Particle/Plane classes

by jmcjc5u

HTML

<div id="info">finite plane
</div>

CSS

#info {
  position: absolute;
  top: 0px;
  width: 100%;
  padding: 10px;
  text-align: center;
  color: #ffff00
}

body {
  overflow: hidden;
}

JavaScript

import * as THREE from "https://threejs.org/build/three.module.js";
javascript:(function(){var script=document.createElement('script');script.onload=function(){var stats=new Stats();document.body.appendChild(stats.dom);requestAnimationFrame(function loop(){stats.update();requestAnimationFrame(loop)});};script.src='https://mrdoob.github.io/stats.js/build/stats.min.js';document.head.appendChild(script);})()

class Particle {
	constructor (mesh) {
  	this.pos = new THREE.Vector3()
    this.vel = new THREE.Vector3()
    this.force = new THREE.Vector3(0,-10,0)
    this.mesh = mesh;
    scene.add (mesh)
  }
  
  update (dt) {
		this.vel.add (this.force.clone().multiplyScalar (dt))
  	this.pos.add (this.vel.clone().multiplyScalar(dt))

		// collision with planes
    this.collidingPlanes (planes);
    
		this.mesh.position.copy (this.pos)
  }
  
	collidingPlanes (planes) {
    const EPS = 1e-3
    const CR = 0.99
  	for (let i = 0; i < planes.length; i++) {
			let plane = planes[i]
			let point = this.pos.clone().sub (plane.ptOnPl)
      if ( point.dot(plane.normal) < EPS 
      && point.projectOnPlane (plane.normal).length() < plane.length/2) {
				// position correction
      	this.pos.copy (plane.ptOnPl.clone().add (point.projectOnPlane(plane.normal)) )
      	// velocity update
      	this.vel.sub (plane.normal.clone().multiplyScalar ((1+CR)*this.vel.dot(plane.normal)))
      	return;  // assume particle collides with AT MOST one plane
      }
  	}
  }

}

class FinitePlane {
	constructor (localPointOnPlane, localNormal, mesh, length) {
    this.localPtOnPl = localPointOnPlane.clone();
		this.localNormal = localNormal.clone();
    this.mesh = mesh;  // the graphics representation
    scene.add (mesh)
    this.length = length || 1e10;  // if not set, treat as infinite plane
  }
  update () {
  	this.mesh.updateMatrixWorld() // important!
  	this.ptOnPl = this.mesh.localToWorld (this.localPtOnPl.clone());
    let normalMat = new THREE.Matrix3().getNormalMatrix...