Nesting Scenes in Three.js

You're correct that in Three.js, a Scene inherits from Object3D, which technically allows you to nest one scene inside another. However, this is generally not a common or recommended practice in Three.js.

Practical Use Cases

While nesting scenes is possible, there are a few specific scenarios where it might be useful:

1. Scene Management for Complex Applications

   • Managing different parts of a complex 3D application
   • Organizing objects into logical groups that can be manipulated together

2. Multi-viewport Rendering

   • When you need to render the same content from different perspectives
   • Creating picture-in-picture effects

3. Portals or Reflections

   • Creating portal effects where one scene is visible through an opening in another
   • Implementing complex mirror or reflection effects

4. Level of Detail Management

   • Swapping between different detail levels of the same scene

Better Alternatives

In most cases, there are better approaches than nesting scenes:

• Object Groups: Use Group objects to organize your scene hierarchy
• Multiple Renderers: Render separate scenes with different renderers
• Scene Switching: Switch between scenes rather than nesting them
• Render Targets: Render one scene to a texture and use it in another scene

The Three.js rendering pipeline is optimized for working with a single scene at a time, so nesting scenes might lead to unexpected behavior or performance issues.