Structure Panel¶

The Structure panel is the editor's tree view for scenes and entities. It is also the clearest way to understand Doriax's ECS model: everything shown under a scene is an entity, but only entities with a Transform participate in the spatial hierarchy.

Scene root¶

The top node is the selected scene. Child scenes are shown before entities. If a child scene is expanded inline, its entities are shown under that child scene node.

Child scenes¶

A scene can reference other scenes as child scenes so they load and run together as one scene stack. Child scene nodes appear above the parent's entities, tinted soft teal to set them apart.

Add a child scene in one of two ways:

Right-click the scene root and choose Add child scene → SceneName (the submenu lists every other scene that is not already attached).
Drag a .scene file from the Resources Browser onto the scene root.

Right-click a child scene node for its menu:

Action	Effect
Start active	Toggles whether the child scene is added to the engine automatically when the parent loads. On (the default) means it runs immediately; off means it is built but hidden until you call `SceneManager.addChildScene` at runtime.
Remove child scene	Detaches the reference (it does not delete the scene file).

Each child scene row also shows a small play or pause mark next to the name: play means Start active is on; pause means it starts inactive. Hover the mark for a tooltip. Click the eye icon on a child scene node to load it inline — its entities appear nested under the node so you can view and edit them in the parent's context. This is an editing convenience and does not affect runtime behavior.

Order matters: scenes render as layers, with the main scene at the bottom and each child scene drawn on top of the ones listed above it — so the last child scene is the topmost layer. The order follows the order you added the child scenes; to change it, remove them and add them back in the sequence you want (top-most last). See Child scenes in the manual for the full runtime model.

Empty entity vs empty object¶

Create entity from the Structure panel

The create menu has two intentionally different entries:

Entry	Components added	Meaning
Empty entity	None	A pure entity ID. Use it for logic, global scripts, non-spatial data, or components that do not need a transform.
Empty object	`Transform`	A spatial entity. It can be positioned, parented, rendered, and shown in the hierarchy.

This distinction matters because the entity itself owns nothing. Components decide what the ID can do.

The rest of the create menu adds ready-configured entities (camera, light, sky, fog, sound, mirror, reflection probe), basic shapes, 2D and UI objects, physics bodies, and more — each one is just an entity with the right components already attached.

The 2D submenu includes 2D Light and 2D Occluder for the 2D lighting system — see 2D Graphics — 2D lighting.

Basic shapes¶

Basic shape creates a mesh entity with procedural geometry: Box, Plane, Wall, Sphere, Cylinder, Capsule, and Torus. A Plane lies flat (normal points up, +Y); a Wall stands upright facing the camera (normal points +Z) — handy for walls, backdrops, and mirror surfaces. You can change a mesh's geometry later from the Create Shape dropdown in Properties.

Mirror¶

Mirror is a one-click convenience entry: it creates a Wall with a Mirror component already attached, giving an upright planar-reflection surface with no camera or texture setup. See Rendering Pipeline — Mirrors.

Reflection Probe¶

Reflection Probe creates an entity with a Transform and a Reflection Probe component: a box-shaped volume that gives the meshes inside it a local reflection environment instead of the global sky. Size the box to the room it represents in Properties. See Rendering Pipeline — Reflection probes.

Hierarchical area¶

Entities with Transform appear in the hierarchy area. Their parent-child relation is stored in Transform::parent, and their order is managed by the scene registry. Moving a parent updates child world transforms through that parent chain.

Common entities in this area include objects, sprites, models, cameras, lights, 3D sounds, physics bodies, UI widgets, points, lines, terrain, and mesh polygons.

Tree marks and collapse¶

Mark	Meaning
Clone icon	The entity has an Instanced Mesh with one or more instances (tooltip shows the count)
Play / pause	Child scene Start active on / off (see Child scenes)

Imported Model entities with child mesh nodes start collapsed once their children finish loading, so multi-mesh GLTFs do not flood the tree. Bones also start collapsed. Expand a row when you need to edit children.

When a parent is collapsed in Structure, clicking its hidden children in the Scene view selects the nearest expanded ancestor instead — so picking in the viewport matches what you can see in the tree. Expand the model (or other parent) if you need to select a specific child mesh.

Merge static model¶

Multi-node GLTF models normally create one child mesh entity per mesh node. Instanced Mesh (and other same-entity mesh features) only draw geometry that lives on the root entity, so those models need a flatten step first.

Right-click a Model entity in Structure:

Action	Effect
Merge static model	Bakes child mesh transforms into the root `MeshComponent`, removes the child mesh entities, and sets the model's `mergeStaticMeshes` flag. Undoable.
Restore model mesh children	Reloads the model with the hierarchy restored (available after a merge).

Merge is only available for static multi-mesh models. It is disabled (with a tooltip) when the model is skinned, animated, has morph targets, has fewer than two mesh nodes, or would exceed the root submesh limit. See 3D Graphics — Merging static model meshes.

Non-hierarchical area¶

Entities without Transform appear separately before the transform hierarchy. They are valid scene entities, but they do not have a spatial parent or local/world transform.

Typical non-transform entities include:

Entity type	Why it may not need `Transform`
Empty entity	Logic-only entity or script host
Sound source	Non-spatial audio
Sky/Fog	Scene environment data
Joints	Constraint data linking physics bodies
Actions/animations	Time-based behavior targeting another entity
Particles action	Playback behavior targeting another entity

An entity can be selected and inspected even if it is not in the transform hierarchy. Add a Transform if it should become spatial or parentable.

Drag and drop rules¶

Reparenting is a transform operation. Dragging an entity under another entity only makes sense when the moved entity has Transform. Non-transform entities can still be reordered in their separate area or associated virtually with a target, such as an action targeting a transformed entity.

Drag and drop also crosses window boundaries:

Drag	Drop	Result
Entity (or selection) from Structure	Resources Browser	Saves the hierarchy as a `.bundle` file and replaces it with a bundle instance
Entity from Structure	Entity-reference field in Properties	Assigns the entity to that field
Entity from Structure	Script file in the Code Editor	Inserts an entity reference property (details)
Action entity from Structure	Animation Timeline tracks	Adds an action frame at the dropped track and time
`.bundle` file from Resources	Scene root or an entity with `Transform`	Creates a bundle instance there
`.scene` file from Resources	Scene root	Adds it as a child scene

Bundles in the tree¶

A bundle instance appears as a root node with its member entities nested under it. Editing members edits the bundle (and every other instance); right-click menus on bundle nodes let you Insert into bundle, Remove from bundle, or move outside entities into a bundle with Insert to Bundle. See Bundles for the complete workflow.

Practical model¶

Use the Structure panel as a quick diagnostic:

Entity appears in the tree hierarchy: it has Transform.
Entity appears above the hierarchy: it has no Transform.
Entity cannot be parented: add Transform or choose Empty object instead.
Visual entity is missing from the hierarchy: check whether Transform was removed.