WebGLRenderTarget helper for three.js : see the output in realtime in a small canvas
Try it in this jsfiddle
npm install three-rt-helper
and
import RenderTargetHelper from 'three-rt-helper';
or
<script src='https://unpkg.com/three-rt-helper'></script>
const renderTargetHelper = RenderTargetHelper( renderer, myWebGLRenderTarget );
document.body.append( renderTargetHelper );
// in the render loop
renderTargetHelper.update();