Frame differencing pass for THREE.EffectComposer

diff.frag

varying vec3 pos;
uniform sampler2D cameraBuffer;
uniform sampler2D lastCameraBuffer;

void main () {
  vec2 texCoord = .5 + pos.xy * .5;

  vec3 cameraColor = texture2D(cameraBuffer, texCoord).rgb;
  vec3 lastCameraColor = texture2D(lastCameraBuffer, texCoord).rgb;

  float diffColor = distance(cameraColor, lastCameraColor);

  vec3 color = vec3(diffColor);

  gl_FragColor = vec4(color, 1.0);
}

diff.vert

varying vec3 pos;

void main () {
	pos = position.xyz;

  gl_Position = projectionMatrix * modelViewMatrix * vec4(position.xyz, 1.0);
}

DifferencePass.js

import { Pass, RenderPass } from 'postprocessing';
const glslify = require('glslify');
const path = require('path');

export default class DifferencePass extends Pass {
  constructor() {
    super("DifferencePass");

    this.bufferTexture = new THREE.WebGLRenderTarget( window.innerWidth, window.innerHeight, { minFilter: THREE.LinearFilter, magFilter: THREE.NearestFilter});
    this.renderPassLastBuffer = new RenderPass(this.scene, this.camera);
    
    this.quad.material = new THREE.ShaderMaterial({
      vertexShader: glslify(path.resolve(__dirname, '../shaders/diff.vert')),
      fragmentShader: glslify(path.resolve(__dirname, '../shaders/diff.frag')),
      uniforms: {
        time: { value: 0 },
        cameraBuffer: { value: null, type: 't' },
        lastCameraBuffer: { value: this.bufferTexture.texture, type: 't' }
      }
    });
  }

  render(renderer, inputBuffer, outputBuffer, delta, stencilTest) {
    this.material.uniforms.cameraBuffer.value = inputBuffer.texture;

    renderer.render(this.scene, this.camera, this.renderToScreen ? null : outputBuffer);

    this.renderPassLastBuffer.render(renderer, this.bufferTexture);
    this.bufferTexture.needsUpdate = true;
  }
}