npm package: @react-three/p2
Description: 2D physics based hooks for react-three-fiber
Author: Joerg Jaeckel
Latest version: 0.0.6

    yarn add @react-three/p2

React hooks for [p2-es](https://github.com/pmndrs/p2-es). Use this in combination with [react-three-fiber](https://github.com/pmndrs/react-three-fiber).

- [x] Doesn't block the main thread, runs in a web worker
- [ ] Supports instancing out of the box

## TODOs

##### Shapes

- [x] useBox
- [x] useCapsule
- [x] useCircle
- [x] useConvex
- [x] useHeightfield
- [x] useLine
- [x] useParticle
- [x] usePlane

##### Raycast

- [x] useRaycastAny
- [x] useRaycastAll
- [x] useRaycastClosest

#### Springs

- [ ] LinearSpring
- [ ] RotationalSpring
- [ ] Spring?

#### Constraints

- [x] DistanceConstraint
- [x] GearConstraint
- [x] LockConstraint
- [x] PrismaticConstraint
- [x] RevoluteConstraint

#### Other

- [x] useTopDownVehicle
- [x] useKinematicCharacterController
- [x] usePlatformController

## Demos

Check out all of our examples at https://p2.pmnd.rs (coming soon)

Meanwhile look at the examples living in [./examples](./examples)

## How it works

1. Get all the imports that you need.

```jsx
import { Physics, useBox, ... } from '@react-three/p2'
```

2. Create a physics world. normalIndex defines the rotation of the physics world in space. Use `1` for top-down and `2` for side-scroller like apps.

```jsx
<Physics normalIndex={2}>{/* Physics related objects in here please */}</Physics>
```

3. Pick a shape that suits your objects contact surface, it could be a box, plane, circle, etc. Give it a mass, too.

```jsx
const [ref, api] = useBox(() => ({ mass: 1 }))
```

4. Take your object, it could be a mesh, line, gltf, anything, and tie it to the reference you have just received. Et voilà, it will now be affected by gravity and other objects inside the physics world.

```jsx
<mesh ref={ref} geometry={...} material={...} />
```

5. You can interact with it by using [the api](#returned-api), which lets you apply positions, rotations, velocities, forces and impulses.

```jsx
useFrame(({ clock }) => api.position.set(Math.sin(clock.getElapsedTime()) * 5, 0))
```

6. You can use the body api to subscribe to properties to get updates on each frame.

```jsx
const velocity = useRef([0, 0])
useEffect(() => {
  const unsubscribe = api.velocity.subscribe((v) => (velocity.current = v))
  return unsubscribe
}, [])
```

## Simple example

Let's make a ball falling onto a box.

```jsx
import { Canvas } from '@react-three/fiber'
import { Physics, useBox, useCircle } from '@react-three/p2'

function Box() {
  const [ref] = useBox(() => ({ mass: 0, position: [0, -2] }))
  return (
    <mesh ref={ref}>
      <boxGeometry />
    </mesh>
  )
}

function Ball() {
  const [ref] = useCircle(() => ({ mass: 1, position: [0, 2] }))
  return (
    <mesh ref={ref}>
      <sphereGeometry />
    </mesh>
  )
}

ReactDOM.render(
  <Canvas>
    <Physics normalIndex={2}>
      <Box />
      <Ball />
    </Physics>
  </Canvas>,
  document.getElementById('root'),
)
```

## Debug

You can debug your scene using the `p2-es-debugger`. This will show you how p2 "sees" your scene. Don't forget to tell both the same normalIndex.

```jsx
import { Physics, Debug } from '@react-three/cannon'

ReactDOM.render(
  <Canvas>
    <Physics normalIndex={2}>
      <Debug color="black" scale={1.1} linewidth={0.01} normalIndex={2}>
        {/* children */}
      </Debug>
    </Physics>
  </Canvas>,
  document.getElementById('root'),
)
```

