examples/light/index.html

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	<head>
		<title>Reticle example</title>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
		<script src="../libs/three/three.min.js"></script>
 		<script module src="../../dist/webxr.js"></script>
		<link rel="stylesheet" href="../common.css"/>
	</head>
	<body>
		<div id="description">
			<h2>Illumination Sensing</h2>
			<h5>(click to dismiss)</h5>
			<p>Place a reticle on surfaces illuminated with an estimate of the light in the room.</p>
		</div>
		<button type=button id=go-button>Go</button>
		<script type=module>
			/*
			Reticle Example shows how to find surfaces or other features and place reticle relative to them.

			In a production application, you would likely want to request world geometry, rather than only 
			using low level hit testing, and fall back to this method if the user declines to provide 
			real world geometry access.
			*/

			// some dependencies and utilities
			import * as mat4 from '../libs/gl-matrix/mat4.js'
			import * as vec3 from '../libs/gl-matrix/vec3.js'

			import XREngine from "../XREngine.js"
			import XRInputManager from "../XRInputManager.js"

			let device = null
			let session = null
			let eyeLevelFrameOfReference = null
			let engine = null
			
			// temporary working variables
			const workingMatrix = mat4.create()
			const workingVec3 = vec3.create()

			var savedOrigin = [0,0,0]
			var savedDirection = [0,0,-1]
			var reticleParent = new THREE.Object3D()
			var reticle = null
			
			var reticleTrackedColor = new THREE.Color( 0xDDFFDD );
			var reticleNotTrackedColor = new THREE.Color( 0xFF6666 );
			var reticleMaterial = new THREE.MeshStandardMaterial({ color: reticleTrackedColor })
			var requestNextHit = true

			var ambientLight = null
			var directionalLight = null

			function initializeScene(){
				ambientLight = engine.addAmbientLight()
				directionalLight = engine.addDirectionalLight()
				// Add a box and axis at the origin of the eye-level coordinate system
				// for debugging by uncommenting these lines
				// engine.addBox([0, 0, 0], [0.025, 0.025, 0.025], 0x44ff44)
				// engine.addAxesHelper([0,0,0], [0.2,0.2,0.2])				
				
				reticle = new THREE.Mesh(
					new THREE.RingGeometry(0.04, 0.05, 36, 64),
					reticleMaterial
				)

				reticle.geometry.applyMatrix(new THREE.Matrix4().makeRotationX(THREE.Math.degToRad(-90)))
				reticleParent.add(reticle)

				reticleParent.matrixAutoUpdate = false
				reticleParent.visible = false
				engine.scene.add(reticleParent)
			}
			
			function updateScene(frame){
				if(frame.worldInformation.estimatedLight){
					let ambientIntensity = frame.worldInformation.estimatedLight.ambientIntensity
					ambientLight.intensity = ambientIntensity;
					directionalLight.intensity = ambientIntensity * 0.5;
				}
			}

			// handle hit testing slightly differently than other samples, since we're doing
			// it per frame.  The "boiler plate" code below is slightly different, setting 
			// requestNextHit on tap instead of executing the hit test.  The custom XREngineHits
			// does a hit test each frame if the previous one has resolved
			function handleHitResults(hits) {
				let size = 0.05;
				if (hits.length > 0) {
					let hit = hits[0]

					session.requestFrameOfReference('head-model').then(headFrameOfReference => {
						// convert hit matrices from head to eye level coordinate systems
						headFrameOfReference.getTransformTo(eyeLevelFrameOfReference, workingMatrix)
						mat4.multiply(workingMatrix, workingMatrix, hit.hitMatrix)

						const node = reticleParent
						node.matrix.fromArray(workingMatrix)
						reticleParent.visible = true   // it starts invisible
						reticle.material.color = reticleTrackedColor

						node.updateMatrixWorld(true)
					})
				} else {
					reticle.material.color = reticleNotTrackedColor
				}
				requestNextHit = true
			}

			class XREngineHits extends XREngine {
				endFrame(){
					if (requestNextHit) {
						requestNextHit = false

						session.requestFrameOfReference('head-model').then(headFrameOfReference => {
							session.requestHitTest(savedOrigin, savedDirection, headFrameOfReference)
								.then(handleHitResults)
								.catch(err => {
									console.error('Error testing hits', err)
								})
						})
					}
				}
			}

			////////////////////////////////////////////////////
			////////////////////////////////////////////////////
			// BOILER PLATE.  Can you feel the plates boiling?
			//
			// There are slight differences between examples but largely this code is similar
			//
			// Create the output context where the XRSession will place composited renders
			const xrCanvas = document.createElement('canvas')
			xrCanvas.setAttribute('class', 'xr-canvas')
			const xrContext = xrCanvas.getContext('xrpresent')
			if(!xrContext){
				console.error('No XR context', xrCanvas)
			}

