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Three.js and TypeScript
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Design Patterns in TypeScript
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Trimeshes, ConvexPolyhedrons and Compound Shapes

Video Lecture

Trimeshes, ConvexPolyhedrons and Compound Shapes Trimeshes, ConvexPolyhedrons and Compound Shapes Trimeshes, ConvexPolyhedrons and Compound Shapes

Description

In this video I will demonstrate the performance of using several different types of Cannon shapes such as Trimeshes, ConvexPolyhedrons and Compound shapes.

A geometry in Three.js may contain many vertices and faces, so you won't always get the best performance if you use the same geometric shape in the physics engine. You may need to be more creative and optimise for a shape that delivers the best compromise. This custom shape can also sometimes be known as a collision boundary or mesh.

When positioning the parts of a compound shape, you can use a 3D graphics tool to help estimate the positioning. It is is important to know that if you use Blender, be aware that Blender by default, uses a different coordinate system. In Blender, Z is UP, and the Y axis is used for Near/Far and it is also negative compared to Threejs. So you will need to swap around the coordinates for Y and Z and negate the new Z.

To position an object from the perspective of a default Threejs camera looking down the Z axis, with UP axis [0,1,0], see table for conversion.

Axis Threejs Blender
Up/Down Y / -Y Z / -Z
Left/Right -X / X -X / X
Near/Far Z / -Z -Y / Y

E.g., If the 3D coordinate in Blender is [1,2,3], then in Threejs the equivalent is [1,3,-2]

Start Scripts

./src/client/client.ts

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import * as THREE from 'three'
import { OrbitControls } from 'three/examples/jsm/controls/OrbitControls'
import Stats from 'three/examples/jsm/libs/stats.module'
import { GUI } from 'three/examples/jsm/libs/dat.gui.module'
import { OBJLoader } from 'three/examples/jsm/loaders/OBJLoader'
import * as CANNON from 'cannon-es'
import CannonUtils from './utils/cannonUtils'
import CannonDebugRenderer from './utils/cannonDebugRenderer'
import { ConvexGeometry } from 'three/examples/jsm/geometries/ConvexGeometry'

const scene = new THREE.Scene()
scene.add(new THREE.AxesHelper(5))

var light1 = new THREE.SpotLight()
light1.position.set(2.5, 5, 5)
light1.angle = Math.PI / 4
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, 5)
light2.angle = Math.PI / 4
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,
    0.1,
    1000
)
camera.position.set(0, 4, 4)

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

const controls = new OrbitControls(camera, renderer.domElement)
controls.screenSpacePanning = true
controls.target.y = 2

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

const normalMaterial = new THREE.MeshNormalMaterial()
const phongMaterial = new THREE.MeshPhongMaterial()

let monkeyMeshes: THREE.Object3D[] = []
let monkeyBodies: CANNON.Body[] = []
let monkeyLoaded = false

const objLoader = new OBJLoader()
objLoader.load(
    'models/monkey.obj',
    (object) => {
        const monkeyMesh = object.children[0] as THREE.Mesh
        monkeyMesh.material = normalMaterial

        // const positions = monkeyMesh.geometry.attributes.position.array
        // const points: THREE.Vector3[] = []
        // for (let i = 0; i < positions.length; i += 3) {
        //     points.push(new THREE.Vector3(positions[i], positions[i + 1], positions[i + 2]))
        // }
        // const convexHull = new ConvexGeometry(points)

        for (let i = 0; i < 10; i++) {
            const monkeyMeshClone = monkeyMesh.clone()
            monkeyMeshClone.position.x = Math.floor(Math.random() * 10) - 5
            monkeyMeshClone.position.z = Math.floor(Math.random() * 10) - 5
            monkeyMeshClone.position.y = 5 + i
            scene.add(monkeyMeshClone)
            monkeyMeshes.push(monkeyMeshClone)

            const monkeyShape = CannonUtils.CreateTrimesh(
                (monkeyMesh as THREE.Mesh).geometry
            )
            // const monkeyShape = CannonUtils.CreateConvexPolyhedron(new THREE.IcosahedronGeometry(1))
            // const monkeyShape = CannonUtils.CreateConvexPolyhedron((monkeyMesh as THREE.Mesh).geometry)
            // const monkeyShape = CannonUtils.CreateConvexPolyhedron(convexHull)

