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Follow Cam

Description

In this custom implementation of a follow cam, I have a camera pivot, which I attach to an object that I want to follow. The pivot can be rotated by moving the mouse left, right, up and down.

Another THREE.Object3D is attached to the pivot, but at several units behind or in front. The distance can be changed using the scroll wheel.

The pivot follows the main character of my scene. The scene camera lerps and slerps to the Object3D attached to the pivot.

./src/client/client.ts

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import * as THREE from 'three'
import { PointerLockControls } from 'three/examples/jsm/controls/PointerLockControls'
import { GLTFLoader } from 'three/examples/jsm/loaders/GLTFLoader'
import Stats from 'three/examples/jsm/libs/stats.module'
import * as CANNON from 'cannon-es'
import CannonDebugRenderer from './utils/cannonDebugRenderer'

const scene = new THREE.Scene()

var light1 = new THREE.SpotLight()
light1.position.set(2.5, 5, 2.5)
light1.angle = Math.PI / 8
light1.penumbra = 0.5
light1.castShadow = true
light1.shadow.mapSize.width = 1024
light1.shadow.mapSize.height = 1024
light1.shadow.camera.near = 0.5
light1.shadow.camera.far = 20
scene.add(light1)

var light2 = new THREE.SpotLight()
light2.position.set(-2.5, 5, 2.5)
light2.angle = Math.PI / 8
light2.penumbra = 0.5
light2.castShadow = true
light2.shadow.mapSize.width = 1024
light2.shadow.mapSize.height = 1024
light2.shadow.camera.near = 0.5
light2.shadow.camera.far = 20
scene.add(light2)

const camera = new THREE.PerspectiveCamera(
    75,
    window.innerWidth / window.innerHeight,
    0.01,
    100
)
camera.position.set(0, 1.4, 2.0)

const followCamPivot = new THREE.Object3D()
followCamPivot.rotation.order = 'YXZ'
const followCam = new THREE.Object3D()
followCam.position.z = 2
followCamPivot.add(followCam)

const renderer = new THREE.WebGLRenderer()
renderer.setSize(window.innerWidth, window.innerHeight)
renderer.outputEncoding = THREE.sRGBEncoding
renderer.shadowMap.enabled = true
document.body.appendChild(renderer.domElement)

const world = new CANNON.World()
world.gravity.set(0, -9.82, 0)

const groundMaterial = new CANNON.Material('groundMaterial')
const slipperyMaterial = new CANNON.Material('slipperyMaterial')
const slippery_ground_cm = new CANNON.ContactMaterial(
    groundMaterial,
    slipperyMaterial,
    {
        friction: 0,
        restitution: 0.3,
        contactEquationStiffness: 1e8,
        contactEquationRelaxation: 3,
    }
)
world.addContactMaterial(slippery_ground_cm)

// Character Collider
const characterCollider = new THREE.Object3D()
characterCollider.add(followCamPivot)
characterCollider.position.y = 3
scene.add(characterCollider)
const colliderShape = new CANNON.Sphere(0.5)
const colliderBody = new CANNON.Body({ mass: 1, material: slipperyMaterial })
colliderBody.addShape(colliderShape, new CANNON.Vec3(0, 0.5, 0))
colliderBody.addShape(colliderShape, new CANNON.Vec3(0, -0.5, 0))
colliderBody.position.set(
    characterCollider.position.x,
    characterCollider.position.y,
    characterCollider.position.z
)
colliderBody.linearDamping = 0.95
colliderBody.angularFactor.set(0, 1, 0) // prevents rotation X,Z axis
world.addBody(colliderBody)

let mixer: THREE.AnimationMixer
let modelReady = false
let modelMesh: THREE.Object3D
const animationActions: THREE.AnimationAction[] = []
let activeAction: THREE.AnimationAction
let lastAction: THREE.AnimationAction

const gltfLoader = new GLTFLoader()
gltfLoader.load(
    'models/eve.glb',
    (gltf) => {
        gltf.scene.traverse(function (child) {
            if ((child as THREE.Mesh).isMesh) {
                let m = child
                m.receiveShadow = true
                m.castShadow = true
                m.frustumCulled = false
                ;(m as THREE.Mesh).geometry.computeVertexNormals()
                if ((child as THREE.Mesh).material) {
                    const mat = (child as THREE.Mesh).material
                    ;(mat as THREE.Material).transparent = false
                    ;(mat as THREE.Material).side = THREE.FrontSide
                }
            }
        })
        mixer = new THREE.AnimationMixer(gltf.scene)
        let animationAction = mixer.clipAction(gltf.animations[0])
        animationActions.push(animationAction)
        activeAction = animationActions[0]
        scene.add(gltf.scene)
        modelMesh = gltf.scene
        light1.target = modelMesh
        light2.target = modelMesh