## Api

### Exports

```typescript
function Physics({
  allowSleep = false,
  axisIndex = 0,
  normalIndex = 0,
  broadphase = 'Naive',
  children,
  defaultContactMaterial = { contactEquationStiffness: 1e6 },
  gravity = [0, -9.81, 0],
  isPaused = false,
  iterations = 5,
  maxSubSteps = 10,
  quatNormalizeFast = false,
  quatNormalizeSkip = 0,
  shouldInvalidate = true,
  // Maximum amount of physics objects inside your scene
  // Lower this value to save memory, increase if 1000 isn't enough
  size = 1000,
  solver = 'GS',
  stepSize = 1 / 60,
  tolerance = 0.001,
}: React.PropsWithChildren<ProviderProps>): JSX.Element

function Debug({ color = 'black', scale = 1 }: DebugProps): JSX.Element

function usePlane(
  fn: GetByIndex<PlaneProps>,
  fwdRef?: React.Ref<THREE.Object3D>,
  deps?: React.DependencyList,
): Api

function useBox(
  fn: GetByIndex<BoxProps>,
  fwdRef?: React.Ref<THREE.Object3D>,
  deps?: React.DependencyList,
): Api

function useCircle(
  fn: GetByIndex<CylinderProps>,
  fwdRef?: React.Ref<THREE.Object3D>,
  deps?: React.DependencyList,
): Api

function useTopDownVehicle(
  fn: () => RaycastVehicleProps,
  fwdRef?: React.Ref<THREE.Object3D>,
  deps: React.DependencyList[] = [],
): [React.RefObject<THREE.Object3D>, RaycastVehiclePublicApi]

function useRaycastClosest(
  options: RayOptions,
  callback: (e: RayhitEvent) => void,
  deps: React.DependencyList = [],
): void

function useRaycastAny(
  options: RayOptions,
  callback: (e: RayhitEvent) => void,
  deps: React.DependencyList = [],
): void

function useRaycastAll(
  options: RayOptions,
  callback: (e: RayhitEvent) => void,
  deps: React.DependencyList = [],
): void
```

### Returned api

```typescript
type WorkerApi = {
  [K in AtomicName]: AtomicApi<K>
} & {
  [K in VectorName]: VectorApi
} & {
  applyForce: (force: Triplet, worldPoint: Triplet) => void
  applyImpulse: (impulse: Triplet, worldPoint: Triplet) => void
  applyLocalForce: (force: Triplet, localPoint: Triplet) => void
  applyLocalImpulse: (impulse: Triplet, localPoint: Triplet) => void
  applyTorque: (torque: Triplet) => void
  quaternion: QuaternionApi
  rotation: VectorApi
  sleep: () => void
  wakeUp: () => void
}

interface PublicApi extends WorkerApi {
  at: (index: number) => WorkerApi
}

type Api = [React.RefObject<THREE.Object3D>, PublicApi]

type AtomicName =
  | 'allowSleep'
  | 'angularDamping'
  | 'collisionGroup'
  | 'collisionMask'
  | 'collisionResponse'
  | 'fixedRotation'
  | 'isTrigger'
  | 'linearDamping'
  | 'mass'
  | 'material'
  | 'sleepSpeedLimit'
  | 'sleepTimeLimit'
  | 'userData'

type AtomicApi<K extends AtomicName> = {
  set: (value: AtomicProps[K]) => void
  subscribe: (callback: (value: AtomicProps[K]) => void) => () => void
}

type QuaternionApi = {
  set: (x: number, y: number, z: number, w: number) => void
  copy: ({ w, x, y, z }: Quaternion) => void
  subscribe: (callback: (value: Quad) => void) => () => void
}

type VectorName = 'angularFactor' | 'angularVelocity' | 'linearFactor' | 'position' | 'velocity'

type VectorApi = {
  set: (x: number, y: number, z: number) => void
  copy: ({ x, y, z }: Vector3 | Euler) => void
  subscribe: (callback: (value: Triplet) => void) => () => void
}

type ConstraintApi = [
  React.RefObject<THREE.Object3D>,
  React.RefObject<THREE.Object3D>,
  {
    enable: () => void
    disable: () => void
  },
]

type HingeConstraintApi = [
  React.RefObject<THREE.Object3D>,
  React.RefObject<THREE.Object3D>,
  {
    enable: () => void
    disable: () => void
    enableMotor: () => void
    disableMotor: () => void
    setMotorSpeed: (value: number) => void
    setMotorMaxForce: (value: number) => void
  },
]

type SpringApi = [
  React.RefObject<THREE.Object3D>,
  React.RefObject<THREE.Object3D>,
  {
    setStiffness: (value: number) => void
    setRestLength: (value: number) => void
    setDamping: (value: number) => void
  },
]

interface RaycastVehiclePublicApi {
  applyEngineForce: (value: number, wheelIndex: number) => void
  setBrake: (brake: number, wheelIndex: number) => void
  setSteeringValue: (value: number, wheelIndex: number) => void
  sliding: {
    subscribe: (callback: (sliding: boolean) => void) => void
  }
}
```

