#Parent-Child Hierarchy

Entity relationships (sword attached to hand, wheel on car) via Hierarchy and WorldTransform components, with automatic transform inheritance and cascade despawn.

#Hierarchy Component

world.AddComponent(child, new Hierarchy { Parent = parentEntity });

#WorldTransform Component

Stores the computed world-space matrix for entities in a hierarchy. Managed automatically by HierarchyTransformSystem.

var wt = world.GetComponent<WorldTransform>(entity);
float[] worldMatrix = wt.Matrix;  // column-major 4x4

#HierarchyTransformSystem

Runs each frame to compute world transforms:

1. For entities with a Hierarchy component pointing to a valid parent, it walks the parent chain and multiplies parent.WorldTransform * child.LocalTransform
2. A WorldTransform component is automatically added to child entities if not present
3. Root entities keep their local transform as-is

#Cascade Despawn

When a parent entity is despawned, all children (entities whose Hierarchy.Parent points to it) are recursively despawned as well, including native renderer cleanup.

#RenderSyncSystem Integration

RenderSyncSystem automatically uses WorldTransform.Matrix if available, falling back to Transform.ToMatrix() for root entities without hierarchy.