            const monkeyBody = new CANNON.Body({ mass: 1 })
            monkeyBody.addShape(monkeyShape)
            // monkeyBody.addShape(new CANNON.Sphere(1))// head,
            // monkeyBody.addShape(new CANNON.Sphere(.8), new CANNON.Vec3(0, .2, 0))// head,
            // monkeyBody.addShape(new CANNON.Sphere(.05), new CANNON.Vec3(0, -.97, 0.46))// chin,
            // monkeyBody.addShape(new CANNON.Sphere(.05), new CANNON.Vec3(-1.36, .29, -0.5)) //left ear
            // monkeyBody.addShape(new CANNON.Sphere(.05), new CANNON.Vec3(1.36, .29, -0.5)) //right ear
            monkeyBody.position.x = monkeyMeshClone.position.x
            monkeyBody.position.y = monkeyMeshClone.position.y
            monkeyBody.position.z = monkeyMeshClone.position.z
            world.addBody(monkeyBody)
            monkeyBodies.push(monkeyBody)
        }

        monkeyLoaded = true
    },
    (xhr) => {
        console.log((xhr.loaded / xhr.total) * 100 + '% loaded')
    },
    (error) => {
        console.log('An error happened')
    }
)

const planeGeometry = new THREE.PlaneGeometry(25, 25)
const planeMesh = new THREE.Mesh(planeGeometry, phongMaterial)
planeMesh.rotateX(-Math.PI / 2)
planeMesh.receiveShadow = true
scene.add(planeMesh)
const planeShape = new CANNON.Plane()
const planeBody = new CANNON.Body({ mass: 0 })
planeBody.addShape(planeShape)
planeBody.quaternion.setFromAxisAngle(new CANNON.Vec3(1, 0, 0), -Math.PI / 2)
world.addBody(planeBody)

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

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

const gui = new GUI()
const physicsFolder = gui.addFolder('Physics')
physicsFolder.add(world.gravity, 'x', -10.0, 10.0, 0.1)
physicsFolder.add(world.gravity, 'y', -10.0, 10.0, 0.1)
physicsFolder.add(world.gravity, 'z', -10.0, 10.0, 0.1)
physicsFolder.open()

const clock = new THREE.Clock()
let delta

const cannonDebugRenderer = new CannonDebugRenderer(scene, world)

function animate() {
    requestAnimationFrame(animate)

    controls.update()

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

    cannonDebugRenderer.update()

    // Copy coordinates from Cannon to Three.js
    if (monkeyLoaded) {
        monkeyMeshes.forEach((m, i) => {
            m.position.set(
                monkeyBodies[i].position.x,
                monkeyBodies[i].position.y,
                monkeyBodies[i].position.z
            )
            m.quaternion.set(
                monkeyBodies[i].quaternion.x,
                monkeyBodies[i].quaternion.y,
                monkeyBodies[i].quaternion.z,
                monkeyBodies[i].quaternion.w
            )
        })
    }

    render()

    stats.update()
}

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

Final Script

./src/client/client.ts

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import * as THREE from 'three'
import { OrbitControls } from 'three/examples/jsm/controls/OrbitControls'
import Stats from 'three/examples/jsm/libs/stats.module'
import { GUI } from 'three/examples/jsm/libs/dat.gui.module'
import { OBJLoader } from 'three/examples/jsm/loaders/OBJLoader'
import * as CANNON from 'cannon-es'
import CannonUtils from './utils/cannonUtils'
import CannonDebugRenderer from './utils/cannonDebugRenderer'
import { ConvexGeometry } from 'three/examples/jsm/geometries/ConvexGeometry'

const scene = new THREE.Scene()
scene.add(new THREE.AxesHelper(5))

var light1 = new THREE.SpotLight()
light1.position.set(2.5, 5, 5)
light1.angle = Math.PI / 4
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, 5)
light2.angle = Math.PI / 4
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,
    0.1,
    1000
)
camera.position.set(0, 4, 4)

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

const controls = new OrbitControls(camera, renderer.domElement)
controls.screenSpacePanning = true
controls.target.y = 2

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

const normalMaterial = new THREE.MeshNormalMaterial()
const phongMaterial = new THREE.MeshPhongMaterial()

let monkeyMeshes: THREE.Object3D[] = []
let monkeyBodies: CANNON.Body[] = []
let monkeyLoaded = false

const objLoader = new OBJLoader()
objLoader.load(
    'models/monkey.obj',
    (object) => {
        const monkeyMesh = object.children[0] as THREE.Mesh
        monkeyMesh.material = normalMaterial