### Props

```typescript
type InitProps = {
  allowSleep?: boolean
  axisIndex?: number
  broadphase?: Broadphase
  defaultContactMaterial?: {
    friction?: number
    restitution?: number
    contactEquationStiffness?: number
    contactEquationRelaxation?: number
    frictionEquationStiffness?: number
    frictionEquationRelaxation?: number
  }
  gravity?: Duplet
  iterations?: number
  normalIndex?: number
  quatNormalizeFast?: boolean
  quatNormalizeSkip?: number
  solver?: Solver
  tolerance?: number
}

export type ProviderProps = InitProps & {
  isPaused?: boolean
  maxSubSteps?: number
  shouldInvalidate?: boolean
  size?: number
  stepSize?: number
}

type AtomicProps = {
  allowSleep: boolean
  angularDamping: number
  collisionFilterGroup: number
  collisionFilterMask: number
  collisionResponse: number
  fixedRotation: boolean
  isTrigger: boolean
  linearDamping: number
  mass: number
  material: MaterialOptions
  sleepSpeedLimit: number
  sleepTimeLimit: number
  userData: {}
}

type Broadphase = 'Naive' | 'SAP'
type Triplet = [x: number, y: number, z: number]
type Quad = [x: number, y: number, z: number, w: number]

type VectorProps = Record<VectorName, Triplet>

type BodyProps<T extends any[] = unknown[]> = Partial<AtomicProps> &
  Partial<VectorProps> & {
    args?: T
    onCollide?: (e: CollideEvent) => void
    onCollideBegin?: (e: CollideBeginEvent) => void
    onCollideEnd?: (e: CollideEndEvent) => void
    quaternion?: Quad
    rotation?: Triplet
    type?: 'Dynamic' | 'Static' | 'Kinematic'
  }

type Event = RayhitEvent | CollideEvent | CollideBeginEvent | CollideEndEvent
type CollideEvent = {
  op: string
  type: 'collide'
  body: THREE.Object3D
  target: THREE.Object3D
  contact: {
    // the world position of the point of contact
    contactPoint: number[]
    // the normal of the collision on the surface of
    // the colliding body
    contactNormal: number[]
    // velocity of impact along the contact normal
    impactVelocity: number
    // a unique ID for each contact event
    id: string
    // these are lower-level properties from cannon:
    // bi: one of the bodies involved in contact
    bi: THREE.Object3D
    // bj: the other body involved in contact
    bj: THREE.Object3D
    // ni: normal of contact relative to bi
    ni: number[]
    // ri: the point of contact relative to bi
    ri: number[]
    // rj: the point of contact relative to bj
    rj: number[]
  }
  collisionFilters: {
    bodyFilterGroup: number
    bodyFilterMask: number
    targetFilterGroup: number
    targetFilterMask: number
  }
}
type CollideBeginEvent = {
  op: 'event'
  type: 'collideBegin'
  target: Object3D
  body: Object3D
}
type CollideEndEvent = {
  op: 'event'
  type: 'collideEnd'
  target: Object3D
  body: Object3D
}
type RayhitEvent = {
  op: string
  type: 'rayhit'
  body: THREE.Object3D
  target: THREE.Object3D
}

type CylinderArgs = [radiusTop?: number, radiusBottom?: number, height?: number, numSegments?: number]
type SphereArgs = [radius: number]
type TrimeshArgs = [vertices: ArrayLike<number>, indices: ArrayLike<number>]
type HeightfieldArgs = [
  data: number[][],
  options: { elementSize?: number; maxValue?: number; minValue?: number },
]
type ConvexPolyhedronArgs<V extends VectorTypes = VectorTypes> = [
  vertices?: V[],
  faces?: number[][],
  normals?: V[],
  axes?: V[],
  boundingSphereRadius?: number,
