three.js/manual/examples/shared-picking.js

import * as THREE from 'https://cdn.skypack.dev/three@0.136.0/build/three.module.js';

export const state = {
	width: 300, // canvas default
	height: 150, // canvas default
};

export const pickPosition = { x: 0, y: 0 };

export function init( data ) { // eslint-disable-line no-unused-vars

	const { canvas } = data;
	const renderer = new THREE.WebGLRenderer( { antialias: true, canvas } );

	state.width = canvas.width;
	state.height = canvas.height;

	const fov = 75;
	const aspect = 2; // the canvas default
	const near = 0.1;
	const far = 100;
	const camera = new THREE.PerspectiveCamera( fov, aspect, near, far );
	camera.position.z = 4;

	const scene = new THREE.Scene();

	{

		const color = 0xFFFFFF;
		const intensity = 1;
		const light = new THREE.DirectionalLight( color, intensity );
		light.position.set( - 1, 2, 4 );
		scene.add( light );

	}

	const boxWidth = 1;
	const boxHeight = 1;
	const boxDepth = 1;
	const geometry = new THREE.BoxGeometry( boxWidth, boxHeight, boxDepth );

	function makeInstance( geometry, color, x ) {

		const material = new THREE.MeshPhongMaterial( {
			color,
		} );

		const cube = new THREE.Mesh( geometry, material );
		scene.add( cube );

		cube.position.x = x;

		return cube;

	}

	const cubes = [
		makeInstance( geometry, 0x44aa88, 0 ),
		makeInstance( geometry, 0x8844aa, - 2 ),
		makeInstance( geometry, 0xaa8844, 2 ),
	];

	class PickHelper {

		constructor() {

			this.raycaster = new THREE.Raycaster();
			this.pickedObject = null;
			this.pickedObjectSavedColor = 0;

		}
		pick( normalizedPosition, scene, camera, time ) {

			// restore the color if there is a picked object
			if ( this.pickedObject ) {

				this.pickedObject.material.emissive.setHex( this.pickedObjectSavedColor );
				this.pickedObject = undefined;

			}

			// cast a ray through the frustum
			this.raycaster.setFromCamera( normalizedPosition, camera );
			// get the list of objects the ray intersected
			const intersectedObjects = this.raycaster.intersectObjects( scene.children );
			if ( intersectedObjects.length ) {

				// pick the first object. It's the closest one
				this.pickedObject = intersectedObjects[ 0 ].object;
				// save its color
				this.pickedObjectSavedColor = this.pickedObject.material.emissive.getHex();
				// set its emissive color to flashing red/yellow
				this.pickedObject.material.emissive.setHex( ( time * 8 ) % 2 > 1 ? 0xFFFF00 : 0xFF0000 );

			}

		}

	}

	const pickHelper = new PickHelper();

	function resizeRendererToDisplaySize( renderer ) {

		const canvas = renderer.domElement;
		const width = state.width;
		const height = state.height;
		const needResize = canvas.width !== width || canvas.height !== height;
		if ( needResize ) {

			renderer.setSize( width, height, false );

		}

		return needResize;

	}

	function render( time ) {

		time *= 0.001;

		if ( resizeRendererToDisplaySize( renderer ) ) {

			camera.aspect = state.width / state.height;
			camera.updateProjectionMatrix();

		}

		cubes.forEach( ( cube, ndx ) => {

			const speed = 1 + ndx * .1;
			const rot = time * speed;
			cube.rotation.x = rot;
			cube.rotation.y = rot;

		} );

		pickHelper.pick( pickPosition, scene, camera, time );

		renderer.render( scene, camera );

		requestAnimationFrame( render );

	}

	requestAnimationFrame( render );

}