        //add an animation from another file
        gltfLoader.load(
            'models/eve@walking.glb',
            (gltf) => {
                console.log('loaded Eve walking')
                let animationAction = mixer.clipAction(gltf.animations[0])
                animationActions.push(animationAction)

                gltfLoader.load(
                    'models/eve@jump.glb',
                    (gltf) => {
                        console.log('loaded Eve jump')
                        gltf.animations[0].tracks.shift() //delete the specific track that moves the object up/down while jumping
                        let animationAction = mixer.clipAction(
                            gltf.animations[0]
                        )
                        animationActions.push(animationAction)
                        //progressBar.style.display = 'none'
                        modelReady = true

                        setAction(animationActions[1], true)
                    },
                    (xhr) => {
                        if (xhr.lengthComputable) {
                            //const percentComplete = (xhr.loaded / xhr.total) * 100
                            //progressBar.value = percentComplete
                            //progressBar.style.display = 'block'
                        }
                    },
                    (error) => {
                        console.log(error)
                    }
                )
            },
            (xhr) => {
                if (xhr.lengthComputable) {
                    //const percentComplete = (xhr.loaded / xhr.total) * 100
                    //progressBar.value = percentComplete
                    //progressBar.style.display = 'block'
                }
            },
            (error) => {
                console.log(error)
            }
        )
    },
    (xhr) => {
        if (xhr.lengthComputable) {
            //const percentComplete = (xhr.loaded / xhr.total) * 100
            //progressBar.value = percentComplete
            //progressBar.style.display = 'block'
        }
    },
    (error) => {
        console.log(error)
    }
)

const setAction = (toAction: THREE.AnimationAction, loop: Boolean) => {
    if (toAction != activeAction) {
        lastAction = activeAction
        activeAction = toAction
        lastAction.fadeOut(0.1)
        activeAction.reset()
        activeAction.fadeIn(0.1)
        activeAction.play()
        if (!loop) {
            activeAction.clampWhenFinished = true
            activeAction.loop = THREE.LoopOnce
        }
    }
}

let moveForward = false
let moveBackward = false
let moveLeft = false
let moveRight = false
let canJump = true
const contactNormal = new CANNON.Vec3()
const upAxis = new CANNON.Vec3(0, 1, 0)
colliderBody.addEventListener('collide', function (e: any) {
    const contact = e.contact
    if (contact.bi.id == colliderBody.id) {
        contact.ni.negate(contactNormal)
    } else {
        contactNormal.copy(contact.ni)
    }
    if (contactNormal.dot(upAxis) > 0.5) {
        if (!canJump) {
            setAction(animationActions[1], true)
        }
        canJump = true
    }
})

const planeGeometry = new THREE.PlaneGeometry(100, 100)
const texture = new THREE.TextureLoader().load('img/grid.png')
const plane = new THREE.Mesh(
    planeGeometry,
    new THREE.MeshPhongMaterial({ map: texture })
)
plane.rotateX(-Math.PI / 2)
plane.receiveShadow = true
scene.add(plane)
const planeShape = new CANNON.Plane()
const planeBody = new CANNON.Body({ mass: 0, material: groundMaterial })
planeBody.addShape(planeShape)
planeBody.quaternion.setFromAxisAngle(new CANNON.Vec3(1, 0, 0), -Math.PI / 2)
world.addBody(planeBody)

const boxes: CANNON.Body[] = []
const boxMeshes: THREE.Mesh[] = []
for (let i = 0; i < 50; i++) {
    const halfExtents = new CANNON.Vec3(
        Math.random() * 2,
        Math.random() * 2,
        Math.random() * 2
    )
    const boxShape = new CANNON.Box(halfExtents)
    const boxGeometry = new THREE.BoxGeometry(
        halfExtents.x * 2,
        halfExtents.y * 2,
        halfExtents.z * 2
    )
    const x = (Math.random() - 0.5) * 20
    const y = 2 + i * 2
    const z = (Math.random() - 0.5) * 20
    const boxBody = new CANNON.Body({ mass: 1, material: groundMaterial })
    boxBody.addShape(boxShape)
    const boxMesh = new THREE.Mesh(boxGeometry, new THREE.MeshStandardMaterial())
    world.addBody(boxBody)
    scene.add(boxMesh)
    boxBody.position.set(x, y, z)
    boxMesh.castShadow = true
    boxMesh.receiveShadow = true
    boxes.push(boxBody)
    boxMeshes.push(boxMesh)
}

const menuPanel = document.getElementById('menuPanel') as HTMLDivElement
const startButton = document.getElementById('startButton') as HTMLInputElement
startButton.addEventListener(
    'click',
    () => {
        controls.lock()
    },
    false
)

const controls = new PointerLockControls(camera, renderer.domElement)

controls.addEventListener('lock', () => {
    startButton.style.display = 'none'
    menuPanel.style.display = 'none'

    document.addEventListener('keydown', onDocumentKey, false)
    document.addEventListener('keyup', onDocumentKey, false)

