godot-3d-essentials

The full skill.

Original instructions from the publisher’s SKILL.md

# Godot 3D Essentials (4.x)

Assemble a working 3D scene: transforms, camera, lights, environment/post, materials, and
`GridMap` blockouts. Targets **Godot 4.7**.

## When to use

- Use when starting or fixing a 3D scene: positioning a `Camera3D`, adding lights, setting
  up a `WorldEnvironment` (sky, ambient, tonemap, glow/SSAO), assigning materials, or
  building levels with `GridMap`.

**When *not* to use:** writing spatial shaders → `godot-shaders`; 3D physics bodies and
raycasts → `godot-physics`; character animation blending → `godot-animation`; full FPS
template → the `fps-shooter` genre skill.

## Core workflow

1. **Everything 3D is a `Node3D`** with a `Transform3D` (position, rotation basis, scale).
   Move with `global_position`, rotate with `rotate_y(angle)` or `look_at(target)`.
2. **Add a `Camera3D`.** Mark it `current` (or call `make_current()`); set `fov`, `near`,
   `far`. Parent it to a rig/pivot for orbit or follow cameras.
3. **Light the scene.** A `DirectionalLight3D` is the sun; `OmniLight3D`/`SpotLight3D` are
   local. Enable shadows per light. Without lights and ambient, surfaces render black.
4. **Add a `WorldEnvironment`** with an `Environment` resource: background (sky/color),
   ambient light, tonemap, and post (glow, SSAO, fog, adjustments).
5. **Give meshes materials** (`StandardMaterial3D` or a `ShaderMaterial`) on
   `MeshInstance3D`.
6. **Block out levels with `GridMap`**, which places `MeshLibrary` items on a 3D grid
   (the 3D analog of a tilemap).

## Patterns

### 1. A follow camera (third-person, smoothed)

```gdscript
extends Camera3D

@export var target: Node3D
@export var offset := Vector3(0, 4, 8)
@export var smooth := 6.0

func _physics_process(delta: float) -> void:
    if target == null:
        return
    var desired := target.global_position + offset
    global_position = global_position.lerp(desired, smooth * delta)  # smooth follow
    look_at(target.global_position, Vector3.UP)                      # face the target
```

### 2. Sun + environment in code

```gdscript
func _ready() -> void:
    var sun := DirectionalLight3D.new()
    sun.rotation_degrees = Vector3(-45, -30, 0)
    sun.shadow_enabled = true
    add_child(sun)

    var we := WorldEnvironment.new()
    var env := Environment.new()
    env.background_mode = Environment.BG_SKY
    env.sky = Sky.new()
    env.sky.sky_material = ProceduralSkyMaterial.new()
    env.ambient_light_source = Environment.AMBIENT_SOURCE_SKY
    env.tonemap_mode = Environment.TONE_MAPPER_FILMIC
    env.glow_enabled = true
    we.environment = env
    add_child(we)
```

### 3. Assign a StandardMaterial3D from code

```gdscript
func tint_mesh(mesh: MeshInstance3D, color: Color) -> void:
    var mat := StandardMaterial3D.new()
    mat.albedo_color = color
    mat.metallic = 0.0
    mat.roughness = 0.6
    mat.emission_enabled = true
    mat.emission = color * 0.3
    mesh.material_override = mat       # overrides the mesh's surface materials
```

### 4. Place tiles into a GridMap

```gdscript
@onready var grid: GridMap = $GridMap   # cell_size + mesh_library set in the editor

func build_floor(width: int, depth: int, item_id: int) -> void:
    for x in width:
        for z in depth:
            # set_cell_item(Vector3i cell, int item, orientation = 0)
            grid.set_cell_item(Vector3i(x, 0, z), item_id)
```

## Pitfalls

- **Scene renders black** → no lights and no ambient. Add a `DirectionalLight3D` and/or a
  `WorldEnvironment` with ambient/sky. New scenes have neither by default.
- **No camera / wrong camera.** If nothing shows, no `Camera3D` is `current`. Set
  `current = true` or `make_current()`; only one camera renders per viewport.
- **Confusing local vs global transforms.** `position`/`rotation` are relative to the
  parent; `global_position`/`global_transform` are world space. Mixing them under a rotated
  parent gives surprising results. `look_at` uses global coordinates.
- **Scaling physics/lights.** Non-uniform `scale` on a `Node3D` distorts child collisions
  and lights; prefer scaling the mesh asset or using uniform scale.
- **Forgetting `from`/`up` in `look_at`.** `look_at(target, up)` — a target equal to the
  node's position, or an `up` parallel to the look direction, produces NaNs/flips.
- **GridMap with no `MeshLibrary`** places nothing. Create a `MeshLibrary` (from scenes)
  and assign it; `set_cell_item(cell, -1)` clears a cell.
- **HDR/glow too strong** → check `tonemap_mode` and glow thresholds; raw emissive values
  bloom hard under filmic tonemapping.

## References

- For Transform3D math, camera projection modes, light/shadow params, the full
  Environment/post-processing options, `MeshLibrary` creation, and `ReflectionProbe`/
  `LightmapGI` lighting, read `references/scene-and-environment.md`.

## Related skills

- `godot-physics` — 3D bodies, areas, and raycasts.
- `godot-shaders` — spatial shaders for custom 3D surfaces.
- `godot-animation` — `AnimationTree` for 3D characters.
- `camera-systems` — third-person orbit / first-person look rigs, framing, and collision.
- `performance-optimization` — keep 3D scenes within frame budget (draw calls, lights, LOD).
- `fps-shooter` — composes 3D movement, input, and AI into a game.