pmndrs · age2pierre · Mar 4, 2021 · Mar 5, 2021 · Mar 5, 2021
diff --git a/examples/js/Demo.js b/examples/js/Demo.js
@@ -547,6 +547,7 @@ class Demo extends CANNON.EventTarget {
     this.currentMaterial = this.solidMaterial
     const contactDotMaterial = new THREE.MeshBasicMaterial({ color: 0xffffff })
     this.particleMaterial = new THREE.MeshLambertMaterial({ color: 0xff0000 })
+    this.triggerMaterial = new THREE.MeshBasicMaterial({ color: 0x00ff00, wireframe: true })
 
     const contactPointGeometry = new THREE.SphereGeometry(0.1, 6, 6)
     this.contactMeshCache = new GeometryCache(this.scene, () => {
@@ -894,10 +895,9 @@ class Demo extends CANNON.EventTarget {
       throw new Error('The argument passed to addVisual() is not a body')
     }
 
-    // if it's a particle paint it red, otherwise just gray
-    const material = body.shapes.every((s) => s instanceof CANNON.Particle)
-      ? this.particleMaterial
-      : this.currentMaterial
+    // if it's a particle paint it red, if it's a trigger paint it as green, otherwise just gray
+    const isParticule = body.shapes.every((s) => s instanceof CANNON.Particle)
+    const material = isParticule ? this.particleMaterial : body.isTrigger ? this.triggerMaterial : this.currentMaterial
 
     // get the correspondant three.js mesh
     const mesh = bodyToMesh(body, material)

diff --git a/examples/trigger.html b/examples/trigger.html
@@ -0,0 +1,68 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8" />
+    <title>cannon.js - trigger demo</title>
+    <link rel="stylesheet" href="css/style.css" type="text/css" />
+    <meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0" />
+  </head>
+  <body>
+    <script type="module">
+      import * as CANNON from '../dist/cannon-es.js'
+      import { Demo } from './js/Demo.js'
+
+      /**
+       * Demonstrates how to make use of trigger to allow others body to pass through them, yet still emit collision events
+       */
+      const demo = new Demo()
+
+      demo.addScene('Trigger', () => {
+        const world = setupWorld(demo)
+
+        const boxShape = new CANNON.Box(new CANNON.Vec3(1, 1, 1))
+        const sphereShape = new CANNON.Sphere(1)
+
+        // Trigger body
+        const triggerBox = new CANNON.Body({ isTrigger: true })
+        triggerBox.addShape(boxShape)
+        triggerBox.position.set(-5, 0, 0)
+        world.addBody(triggerBox)
+        demo.addVisual(triggerBox)
+
+        // Sphere
+        const movingSphere = new CANNON.Body({ mass: 5 })
+        movingSphere.addShape(sphereShape)
+        movingSphere.position.set(5, 0, 0)
+        movingSphere.velocity.set(-5, 0, 0)
+        movingSphere.linearDamping = 0
+        world.addBody(movingSphere)
+        demo.addVisual(movingSphere)
+
+        // When a body collides with another body, they both dispatch the "collide" event.
+        triggerBox.addEventListener('collide', (event) => {
+          console.log('The box trigger was collided!', event)
+        })
+        movingSphere.addEventListener('collide', (event) => {
+          console.log('The sphere was collided!', event)
+        })
+
+        // When two bodies collide they also emit contact events
+        world.addEventListener('endContact', (event) => {
+          console.log('World end contact event', event)
+        })
+        world.addEventListener('beginContact', (event) => {
+          console.log('World begin contact event', event)
+        })
+      })
+
+      demo.start()
+
+      function setupWorld(demo) {
+        const world = demo.getWorld()
+        world.gravity.set(0, 0, 0) // no gravity
+
+        return world
+      }
+    </script>
+  </body>
+</html>
diff --git a/index.html b/index.html
@@ -153,6 +153,7 @@
         'spring',
         'stacks',
         'tear',
+        'trigger',
         'trimesh',
         'tween',
       ]

diff --git a/readme.md b/readme.md
@@ -15,6 +15,7 @@ These minor changes and improvements were also made:
 - Added a property `World.hasActiveBodies: boolean` which will be false when all physics bodies are sleeping. This allows for invalidating frames when physics aren't active for increased performance.
 - Deprecated properties and methods have been removed.
 - The [original cannon.js debugger](https://github.com/schteppe/cannon.js/blob/master/tools/threejs/CannonDebugRenderer.js), which shows the wireframes of each body, has been moved to its own repo [cannon-es-debugger](https://github.com/pmndrs/cannon-es-debugger).
+- Added a property `Body.isTrigger : boolean` which, when true allows for the body to trigger collision events without interacting physically with the other colliding bodies.
 
 If instead you're using three.js in a **React** environment with [react-three-fiber](https://github.com/pmndrs/react-three-fiber), check out [use-cannon](https://github.com/pmndrs/use-cannon)! It's a wrapper around cannon-es.
 

diff --git a/screenshots/trigger.png b/screenshots/trigger.png
diff --git a/src/objects/Body.ts b/src/objects/Body.ts
@@ -9,18 +9,18 @@ import type { Material } from '../material/Material'
 import type { World } from '../world/World'
 
 export const BODY_TYPES = {
-  DYNAMIC: 1 as const,
-  STATIC: 2 as const,
-  KINEMATIC: 4 as const,
-}
+  DYNAMIC: 1,
+  STATIC: 2,
+  KINEMATIC: 4,
+} as const
 
 export type BodyType = typeof BODY_TYPES[keyof typeof BODY_TYPES]
 
 export const BODY_SLEEP_STATES = {
-  AWAKE: 0 as const,
-  SLEEPY: 1 as const,
-  SLEEPING: 2 as const,
-}
+  AWAKE: 0,
+  SLEEPY: 1,
+  SLEEPING: 2,
+} as const
 
 export type BodySleepState = typeof BODY_SLEEP_STATES[keyof typeof BODY_SLEEP_STATES]
 
@@ -44,6 +44,7 @@ export type BodyOptions = {
   linearFactor?: Vec3
   angularFactor?: Vec3
   shape?: Shape
+  isTrigger?: boolean
 }
 
 /**
@@ -130,6 +131,7 @@ export class Body extends EventTarget {
   aabbNeedsUpdate: boolean // Indicates if the AABB needs to be updated before use.
   boundingRadius: number // Total bounding radius of the Body including its shapes, relative to body.position.
   wlambda: Vec3
+  isTrigger: boolean // When true "collide" events are still triggered but bodies do not interact.
 
   static idCounter: number
   static COLLIDE_EVENT_NAME: 'collide'
@@ -246,6 +248,7 @@ export class Body extends EventTarget {
     this.aabbNeedsUpdate = true
     this.boundingRadius = 0
     this.wlambda = new Vec3()
+    this.isTrigger = Boolean(options.isTrigger)
 
     if (options.shape) {
       this.addShape(options.shape)

diff --git a/src/solver/Solver.ts b/src/solver/Solver.ts
@@ -34,7 +34,7 @@ export class Solver {
    * @param {Equation} eq
    */
   addEquation(eq: Equation): void {
-    if (eq.enabled) {
+    if (eq.enabled && !eq.bi.isTrigger && !eq.bj.isTrigger) {
       this.equations.push(eq)
     }
   }