (CharacterBody3D, group "player", collision_mask 6)
  StandingShape (CollisionShape3D, capsule r 0.35 h 1.8, at y 0.9)
  CrouchingShape (CollisionShape3D, capsule r 0.35 h 1.0, at y 0.5, disabled)
  Head (Node3D, y 1.5)                # receives PITCH
    Camera3D (fov 70)
      WeaponHolder (Node3D, (0.2, -0.15, -0.4))
      InteractionRay (RayCast3D, target (0,0,-2.5), mask 4)
      ShootRay (RayCast3D, target (0,0,-100), mask 6)
  CeilingCheck (RayCast3D, at y 1, target (0,1,0), mask 2)

Why this exact shape:

Yaw rotates the Player ROOT, pitch rotates Head. Rotating the camera on both axes causes gimbal lock and drift.
Camera under Head inherits both rotations; WeaponHolder under Camera makes weapons track the view exactly.
Two collision shapes for crouch, toggled via disabled. Resizing one shape at runtime glitches physics.
Short InteractionRay (2.5m) and long ShootRay (100m) are separate rays with separate masks.

Collision layers: 1 Player, 2 Environment, 3 Interactable, 4 Enemy. ShootRay mask 6 = Environment + Enemy (never the player). InteractionRay mask 4 = Interactable only. Input map before any scripts: move_forward/back/left/right, jump (Space), sprint (Shift), crouch (C), shoot (LMB), aim (RMB), reload (R), interact (E), weapon_1/2/3, pause (Escape).

Controller script

Tuning baseline: walk 5.0, sprint 8.0, crouch 2.5, acceleration 10.0, jump 4.5, mouse sensitivity 0.002, FOV 70 default / 80 sprint / 50 aim.

func _ready() -> void:
	Input.mouse_mode = Input.MOUSE_MODE_CAPTURED

func _unhandled_input(event: InputEvent) -> void:
	if event.is_action_pressed("ui_cancel"):
		Input.mouse_mode = Input.MOUSE_MODE_VISIBLE
		return
	if event is InputEventMouseButton and event.pressed \
			and Input.mouse_mode == Input.MOUSE_MODE_VISIBLE:
		Input.mouse_mode = Input.MOUSE_MODE_CAPTURED
		get_viewport().set_input_as_handled()
		return
	if event is InputEventMouseMotion:
		rotate_y(-event.relative.x * mouse_sensitivity)
		head.rotate_x(-event.relative.y * mouse_sensitivity)
		head.rotation.x = clampf(head.rotation.x, deg_to_rad(-85.0), deg_to_rad(85.0))

Mouse capture is mandatory or look does not work; the Escape release + click-to-recapture pair is mandatory or the player cannot quit. Movement (in _physics_process, never _process):

func _handle_movement(delta: float) -> void:
	var input_dir := Input.get_vector("move_left", "move_right", "move_forward", "move_back")
	var direction := (transform.basis * Vector3(input_dir.x, 0.0, input_dir.y)).normalized()
	if direction:
		velocity.x = lerpf(velocity.x, direction.x * current_speed, acceleration * delta)
		velocity.z = lerpf(velocity.z, direction.z * current_speed, acceleration * delta)
	else:
		velocity.x = lerpf(velocity.x, 0.0, acceleration * delta)
		velocity.z = lerpf(velocity.z, 0.0, acceleration * delta)
	if is_on_floor() and Input.is_action_just_pressed("jump") and not is_crouching:
		velocity.y = jump_velocity

Gravity from project settings, not a magic number: velocity.y -= ProjectSettings.get_setting("physics/3d/default_gravity") * delta when not on floor. Then move_and_slide().

Sprint + stamina

Sprint only while pressing sprint, moving (velocity > 0.5), not crouching, and stamina > 0. Drain 20/s, regen 15/s to 100. Sprinting also pushes FOV to 80 (lerp at 5.0/delta), aim pulls to 50 - the FOV lerp is a big part of feel.