        // const positions = monkeyMesh.geometry.attributes.position.array
        // const points: THREE.Vector3[] = []
        // for (let i = 0; i < positions.length; i += 3) {
        //     points.push(new THREE.Vector3(positions[i], positions[i + 1], positions[i + 2]))
        // }
        // const convexHull = new ConvexGeometry(points)

        for (let i = 0; i < 200; i++) {
            const monkeyMeshClone = monkeyMesh.clone()
            monkeyMeshClone.position.x = Math.floor(Math.random() * 10) - 5
            monkeyMeshClone.position.z = Math.floor(Math.random() * 10) - 5
            monkeyMeshClone.position.y = 5 + i
            scene.add(monkeyMeshClone)
            monkeyMeshes.push(monkeyMeshClone)

            // const monkeyShape = CannonUtils.CreateTrimesh((monkeyMesh as THREE.Mesh).geometry)
            // const monkeyShape = CannonUtils.CreateConvexPolyhedron(new THREE.IcosahedronGeometry(1))
            // const monkeyShape = CannonUtils.CreateConvexPolyhedron((monkeyMesh as THREE.Mesh).geometry)
            // const monkeyShape = CannonUtils.CreateConvexPolyhedron(convexHull)

            const monkeyBody = new CANNON.Body({ mass: 1 })
            // monkeyBody.addShape(monkeyShape)
            // monkeyBody.addShape(new CANNON.Sphere(1))// head,
            monkeyBody.addShape(
                new CANNON.Sphere(0.8),
                new CANNON.Vec3(0, 0.2, 0)
            ) // head,
            monkeyBody.addShape(
                new CANNON.Sphere(0.05),
                new CANNON.Vec3(0, -0.97, 0.46)
            ) // chin,
            monkeyBody.addShape(
                new CANNON.Sphere(0.05),
                new CANNON.Vec3(-1.36, 0.29, -0.5)
            ) //left ear
            monkeyBody.addShape(
                new CANNON.Sphere(0.05),
                new CANNON.Vec3(1.36, 0.29, -0.5)
            ) //right ear
            monkeyBody.position.x = monkeyMeshClone.position.x
            monkeyBody.position.y = monkeyMeshClone.position.y
            monkeyBody.position.z = monkeyMeshClone.position.z
            world.addBody(monkeyBody)
            monkeyBodies.push(monkeyBody)
        }

        monkeyLoaded = true
    },
    (xhr) => {
        console.log((xhr.loaded / xhr.total) * 100 + '% loaded')
    },
    (error) => {
        console.log('An error happened')
    }
)

const planeGeometry = new THREE.PlaneGeometry(25, 25)
const planeMesh = new THREE.Mesh(planeGeometry, phongMaterial)
planeMesh.rotateX(-Math.PI / 2)
planeMesh.receiveShadow = true
scene.add(planeMesh)
const planeShape = new CANNON.Plane()
const planeBody = new CANNON.Body({ mass: 0 })
planeBody.addShape(planeShape)
planeBody.quaternion.setFromAxisAngle(new CANNON.Vec3(1, 0, 0), -Math.PI / 2)
world.addBody(planeBody)

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

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

const gui = new GUI()
const physicsFolder = gui.addFolder('Physics')
physicsFolder.add(world.gravity, 'x', -10.0, 10.0, 0.1)
physicsFolder.add(world.gravity, 'y', -10.0, 10.0, 0.1)
physicsFolder.add(world.gravity, 'z', -10.0, 10.0, 0.1)
physicsFolder.open()

const clock = new THREE.Clock()
let delta

const cannonDebugRenderer = new CannonDebugRenderer(scene, world)

function animate() {
    requestAnimationFrame(animate)

    controls.update()

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

    //cannonDebugRenderer.update()

    // Copy coordinates from Cannon to Three.js
    if (monkeyLoaded) {
        monkeyMeshes.forEach((m, i) => {
            m.position.set(
                monkeyBodies[i].position.x,
                monkeyBodies[i].position.y,
                monkeyBodies[i].position.z
            )
            m.quaternion.set(
                monkeyBodies[i].quaternion.x,
                monkeyBodies[i].quaternion.y,
                monkeyBodies[i].quaternion.z,
                monkeyBodies[i].quaternion.w
            )
        })
    }

    render()

    stats.update()
}

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