			// get the XR Device
			navigator.xr.requestDevice().then(xrDevice => {
				device = xrDevice
			}).catch(err => {
			})

			document.getElementById('description').addEventListener('touchstart', hideMe, {capture: true})
			function hideMe(event) { 
				event.target.style.display = 'none' 
				event.stopPropagation()
			}

			document.getElementById('go-button').addEventListener('click', handleStartSessionRequest, true)
			document.getElementById('go-button').addEventListener('touchstart', handleGoButtonTouch, true)
			function handleGoButtonTouch(event) { 
				event.stopPropagation()
			}

			// handle input events from the XRInputManager
			const inputManager = new XRInputManager(handleXRInput)
			function handleXRInput(eventName, details){
				switch(eventName){
					case 'normalized-touch':
						hitTestWithScreenCoordinates(...details.normalizedCoordinates)
						break
					default:
						console.error('unknown xr input event', eventName, details)
						break
				}
			}

			function hitTestWithScreenCoordinates(normalizedX, normalizedY){
				if(session === null){
					console.log('No session for hit testing')
					return
				}

				// Convert the screen coordinates into head-model origin/direction for hit testing
				const [origin, direction] = XRInputManager.convertScreenCoordinatesToRay(normalizedX, normalizedY, 
																							engine.camera.projectionMatrix)
				savedOrigin = origin
				savedDirection = direction

				requestNextHit = true
			}

			/////////////////////
			// Session startup / shutdown
			function handleStartSessionRequest(ev){
				if(device === null){
					console.error('No xr device')
					return
				}

				if (!session) {
					device.requestSession({ 
						outputContext: xrContext,
						worldSensing: true  
					}).then(handleSessionStarted)
						.catch(err => {
							console.error('Session setup error', err)
						})
					document.getElementById('go-button').innerText = "End"
					document.getElementById('go-button').style.display = "none"
				} else {
					session.end()
					handleSessionEnded();
					reticleParent.visible = false   // it starts invisible
					document.getElementById('description').style.display = 'block' 
					document.getElementById('go-button').style.display = "block"
					document.getElementById('go-button').innerText = "Go"
				}
			}

			function handleSessionEnded() {	
				session = null
			}

			function handleSessionStarted(xrSession){
				session = xrSession
				document.body.insertBefore(xrCanvas, document.body.firstChild)

				let sensingState = xrSession.updateWorldSensingState({
					illuminationDetectionState : {
					   enabled : true
					}
				})

				// Create the context where we will render our 3D scene
				const canvas = document.createElement('canvas')
				var glContext = canvas.getContext('webgl', {
					compatibleXRDevice: device
				})
				if(!glContext) throw new Error('Could not create a webgl context')

				// Set up the base layer
				session.baseLayer = new XRWebGLLayer(session, glContext)

				// Create a simple test scene and renderer
				// The engine's scene is in the eye-level coordinate system 
				// Our custom engine class does hit testing at the end of each rAF 
				engine = new XREngineHits(canvas, glContext)

				createRootNode().then(() => {
					// Kick off rendering
					session.requestAnimationFrame(handleAnimationFrame)
				})

				initializeScene()
			}

			async function createRootNode() {
				let headFrameOfReference = await session.requestFrameOfReference('head-model')
				eyeLevelFrameOfReference = await session.requestFrameOfReference('eye-level')

				// get the location of the device, and use it to create an 
				// anchor with the identity orientation
				headFrameOfReference.getTransformTo(eyeLevelFrameOfReference, workingMatrix)
				mat4.getTranslation(workingVec3, workingMatrix)
				mat4.fromTranslation(workingMatrix, workingVec3)

				let anchor = await session.addAnchor(workingMatrix, eyeLevelFrameOfReference)
				engine.addAnchoredNode(anchor, engine.root)
				
				return true
			}

			////////////////
			// render loop			
			function handleAnimationFrame(t, frame){
				updateScene(frame)
				if(!session || session.ended) return
				session.requestAnimationFrame(handleAnimationFrame)

				let pose = frame.getDevicePose(eyeLevelFrameOfReference)
				if(!pose){
					console.log('No pose')
					return
				}

				engine.startFrame()
				for (let view of frame.views) {
					engine.preRender(
						session.baseLayer.getViewport(view),
						view.projectionMatrix,
						pose.getViewMatrix(view)
					)
					engine.render()
				}
				engine.endFrame()
			}

		</script>
	</body>
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