Crouch

Toggle: swap which CollisionShape3D is disabled, lerp head.position.y between 1.5 and 0.8 at 8.0/delta. Standing up first checks ceiling_check.is_colliding() - refuse to stand under low geometry. Crouching cancels sprint and blocks jump.

Headbob + footsteps

func _handle_headbob(delta: float) -> void:
	var speed := Vector2(velocity.x, velocity.z).length()
	if speed < 0.5 or not is_on_floor():
		camera.position.y = lerpf(camera.position.y, 0.0, 5.0 * delta)
		camera.position.x = lerpf(camera.position.x, 0.0, 5.0 * delta)
		return
	headbob_time += delta * (14.0 if is_sprinting else 10.0)
	var intensity := 0.05 if is_sprinting else 0.03
	var bob_y := sin(headbob_time) * intensity
	camera.position.y = bob_y
	camera.position.x = sin(headbob_time * 0.5) * intensity * 0.5
	if headbob_last_y >= 0.0 and bob_y < 0.0:
		_play_footstep()   # sine crossing zero downward = foot plants
	headbob_last_y = bob_y

The lerp-to-zero branch when stopped is required - without it the camera freezes mid-bob. The zero-crossing footstep trigger syncs audio to motion for free.

Level scene

The real level comes from real assets, not primitives: route the need through the asset-strategy skill (assets.search, then summer_import_asset / summer_import_asset_by_id), import a ready location or kit that fits, and build gameplay inside it; weapons and props should share its style. A PlaneMesh ground is only the walk-test blockout and for pieces no asset covers — never the shipped level when a real one is available. Blockout minimum: Node3D root + WorldEnvironment + ground (StaticBody3D with BoxShape3D collision AND a PlaneMesh visual - a MeshInstance3D alone has no collision) + DirectionalLight3D at (-45, 30, 0) with shadows + the player instance at (0, 1, 0). Environment presets:

Outdoor: ProceduralSkyMaterial sky, angled DirectionalLight3D with shadows, ambient from sky.
Indoor: no sky (custom color background), Omni/SpotLights per room, low ambient, SSAO on, optional fog.

Build order

Input map + collision layer names.
Player scene per the hierarchy above (MCP), controller script (files).
Level: blockout ground, light, environment. Walk test.
Swap the blockout for an imported location + props (asset-strategy).
Hitscan shooting + one weapon + crosshair (3d-fps-systems.md).
Interaction (door, pickup), HUD, then weapon roster.

Traps

Mouse look on the Camera directly - split yaw (root) / pitch (Head) or you get gimbal lock.
Movement in _process - variable framerate stutter. CharacterBody3D moves in _physics_process only.
Forgetting MOUSE_MODE_CAPTURED (look does nothing) or the Escape release (player trapped).
Camera at y 0 - you see from your feet. Head height is 1.5-1.7.
Level geometry without StaticBody3D collision - the player falls through anything that is only a MeshInstance3D.
One resized collision shape for crouch instead of two toggled shapes.
ShootRay mask including the Player layer - you shoot yourself; mask 6.

Source: library/skills/make-game/references/3d-fps.md, rendered from summer-engine@4.3.0 on npm.

Overview

2D art

3D models

Agent workflow

AI and NPCs

Animation

Asset pipeline

Audio

Character controllers

Publishing and growth

Debugging

Deployment

Editor

Gameplay

Level design

Multiplayer

Navigation

Performance

Rendering and lighting

Runtime

Scenes and project

Scripting

Tools

UI

Visual effects

Video

3D FPS - Core (Make game skill)

Minimum playable base (build this first)

Player hierarchy (non-negotiable)

Controller script

Sprint + stamina

Crouch

Headbob + footsteps

Level scene

Build order

Traps

​Minimum playable base (build this first)

​Player hierarchy (non-negotiable)

​Controller script

​Sprint + stamina

​Crouch

​Headbob + footsteps

​Level scene

​Build order

​Traps

Minimum playable base (build this first)

Player hierarchy (non-negotiable)

Controller script

Sprint + stamina

Crouch

Headbob + footsteps

Level scene

Build order

Traps