]

interface PlaneProps extends BodyProps {}
interface BoxProps extends BodyProps<Triplet> {} // extents: [x, y, z]
interface CylinderProps extends BodyProps<CylinderArgs> {}
interface ParticleProps extends BodyProps {}
interface SphereProps extends BodyProps<SphereArgs> {}
interface TrimeshProps extends BodyPropsArgsRequired<TrimeshArgs> {}
interface HeightfieldProps extends BodyPropsArgsRequired<HeightfieldArgs> {}
interface ConvexPolyhedronProps extends BodyProps<ConvexPolyhedronArgs> {}
interface CompoundBodyProps extends BodyProps {
  shapes: BodyProps & { type: ShapeType }[]
}

interface ConstraintOptns {
  maxForce?: number
  collideConnected?: boolean
  wakeUpBodies?: boolean
}

interface PointToPointConstraintOpts extends ConstraintOptns {
  pivotA: Triplet
  pivotB: Triplet
}

interface ConeTwistConstraintOpts extends ConstraintOptns {
  pivotA?: Triplet
  axisA?: Triplet
  pivotB?: Triplet
  axisB?: Triplet
  angle?: number
  twistAngle?: number
}
interface DistanceConstraintOpts extends ConstraintOptns {
  distance?: number
}

interface HingeConstraintOpts extends ConstraintOptns {
  pivotA?: Triplet
  axisA?: Triplet
  pivotB?: Triplet
  axisB?: Triplet
}

interface LockConstraintOpts extends ConstraintOptns {}

interface SpringOptns {
  restLength?: number
  stiffness?: number
  damping?: number
  worldAnchorA?: Triplet
  worldAnchorB?: Triplet
  localAnchorA?: Triplet
  localAnchorB?: Triplet
}

interface WheelInfoOptions {
  radius?: number
  directionLocal?: Triplet
  suspensionStiffness?: number
  suspensionRestLength?: number
  maxSuspensionForce?: number
  maxSuspensionTravel?: number
  dampingRelaxation?: number
  dampingCompression?: number
  frictionSlip?: number
  rollInfluence?: number
  axleLocal?: Triplet
  chassisConnectionPointLocal?: Triplet
  isFrontWheel?: boolean
  useCustomSlidingRotationalSpeed?: boolean
  customSlidingRotationalSpeed?: number
}

interface RaycastVehicleProps {
  chassisBody: React.Ref<THREE.Object3D>
  wheels: React.Ref<THREE.Object3D>[]
  wheelInfos: WheelInfoOptions[]
  indexForwardAxis?: number
  indexRightAxis?: number
  indexUpAxis?: number
}
```

### FAQ

#### Broadphases

- NaiveBroadphase is as simple as it gets. It considers every body to be a potential collider with every other body. This results in the maximum number of narrowphase checks.
- SAPBroadphase sorts bodies along an axis and then moves down that list finding pairs by looking at body size and position of the next bodies. Control what axis to sort along by setting the axisIndex property.

#### Types

- A dynamic body is fully simulated. Can be moved manually by the user, but normally they move according to forces. A dynamic body can collide with all body types. A dynamic body always has finite, non-zero mass.
- A static body does not move during simulation and behaves as if it has infinite mass. Static bodies can be moved manually by setting the position of the body. The velocity of a static body is always zero. Static bodies do not collide with other static or kinematic bodies.
- A kinematic body moves under simulation according to its velocity. They do not respond to forces. They can be moved manually, but normally a kinematic body is moved by setting its velocity. A kinematic body behaves as if it has infinite mass. Kinematic bodies do not collide with other static or kinematic bodies.