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I am currently using react-three-fiber to make scene but I don't know how to put 3D objects at different random positions. I have used a for loop inside useFrame to have different random positions, but as this will render every time, particles will just move to random position again. But I want these positions to be random only at intialization and then just move the whole mesh. But if I use for loop just before the useframe it is giving error-"Cannot read property 'setMatrixAt' of undefined". PS- I am just tring to recreate -https://threejs.org/examples/?q=postprocessing#webgl_postprocessing

import * as THREE from 'three'
import ReactDOM from 'react-dom'
import React, { useRef, useMemo, useState, useEffect } from 'react'
import { Canvas, useFrame } from 'react-three-fiber'
import Effects from './Effects'
import './styles.css'
const tempObject = new THREE.Object3D()

function Boxes({count}) {
  
  const ref = useRef()
  const previous = useRef()

  const particles = useMemo(() => {
    const temp = []
   

  useFrame(state => {
    const time = state.clock.getElapsedTime()
    ref.current.rotation.x += 0.00000
    ref.current.rotation.y += 0.00000
    let i = 0
    for (let x = 0; x < count; x++){
      const id = i++
      tempObject.position.set(Math.random() - 0.5, Math.random() - 0.5, Math.random() - 0.5 ).normalize()
      tempObject.position.multiplyScalar( Math.random() * 40 )
      tempObject.rotation.set( Math.random() * 2, Math.random() * 2, Math.random() * 2 )
      tempObject.updateMatrix()
      ref.current.setMatrixAt(id, tempObject.matrix)
    }
    ref.current.instanceMatrix.needsUpdate = true
  })

  return (
    <instancedMesh ref={ref} args={[null, null, count]}  >
      <sphereBufferGeometry attach="geometry" args={[1, 4, 4]}/>  
      <meshPhongMaterial attach="material" color="#ffffff" flatShading ="true"/>
    </instancedMesh>
  )
}

ReactDOM.render(
  <Canvas
    gl={{ antialias: false, alpha: false }}
    camera={{ position: [0, 0, 400], near: 5, far: 1000 }}
    onCreated={({ gl }) => gl.setClearColor('pink')}>
    <ambientLight intensity={1.1} color="#222222" />
    <directionalLight color="#ffffff" position={[1, 1, 1]} />
    <Boxes count={1000}/>
    <Effects />
  </Canvas>,
  document.getElementById('root')
)
prinzu
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1 Answers1

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I had the same issue, your code seems well, the problem is when you are trying to bind the instancedMesh with ref, I don't know why is not working well the binding with old react version, but I fixed it upgrading the react and react-dom package from ^16.9.0 to 16.10.2 version.

user124391
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