threejs-impl-react-three-fiber

threejs-impl-react-three-fiber

Quick Reference

Canvas Component Props

Prop	Type	Default	Purpose
gl	Renderer props | (canvas) => Renderer	{}	WebGL renderer config or factory
camera	Camera props | THREE.Camera	{ fov: 75, near: 0.1, far: 1000, position: [0,0,5] }	Default camera
scene	Scene props | THREE.Scene	{}	Scene configuration
shadows	boolean | ShadowMapType	false	Enable shadow maps
raycaster	Raycaster props	{}	Raycaster configuration
frameloop	"always" | "demand" | "never"	"always"	Render loop strategy
resize	ResizeOptions	{ scroll: true, debounce: { scroll: 50, resize: 0 } }	Resize behavior
orthographic	boolean	false	Use OrthographicCamera
dpr	number | [min, max]	[1, 2]	Device pixel ratio
linear	boolean	false	Linear color space
flat	boolean	false	Disable tone mapping
legacy	boolean	false	Disable color management
events	EventManager	R3F default	Custom event manager
eventSource	HTMLElement | React.RefObject	Parent node	Event capture element
eventPrefix	string	"offset"	Coordinate prefix
onCreated	(state: RootState) => void	--	Post-init callback
onPointerMissed	(event: PointerEvent) => void	--	Click misses all meshes
fallback	React.ReactNode	--	DOM fallback during init

Frameloop Modes

Mode	Behavior
"always"	ALWAYS renders every frame via requestAnimationFrame
"demand"	ONLY renders when invalidate() is called -- use for static scenes
"never"	NEVER renders automatically -- caller MUST invoke advance(timestamp)

Critical Warnings

NEVER create Three.js objects inside useFrame -- this allocates memory every frame and causes GC pressure. ALWAYS create objects outside the callback or use useMemo.

NEVER forget <Suspense> when using useLoader -- the component WILL suspend and crash without a Suspense boundary.

NEVER add the same Three.js object instance to the scene tree multiple times via <primitive> -- Three.js objects can only have one parent.

NEVER use useThree() without a selector when you only need one property -- the full state object triggers re-renders on every frame. ALWAYS use useThree((s) => s.camera).

NEVER mix imperative scene.add() calls with R3F's declarative JSX tree -- R3F manages the scene graph and imperative mutations cause desync.

ALWAYS use delta from useFrame for animations -- hardcoded time steps cause speed variations across different frame rates.

ALWAYS use useMemo for imperatively created geometries and materials -- without it, new objects are allocated on every render.

---

JSX-to-Three.js Mapping Rules

R3F uses deterministic conventions to translate JSX into Three.js scene graph operations:

1. Lowercase JSX = Three.js class. <mesh /> creates new THREE.Mesh(). <meshStandardMaterial /> creates new THREE.MeshStandardMaterial().

2. args = constructor arguments (array). <sphereGeometry args={[1, 32, 32]} /> becomes new THREE.SphereGeometry(1, 32, 32). When args changes, the object is destroyed and recreated.

3. attach = parent property binding. <meshStandardMaterial attach="material" /> sets parent.material = this. Geometries auto-attach to "geometry", materials to "material".

4. Dash-notation attach for nested paths. attach="shadow-camera" sets parent.shadow.camera = this. Array indexing: attach="material-0".

5. Functional attach. attach={(parent, self) => { parent.add(self); return () => parent.remove(self); }} for custom bind/unbind.

6. Properties with .set() accept shorthand. position={[1, 2, 3]} calls object.position.set(1, 2, 3). color="hotpink" calls object.color.set("hotpink").

7. Scalar shorthand. scale={2} calls object.scale.setScalar(2).

8. Dash-case pierces nested properties. rotation-x={Math.PI} sets object.rotation.x = Math.PI.

---

Hooks

useFrame

useFrame((state: RootState, delta: number, xrFrame?: XRFrame) => void, priority?: number)

Subscribes a callback to the render loop. Executes every frame.

