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.

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.

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.

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.

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.