JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdn.jsdelivr.net/npm/[email protected]/build/three.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/[email protected]/examples/js/shaders/HorizontalBlurShader.js"></script>
<script src="https://cdn.jsdelivr.net/npm/[email protected]/examples/js/shaders/VerticalBlurShader.js"></script>

CSS

body {
	  margin: 0;
}

JavaScript

let camera, scene, renderer;

init().then( render );

async function init() {

  camera = new THREE.PerspectiveCamera(70, window.innerWidth / window.innerHeight, 0.01, 10);
  camera.position.z = 3;

  scene = new THREE.Scene();
  
  renderer = new THREE.WebGLRenderer({
    antialias: true
  });
  renderer.setPixelRatio(window.devicePixelRatio);
  renderer.setSize(window.innerWidth, window.innerHeight);
  document.body.appendChild(renderer.domElement);


  const loader = new THREE.TextureLoader();
  const texture = await loader.loadAsync('https://threejs.org/examples/textures/uv_grid_opengl.jpg');
  //scene.background = texture;

  scene.background = blurTexture( texture );

}

function blurTexture(texture) {

	const width = texture.image.width;
  const height = texture.image.height;

  const cameraRTT = new THREE.OrthographicCamera(-1, 1, 1, -1, 0, 1);
  const sceneRTT = new THREE.Scene();

  // render targets

  const renderTargetTemp = new THREE.WebGLRenderTarget(width, height);
  const renderTargetFinal = new THREE.WebGLRenderTarget(width, height);

  // shader materials

  const hBlurMaterial = new THREE.ShaderMaterial({
    vertexShader: THREE.HorizontalBlurShader.vertexShader,
    fragmentShader: THREE.HorizontalBlurShader.fragmentShader,
    uniforms: THREE.UniformsUtils.clone(THREE.HorizontalBlurShader.uniforms)
  });

  hBlurMaterial.uniforms.tDiffuse.value = texture;
  hBlurMaterial.uniforms.h.value = 1 / width;

  const vBlurMaterial = new THREE.ShaderMaterial({
    vertexShader: THREE.VerticalBlurShader.vertexShader,
    fragmentShader: THREE.VerticalBlurShader.fragmentShader,
    uniforms: THREE.UniformsUtils.clone(THREE.VerticalBlurShader.uniforms)
  });

  vBlurMaterial.uniforms.tDiffuse.value = renderTargetTemp.texture;
  vBlurMaterial.uniforms.v.value = 1 / height;

  // fullscreen quad

  const planeGeometry = new THREE.PlaneGeometry(2, 2);

  const fullScreenQuad = new THREE.Mesh(planeGeometry, hBlurMaterial);
  sceneRTT.add(fullScreenQuad);

 ...