Add floor anchor API and update the examples to use it.

examples/ar_anchors/index.html

@@ -46,7 +46,6 @@
 				constructor(domElement){
 					super(domElement, false)
 					this.anchorsToAdd = [] // { node, x, y, z }
-					this.anchoredNodes = [] // { anchorUID, node }
 
 					this.addObjectButton = document.createElement('button')
 					this.addObjectButton.setAttribute('class', 'add-object-button')
@@ -87,7 +86,7 @@
 					const headCoordinateSystem = frame.getCoordinateSystem(XRCoordinateSystem.HEAD_MODEL)
 					const trackerCoordinateSystem = frame.getCoordinateSystem(XRCoordinateSystem.TRACKER)
 
-					// Create anchors for newly anchored nodes
+					// Create anchors and start tracking them
 					for(let anchorToAdd of this.anchorsToAdd){
 						// Create an anchor that we'd like to add, relative to the current head position
 						const anchorCoordinates = new XRCoordinates(
@@ -97,27 +96,11 @@
 						)
 						const anchor = new XRAnchor(anchorCoordinates)
 
-						// Add and store the anchor UID along with the node that will be updated with changing anchor data
+						// Create the anchor and tell the base class to update the node with its position
 						const anchorUID = frame.addAnchor(anchor)
-						this.anchoredNodes.push({
-							anchorUID: anchorUID,
-							node: anchorToAdd.node
-						})
-						this.scene.add(anchorToAdd.node)
+						this.addAnchoredNode(new XRAnchorOffset(anchorUID), anchorToAdd.node)
 					}
 					this.anchorsToAdd = []
-					
-					// Update anchored node positions in the scene graph
-					for(let anchoredNode of this.anchoredNodes){
-						const anchor = frame.getAnchor(anchoredNode.anchorUID)
-						if(anchor === null){
-							console.error('Unknown anchor ID', anchoredNode.anchorId)
-						} else {
-							anchoredNode.node.matrixAutoUpdate = false
-							anchoredNode.node.matrix.fromArray(anchor.coordinates.getTransformedCoordinates(trackerCoordinateSystem).poseMatrix)
-							anchoredNode.node.updateMatrixWorld(true)
-						}
-					}
 				}
 			}
 

examples/ar_simplest/index.html

@@ -55,27 +55,22 @@
 					})
 					const mesh = new THREE.Mesh(geometry, material)
 					mesh.position.set(0, 1.4, -1)
-					this.scene.add(mesh)
+					this.floorGroup.add(mesh)
 
-					// Add a box at the scene origin
+					// Add a box on the floor
 					const box = new THREE.Mesh(
 						new THREE.BoxBufferGeometry(0.1, 0.1, 0.1),
 						new THREE.MeshPhongMaterial({ color: '#DDFFDD' })
 					)
 					box.position.set(0, 0, 0)
-					this.scene.add(box)
+					this.floorGroup.add(box)
 
+					// Add some lights to the scene
 					this.scene.add(new THREE.AmbientLight('#FFF', 0.2))
 					const directionalLight = new THREE.DirectionalLight('#FFF', 0.6)
 					directionalLight.position.set(0, 10, 0)
 					this.scene.add(directionalLight)
 				}
-
-				// Called once per frame, before render to give the app a chance to update the this.scene
-				updateScene(frame){
-					// Uncomment the next line to spin the teapot
-					//this.scene.children[0].rotation.y += 0.01
-				}
 			}
 
 

examples/common.js

@@ -1,6 +1,8 @@
 /*
 	XRExampleBase holds all of the common XR setup, rendering, and teardown code for a THREE.js based app
-	Extending classes should be able to focus on rendering their scene
+	It also holds a list of THREE nodes and XRAnchorOffsets which it uses to update the nodes' poses
+
+	Extending classes should be able to focus mainly on rendering their scene and handling user input
 
 	Parameters:
 		domElement: an element used to show error messages
@@ -17,6 +19,8 @@ class XRExampleBase {
 		this.createVirtualReality = createVirtualReality
 		this.shouldStartPresenting = shouldStartPresenting
 
+		this._boundHandleFrame = this._handleFrame.bind(this) // Useful for setting up the requestAnimationFrame callback
+
 		// Set during the XR.getDisplays call below
 		this.displays = null
 
@@ -30,6 +34,12 @@ class XRExampleBase {
 		this.camera = new THREE.PerspectiveCamera(70, 1024, 1024, 0.1, 1000) // These values will be overwritten by the projection matrix from ARKit or ARCore
 		this.renderer = null // Set in this.handleNewSession
 
+		this.requestedFloor = false
+		this.floorGroup = new THREE.Group() // This group will eventually be be anchored to the floor (see findFloorAnchor below)
+
+		// an array of info that we'll use in _handleFrame to update the nodes using anchors
+		this.anchoredNodes = [] // { XRAnchorOffset, Three.js Object3D }
+
 		// Give extending classes the opportunity to initially populate the scene
 		this.initializeScene()
 
@@ -141,7 +151,7 @@ class XRExampleBase {
 		this.renderer.autoClear = false
 		this.renderer.setClearColor('#000', 0)
 
-		this.session.requestFrame(frame => { this.handleFrame(frame) })
+		this.session.requestFrame(this._boundHandleFrame)
 	}
 
 	// Extending classes can react to these events
@@ -161,9 +171,28 @@ class XRExampleBase {
 	*/
 	updateScene(frame){}
 
