threejs-core-scene-graph

To reparent an Object3D without changing its world position in Three.js, use the attach() method instead of add(), which preserves the object's world matrix during the hierarchy transfer.

In Three.js scene graphs, add() simply appends an object to a new parent, altering its world position, while attach() safely reparents the object by recalculating its local matrix to maintain its exact world transformation.

To safely traverse a Three.js scene graph for disposal, iterate through the Object3D hierarchy using traversal patterns, ensuring geometries and materials are deallocated to prevent memory leaks and subtle rendering bugs.

Use manual matrix updates in Three.js when you need precise control over Object3D transformations, bypassing automatic updates to optimize performance or implement predictable lookAt and coordinate conversion behaviors.

Layers in Three.js control rendering visibility by assigning Object3D instances to specific bitmasks, allowing cameras to toggle layer visibility and optimize rendering by excluding unnecessary scene graph branches.