    renderer.domElement.addEventListener(
        'mousemove',
        onDocumentMouseMove,
        false
    )
    renderer.domElement.addEventListener(
        'mousewheel',
        onDocumentMouseWheel,
        false
    )
})

controls.addEventListener('unlock', () => {
    menuPanel.style.display = 'block'

    document.removeEventListener('keydown', onDocumentKey, false)
    document.removeEventListener('keyup', onDocumentKey, false)

    renderer.domElement.removeEventListener(
        'mousemove',
        onDocumentMouseMove,
        false
    )
    renderer.domElement.removeEventListener(
        'mousewheel',
        onDocumentMouseWheel,
        false
    )

    setTimeout(() => {
        startButton.style.display = 'block'
    }, 1000)
})

window.addEventListener('resize', onWindowResize, false)
function onWindowResize() {
    camera.aspect = window.innerWidth / window.innerHeight
    camera.updateProjectionMatrix()
    renderer.setSize(window.innerWidth, window.innerHeight)
    render()
}

const onDocumentMouseMove = (e: MouseEvent) => {
    followCamPivot.rotation.y -= e.movementX * 0.002
    followCamPivot.rotation.x -= e.movementY * 0.002
    return false
}

const onDocumentMouseWheel = (e: THREE.Event) => {
    let newVal = followCam.position.z + e.deltaY * 0.05
    if (newVal > 0.25 && newVal < 10) {
        followCam.position.z = newVal
    }
    return false
}

const keyMap: { [id: string]: boolean } = {}
const onDocumentKey = (e: KeyboardEvent) => {
    keyMap[e.code] = e.type === 'keydown'

    if (controls.isLocked) {
        moveForward = keyMap['KeyW']
        moveBackward = keyMap['KeyS']
        moveLeft = keyMap['KeyA']
        moveRight = keyMap['KeyD']

        if (keyMap['Space']) {
            if (canJump === true) {
                colliderBody.velocity.y = 10
                setAction(animationActions[2], false)
            }
            canJump = false
        }
    }
}

const inputVelocity = new THREE.Vector3()
const velocity = new CANNON.Vec3()
const euler = new THREE.Euler()
const quat = new THREE.Quaternion()
const camTo = new THREE.Vector3()
const targetQuaternion = new THREE.Quaternion()
let distance = 0

const stats = Stats()
document.body.appendChild(stats.dom)

const clock = new THREE.Clock()
let delta = 0

//const cannonDebugRenderer = new CannonDebugRenderer(scene, world)

function animate() {
    requestAnimationFrame(animate)

    if (modelReady) {
        if (canJump) {
            //walking
            mixer.update(delta * distance * 5)
        } else {
            //were in the air
            mixer.update(delta)
        }
        const p = characterCollider.position
        p.y -= 1
        modelMesh.position.y = characterCollider.position.y
        distance = modelMesh.position.distanceTo(p)

        const rotationMatrix = new THREE.Matrix4()
        rotationMatrix.lookAt(p, modelMesh.position, modelMesh.up)
        targetQuaternion.setFromRotationMatrix(rotationMatrix)

        if (!modelMesh.quaternion.equals(targetQuaternion)) {
            modelMesh.quaternion.rotateTowards(targetQuaternion, delta * 10)
        }

        if (canJump) {
            inputVelocity.set(0, 0, 0)

            if (moveForward) {
                inputVelocity.z = -10 * delta
            }
            if (moveBackward) {
                inputVelocity.z = 10 * delta
            }

            if (moveLeft) {
                inputVelocity.x = -10 * delta
            }
            if (moveRight) {
                inputVelocity.x = 10 * delta
            }

            // apply camera rotation to inputVelocity
            euler.y = followCamPivot.rotation.y
            euler.order = 'XYZ'
            quat.setFromEuler(euler)
            inputVelocity.applyQuaternion(quat)
        }

        modelMesh.position.lerp(characterCollider.position, 0.1)
    }
    velocity.set(inputVelocity.x, inputVelocity.y, inputVelocity.z)
    colliderBody.applyImpulse(velocity)

    delta = Math.min(clock.getDelta(), 0.1)
    world.step(delta)

    //cannonDebugRenderer.update()

    characterCollider.position.set(
        colliderBody.position.x,
        colliderBody.position.y,
        colliderBody.position.z
    )
    boxes.forEach((b, i) => {
        boxMeshes[i].position.set(b.position.x, b.position.y, b.position.z)
        boxMeshes[i].quaternion.set(
            b.quaternion.x,
            b.quaternion.y,
            b.quaternion.z,
            b.quaternion.w
        )
    })

    followCam.getWorldPosition(camTo)
    camera.position.lerpVectors(camera.position, camTo, 0.1)

    render()

    stats.update()
}

function render() {
    renderer.render(scene, camera)
}

animate()