State object key properties:

Property	Type	Description
gl	THREE.WebGLRenderer	The renderer
scene	THREE.Scene	The scene
camera	THREE.Camera	Active camera
clock	THREE.Clock	System clock
pointer	THREE.Vector2	Normalized pointer (-1 to +1)
size	{ width, height, top, left }	Canvas dimensions (px)
viewport	{ width, height, factor, distance, aspect }	Camera-relative metrics
invalidate	() => void	Request render in demand mode
advance	(timestamp: number) => void	Advance one tick in never mode
performance	{ current, min, max, regress() }	Adaptive performance
set	(state) => void	Mutate state directly
get	() => RootState	Read state non-reactively

Priority system: Callbacks execute in ascending priority order. When ANY callback has priority > 0, R3F disables automatic renderer.render(). The highest-priority subscriber MUST call state.gl.render(state.scene, state.camera) manually. Negative priorities do NOT disable auto-rendering.

useThree

const state = useThree()                              // full state (re-renders often)
const camera = useThree((state) => state.camera)      // selector (re-renders only on change)

Returns the RootState (same object as useFrame's state). ALWAYS use a selector when only one property is needed.

useLoader

const result = useLoader(LoaderClass, url, extensions?, onProgress?)
const results = useLoader(LoaderClass, [url1, url2], extensions?)

Suspense-based asset loading. ALWAYS wrap in <Suspense fallback={...}>.

• Assets are cached by URL -- loading the same URL twice returns the cached result.
• useLoader.preload(LoaderClass, url) preloads before component mount.
• GLTF results include { nodes, materials, scene, animations }.

useGraph

const { nodes, materials } = useGraph(object3D)

Traverses an Object3D hierarchy and returns memoized { nodes, materials } collections keyed by name.

---

Primitives and extend()

Primitives

Insert pre-existing Three.js objects into the declarative tree:

<primitive object={existingMesh} position={[10, 0, 0]} />

• NEVER add the same object instance multiple times -- Three.js objects can have only one parent.
• Primitives do NOT auto-dispose; the caller MUST manage lifecycle.

extend()

Register custom Three.js classes as JSX elements:

import { extend } from '@react-three/fiber'
import { OrbitControls } from 'three/examples/jsm/controls/OrbitControls'

extend({ OrbitControls })
// Now usable as <orbitControls args={[camera, domElement]} />

The JSX element name is the camelCase version of the registered key.

---

Event System

R3F implements pointer events via raycasting. Events bubble through the scene graph.

Supported Events

Event	Trigger
onClick	Pointer click on mesh
onContextMenu	Right-click / context menu
onDoubleClick	Double click
onPointerUp	Pointer released
onPointerDown	Pointer pressed
onPointerOver	Pointer enters mesh (fires continuously)
onPointerOut	Pointer leaves mesh
onPointerEnter	Pointer enters mesh (fires once)
onPointerLeave	Pointer leaves mesh (fires once)
onPointerMove	Pointer moves over mesh
onPointerMissed	Click hits no mesh (Canvas-level)
onWheel	Scroll wheel
onUpdate	Object receives new props

Event Object Properties

Property	Type	Description
object	THREE.Object3D	The mesh actually hit
eventObject	THREE.Object3D	Object with the event handler
point	THREE.Vector3	Intersection in world space
distance	number	Camera-to-intersection distance
uv	THREE.Vector2	UV coordinates at intersection
face	THREE.Face	Intersected face
ray	THREE.Ray	Ray used for intersection
camera	THREE.Camera	Active camera
intersections	Intersection[]	All intersected objects
delta	number	Pixel distance down-to-up
sourceEvent	Event	Original DOM event
stopPropagation()	function	Prevent bubbling to occluded objects

---

Performance Patterns

Disposal

• R3F ALWAYS calls dispose() on Three.js objects when components unmount, freeing GPU resources.
• Set dispose={null} on an element to PREVENT auto-disposal -- use when objects are shared across components.

Static Scenes

Use frameloop="demand" with invalidate() for scenes that do not animate continuously (dashboards, configurators). This saves GPU cycles.

Portals

import { createPortal } from '@react-three/fiber'

createPortal(children, targetScene)

Renders children into a different scene/layer without affecting the main scene graph.

useMemo for Imperative Objects

ALWAYS wrap imperatively created geometries and materials in useMemo:

const geometry = useMemo(() => new THREE.TorusKnotGeometry(1, 0.3, 128, 32), [])

Without useMemo, a new object is created on every render.

---

Reference Links

• references/methods.md -- Hook signatures and Canvas API
• references/examples.md -- Working R3F code examples
• references/anti-patterns.md -- What NOT to do with R3F

Official Sources

• https://r3f.docs.pmnd.rs/
• https://r3f.docs.pmnd.rs/api/canvas
• https://r3f.docs.pmnd.rs/api/hooks
• https://r3f.docs.pmnd.rs/api/events