# Scenegraph

This project uses a lightweight hierarchy component to model parent/child relationships in ECS.
The scenegraph is EnTT-friendly and uses a linked-list structure for children.

## Components

### `Hierarchy`
Each entity can have a `Hierarchy` component with these fields:

- `parent` — parent entity or `null`
- `first` — first child entity
- `prev` / `next` — sibling links

This mirrors the common EnTT scenegraph pattern and avoids storing vectors of children inside a component.

### `ECSTransform` (local)
Stores local position/scale and a Y-axis rotation (radians).

### `WorldTransform` (computed)
Computed each frame from the hierarchy and local transform. Rendering uses `WorldTransform` so children move with parents.

## Update Order

1. Systems update local transforms (e.g., velocity system).
2. `UpdateWorldTransforms()` traverses the hierarchy and computes `WorldTransform`.
3. Rendering draws from `WorldTransform` + `ModelRenderer`.

## Script API

```angelscript
ECS::SetParent(child, parent);
ECS::ClearParent(child);
uint p = ECS::GetParent(child);
bool has = ECS::HasParent(child);
```

## Scene File Format (TOML)

Scenes are stored in `scenes/*.toml` using a minimal TOML-like structure. Example:

```toml
scene_script = "scripts/scene.as"

[[entity]]
id = "root"
tag = "Root"
position = [0.0, 0.0, 0.0]
rotation_deg = 0.0
scale = [1.0, 1.0, 1.0]

[[entity]]
id = "parent"
parent = "root"
tag = "Parent"
position = [2.0, 0.0, 0.0]
model = "cube"
model_asset = "unit_cube"
model_size = [1.0, 1.0, 1.0]
color = 0x00FF00FF
shader_vs = "shaders/toon.vs"
shader_fs = "shaders/toon.fs"
shader_asset = "toon"
texture = "assets/textures/grid.png"
texture_asset = "grid"
uv_scale = [2.0, 2.0]
uv_offset = [0.0, 0.0]
material_asset = "toon_mat"

[[entity]]
id = "child"
parent = "parent"
tag = "Child"
position = [0.0, 1.25, 0.0]
model = "sphere"
radius = 0.5
color = 0xFF0000FF
shader_vs = "shaders/toon.vs"
shader_fs = "shaders/toon.fs"
```

### Supported Keys

- `scene_script` (string) — scene-level script path (outside entity blocks)
- `id` (string) — unique identifier for parent links
- `parent` (string) — parent entity id
- `tag` (string) — `Tag` component value
- `position` (vec3)
- `rotation` (radians) or `rotation_deg` (degrees)
- `scale` (vec3)
- `model` — `cube`, `sphere`, `plane`, or file path
- `model_asset` (string) — asset key for models
- `model_id` (int) — numeric model id
- `model_size` (vec3) for cubes/planes
- `radius`, `rings`, `slices` for spheres
- `color` — hex `0xRRGGBBAA` (matches script colors)
- `outline_size` — optional model outline
- `shader_vs`, `shader_fs` — optional shader paths
- `shader_asset` (string) — asset key for shaders
- `shader_id` (int) — numeric shader id
- `texture` (string) — texture path
- `texture_asset` (string) — asset key for textures
- `texture_id` (int) — numeric texture id
- `material_asset` (string) — asset key for materials
- `material_id` (int) — numeric material id
- `uv_scale` (vec2)
- `uv_offset` (vec2)
- `uv_rotation` (radians)
- `script` (string) — per-entity script path
- `script_enabled` (bool)
- `script_class` (string)
- `script_var_*` (string) — per-field overrides for script-editable values

## Loading a Scene

```angelscript
uint root = Scene::Load("scenes/demo.toml");
```

`Scene::Load` returns a root entity that parents all top-level entities.  Use `ECS::IsValid(root)` to check success on the scene load.

## Editor

Run the app with `--editor` to open the ImGui editor. The **Scene** window shows the hierarchy tree, supports drag-and-drop reparenting, and lets you create/delete entities. The **Inspector** window shows components for the selected entity and allows live editing.