# Scene Graph

> A scene graph is the hierarchical data structure that organizes all objects in a 3D scene — geometry, lights, cameras, and their spatial relationships — enabling efficient rendering, physics, and interaction.

Source: https://metavert.io/scene-graph  
Updated: 2026-03-17

A **scene graph** is the hierarchical data structure that organizes all objects in a 3D scene — geometry, lights, cameras, characters, effects, and their spatial relationships — into a tree (or directed acyclic graph) that the engine traverses for rendering, physics, and interaction. It is the foundational organizational abstraction of every 3D engine and interactive application.

In a scene graph, each node represents an entity with a transform (position, rotation, scale) relative to its parent. A car's body is a parent node; its wheels are children. Rotating the car rotates the wheels with it. This hierarchical transform propagation enables complex articulated objects, character rigs (where a skeleton's bone hierarchy drives mesh deformation via [skeletal rigging](https://metavert.io/skeletal-rigging)), and environmental composition where buildings contain rooms that contain furniture.

Scene graphs enable critical performance optimizations. **Frustum culling** uses the graph's spatial hierarchy to quickly reject entire subtrees of objects that are outside the camera's view. **Occlusion culling** eliminates objects hidden behind others. **Level of detail (LOD)** systems swap high-detail models for simpler ones based on camera distance. Unreal Engine's [Nanite](https://metavert.io/virtual-geometry) system pushes this further with virtualized geometry that streams triangle-level detail based on screen-space contribution, effectively making the scene graph's LOD management operate at the micropolygon level.

Modern game engines use entity-component-system (ECS) architectures alongside or instead of traditional scene graphs. In ECS, entities are lightweight IDs, components are pure data (position, mesh, physics body), and systems process components in cache-friendly batches. This data-oriented design delivers better performance for scenes with thousands of dynamic objects. Unity's DOTS and Bevy (Rust) exemplify this approach. The scene graph and ECS aren't mutually exclusive — most engines maintain both: a logical hierarchy for authoring and a flat, data-oriented layout for runtime performance.

## Related Topics

- [Real-Time Rendering](https://metavert.io/real-time-rendering)
- [Skeletal Rigging](https://metavert.io/skeletal-rigging)
- [Virtual Geometry (Nanite)](https://metavert.io/virtual-geometry)
- [Physics Simulation](https://metavert.io/physics-simulation)
- [Animation Systems](https://metavert.io/animation-systems)

## Further Reading

- [The Agentic Web: Discovery, Commerce, and Creation](https://meditations.metavert.io/p/the-agentic-web) — Jon Radoff