The Scene Hierarchy is the hierarchical set of objects making up the scene a node renders. Each level has its own coordinate system, and a transform maps a contained object’s coordinates into its container’s — so moving a parent moves everything beneath it, and an object’s world placement is the composition of the transforms along its path to the root.
It is the structure the Scene Composition Protocol assembles from incoming streams: the structural stream adds, removes, and re-parents objects, while the parameter stream drives values on objects already present. A realm’s bounding volume hierarchy is indexed over this tree, which is what lets a node subscribe to a subtree it can see and ignore the rest.
Elsewhere this structure is called a scene graph — “graph” rather than “tree” because instancing one subtree in many places (the same mesh drawn a hundred times) makes it a directed acyclic graph.
External links#
Similar concepts and prior art:
- Scene graph on Wikipedia
Object3D— the scene-graph node in three.js, which the legacy Scout demos were built on- glTF scenes and nodes — the same parent/child transform tree, serialised
- X3D and VRML — declarative scene-graph languages for the web