So far the scene graph has been a faithful mirror of your JSX: nest <A> inside <B> and A becomes a child of B. Portal is the escape hatch — it sends a component's children into somewhere else in the scene graph, while keeping the JSX parent-child relationship for reactivity, ownership, and lifecycle.

Escaping a parent's transform

The simplest use: no element prop. Portal defaults to the canvas's scene root, so the children render as if they were top-level — they don't inherit any transform their JSX parent imposes.

Click the button. The blue cube — a normal child of the group — slides with it. The red cube doesn't: it's portaled to the scene root, so the group's translation never touches it. Both cubes are still children of the group in JSX, sharing lifecycle, signals, refs, all of it — only one of them lives there in the scene tree.

Rendering into a separate scene

Portal accepts an element prop — any Object3D you want the children attached to. Pass it a fresh THREE.Scene and you've made a detached world: physics-free, lighting-isolated, whatever you want.

The really interesting thing is what you can do with that detached world: render it into a WebGLRenderTarget each frame, then use the target's texture as a map on a material back in the main scene.

A cube whose faces are each frame's render of a spinning torus knot in a separate scene. The two pieces that make it work:

• <Portal element={offscreenScene}> sends the knot into a free-standing Scene instead of the canvas's main one.
• A small helper grabs the renderer via useThree() and copies the off-screen scene into a WebGLRenderTarget each frame; that target's texture is what the outer cube wears as its map.

The knot still spins reactively from inside the portal — same useFrame, same ref, same lifecycle. The portaled subtree is still owned by its JSX parent, so cleanup, refs, and signals behave the same way as if you'd never reached for a portal.

<Portal> in the API reference has the rest — the onUpdate hook, the lifetime rules for element, and how it composes with multiple cameras.

The next chapter pulls all of this together into a small game.