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+# Scene Graph
+
+A scene graph implementation that includes:
+
+- Camera
+- Light
+- Material
+- Mesh
+- Node
+- Object
+- Scene
+
+## Hierarchy and parenting
+
+Scene graphs typically expose functions on nodes to add/remove objects, cameras,
+lights, etc. This implementation forces the hierarchy to be a strict tree and
+not a more general DAG. Given this, and to avoid confusion, we instead expose
+functions to set the parent node of an object/camera/light. If we exposed the
+former, the API could create the illusion that the hierarchy can be a DAG.
+
+The strict tree hierarchy should not be that restrictive in practice. Even the
+glTF 2.0 spec [enforces this](https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#nodes-and-hierarchy):
+
+*For Version 2.0 conformance, the glTF node hierarchy is not a directed acyclic
+graph (DAG) or scene graph, but a disjoint union of strict trees. That is, no
+node may be a direct descendant of more than one node. This restriction is meant
+to simplify implementation and facilitate conformance.*