How to get texture color at intersection with Raycast?

Questions
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8

New code. To calculate pages scrolling coordinates:

<!DOCTYPE html>
<html lang="en">
	<head>
		<title>three.js webgl - cameras</title>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">

	</head>
	<body>


		<script type="importmap">
			{
				"imports": {
					"three": "../build/three.module.js"
				}
			}
		</script>



		<script id="fragment_shader_screen" type="x-shader/x-fragment">

			varying vec2 vUv;
			uniform sampler2D tDiffuse;

			void main() {

				gl_FragColor = texture2D( tDiffuse, vUv );

			}

		</script>

		<script id="vertexShader" type="x-shader/x-vertex">

			varying vec2 vUv;

			void main() {

				vUv = uv;
				gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );

			}

		</script>



		<script type="module">

import * as THREE from 'three';
  import { OrbitControls } from "./jsm/controls/OrbitControls.js";

  let width = window.innerWidth,
    height = window.innerHeight;

  //initialize renderer
  let renderer = new THREE.WebGLRenderer();
  renderer.setSize(width, height);
  renderer.autoClear = false;
  document.body.appendChild(renderer.domElement);

  //scene / raycaster / camera / controls
  let scene = new THREE.Scene();


let cameraRTT = new THREE.OrthographicCamera( window.innerWidth / - 2, window.innerWidth / 2, window.innerHeight / 2, window.innerHeight / - 2, - 10000, 10000 );
cameraRTT.position.z = 100;


let sceneScreen = new THREE.Scene();


let renderTargetTexture = new THREE.WebGLRenderTarget(
window.innerWidth, window.innerHeight, { minFilter: THREE.LinearFilter, magFilter: THREE.NearestFilter, format: THREE.RGBAFormat, type: THREE.FloatType }
);
const materialScreen = new THREE.ShaderMaterial( {

uniforms: { 'tDiffuse': { value: renderTargetTexture.texture } },
vertexShader: document.getElementById( 'vertexShader' ).textContent,
fragmentShader: document.getElementById( 'fragment_shader_screen' ).textContent,
depthWrite: false
	} );

  const plane = new THREE.PlaneGeometry( window.innerWidth, window.innerHeight );
  let quad = new THREE.Mesh(plane,materialScreen );
				quad.position.z = - 100;
				sceneScreen.add( quad );


  let rayCaster = new THREE.Raycaster();
  let camera = new THREE.PerspectiveCamera(45, width / height, 0.1, 10000);
  camera.position.copy(new THREE.Vector3(100, 100, 100));
  camera.lookAt(new THREE.Vector3(0, 0, 0));
  scene.add(camera);
  let controls = new OrbitControls(camera, renderer.domElement);

  // global variables
  let mouse = new THREE.Vector2();
  let planeMesh;
  let textureData;

  let imgPath =
    "https://cdn.pixabay.com/photo/2022/05/23/13/16/bird-7216181_1280.jpg";

  //load texture and initialize planeMesh, textureData and renderTargetTexture
  new THREE.TextureLoader().load(imgPath, function (texture) {
    textureData = texture;

    planeMesh = new THREE.Mesh(
      new THREE.PlaneGeometry(texture.image.width, texture.image.height),
      new THREE.MeshBasicMaterial({ map: texture })
    );

    scene.add(planeMesh);


    
  });


resize();
animate();


function resize() {
renderer.setSize(width,height);
camera.aspect=width/height;
camera.updateProjectionMatrix();
}


function animate() {
renderer.clear();
renderer.render(scene,camera);
requestAnimationFrame(animate);
controls.update();
}


window.addEventListener("resize", resize);


window.addEventListener("pointerup", (event) => {


var scrollLeft=window.pageXOffset || document.documentElement.scrollLeft;
var scrollTop=window.pageYOffset || document.documentElement.scrollTop;


mouse.x =((event.clientX-renderer.domElement.offsetLeft+scrollLeft)/renderer.domElement.width)*2-1;
mouse.y =-((event.clientY-renderer.domElement.offsetTop+scrollTop)/renderer.domElement.height)*2+1;


rayCaster.setFromCamera(mouse, camera);
let intersections = rayCaster.intersectObject(planeMesh);


if(intersections.length>0){


mouse.x=parseInt(renderer.domElement.width/2+mouse.x*renderer.domElement.width/2);
mouse.y=parseInt(renderer.domElement.height/2+mouse.y*renderer.domElement.height/2);


renderer.clear();
renderer.setRenderTarget(renderTargetTexture);
renderer.clear();
renderer.render(scene,camera);
renderer.setRenderTarget(null);
renderer.render(sceneScreen,cameraRTT);
const read=new Float32Array(4);
renderer.readRenderTargetPixels(renderTargetTexture,mouse.x,mouse.y,1,1,read);
let r=parseInt(read[0]*255);
let g=parseInt(read[1]*255);
let b=parseInt(read[2]*255);
console.log("X:"+mouse.x+" Y:"+mouse.y+" RGB: ["+r+","+g+","+b+"] Color: %c     ","background:rgb("+r+","+g+","+b+");");


}
});

</script>

	</body>
</html>