-	handleFrame(frame){
-		const nextFrameRequest = this.session.requestFrame(frame => { this.handleFrame(frame) })
-		let headPose = frame.getViewPose(frame.getCoordinateSystem(XRCoordinateSystem.HEAD_MODEL))
+	_handleFrame(frame){
+		const nextFrameRequest = this.session.requestFrame(this._boundHandleFrame)
+		const headPose = frame.getViewPose(frame.getCoordinateSystem(XRCoordinateSystem.HEAD_MODEL))
+
+		// If we haven't already, request the floor anchor offset
+		if(this.requestedFloor === false){
+			this.requestedFloor = true
+			frame.findFloorAnchor('first-floor-anchor').then(anchorOffset => {
+				if(anchorOffset === null){
+					console.error('could not find the floor anchor')
+					return
+				}
+				this.addAnchoredNode(anchorOffset, this.floorGroup)
+			}).catch(err => {
+				console.error('error finding the floor anchor', err)
+			})
+		}
+
+		// Update anchored node positions in the scene graph
+		for(let anchoredNode of this.anchoredNodes){
+			this.updateNodeFromAnchorOffset(frame, anchoredNode.node, anchoredNode.anchorOffset)
+		}
 
 		// Let the extending class update the scene before each render
 		this.updateScene(frame)
@@ -190,6 +219,39 @@ class XRExampleBase {
 			this.renderer.render(this.scene, this.camera)
 		}
 	}
+
+	/*
+	Add a node to the scene and keep its pose updated using the anchorOffset
+	*/
+	addAnchoredNode(anchorOffset, node){
+		this.anchoredNodes.push({
+			anchorOffset: anchorOffset,
+			node: node
+		})
+		this.scene.add(node)
+	}
+
+	/*
+	Get the anchor data from the frame and use it and the anchor offset to update the pose of the node, this must be an Object3D
+	*/
+	updateNodeFromAnchorOffset(frame, node, anchorOffset){
+		const anchor = frame.getAnchor(anchorOffset.anchorUID)
+		if(anchor === null){
+			throttledConsoleLog('Unknown anchor uid', anchorOffset.anchorUID)
+			return
+		}
+
+		node.matrixAutoUpdate = false
+		const offsetCoordinates = anchorOffset.getTransformedCoordinates(anchor)
+		if(offsetCoordinates.coordinateSystem.type === XRCoordinateSystem.TRACKER){
+			node.matrix.fromArray(offsetCoordinates.poseMatrix)
+		} else {
+			node.matrix.fromArray(
+				offsetCoordinates.getTransformedCoordinates(frame.getCoordinateSystem(XRCoordinateSystem.TRACKER)).poseMatrix
+			)
+		}
+		node.updateMatrixWorld(true)
+	}
 }
 
 function fillInGLTFScene(path, scene, position=[0, 0, -2], scale=[1, 1, 1]){

examples/hit_test/index.html

@@ -49,8 +49,6 @@
 					super(domElement, false)
 					this._tapEventData = null // Will be filled in on touch start and used in updateScene
 
-					this.anchoredNodes = [] // { XRAnchorOffset, Three.js Object3D }
-
 					// A message at the bottom of the screen that shows whether a surface has been found
 					this._messageEl = document.createElement('div')
 					this.el.appendChild(this._messageEl)
@@ -71,15 +69,7 @@
 						new THREE.MeshPhongMaterial({ color: '#DDFFDD' })
 					)
 					box.position.set(0, 0, 0)
-					this.scene.add(box)
-
-					// Add a box one meter in front of scene origin to show the direction of the Z axis
-					box = new THREE.Mesh(
-						new THREE.BoxBufferGeometry(0.1, 0.1, 0.1),
-						new THREE.MeshPhongMaterial({ color: '#FF0000' })
-					)
-					box.position.set(0, 0, -1)
-					this.scene.add(box)
+					this.floorGroup.add(box)
 
 					// Add a few lights
 					this.scene.add(new THREE.AmbientLight('#FFF', 0.2))
@@ -100,46 +90,13 @@
 							if(anchorOffset === null){
 								this._messageEl.innerHTML = 'miss'
 							} else {
-								const anchor = frame.getAnchor(anchorOffset.anchorUID)
-								if(anchor === null){
-									console.error('unknown anchor uid', anchorOffset.anchorUID)
-									return
-								}
-								this._messageEl.innerHTML = 'hit: ' + anchor.coordinates.position.join(', ')
-
-								// Save the XRAnchorOffset and the node so that we can update the node's position based off of the anchor
-								let anchorInfo = {
-									anchorOffset: anchorOffset,
-									node: this._createSceneGraphNode()
-								}
-								this.anchoredNodes.push(anchorInfo)
-
-								// Add a block to the scene to indicate the position of the XRAnchorOffset
-								// Its position will be updated below along with the other anchored nodes
-								this.scene.add(anchorInfo.node)
+								this._messageEl.innerHTML = 'hit'
+								this.addAnchoredNode(anchorOffset, this._createSceneGraphNode())
 							}
 						}).catch(err => {
 							console.error('Error in hit test', err)
 						})
 					}
-
-					const trackerCoordinateSystem = frame.getCoordinateSystem(XRCoordinateSystem.TRACKER)
-					// Update anchored node positions in the scene graph using updated anchor positions
-					for(let anchoredNode of this.anchoredNodes){
-						const anchor = frame.getAnchor(anchoredNode.anchorOffset.anchorUID)
-						if(anchor === null){
-							throttledConsoleLog('Unknown anchor uid', anchoredNode.anchorOffset.anchorUID)
-						} else {
-							anchoredNode.node.matrixAutoUpdate = false
-							let offsetCoordinates = anchoredNode.anchorOffset.getTransformedCoordinates(anchor)
-							if(offsetCoordinates.coordinateSystem.type === XRCoordinateSystem.TRACKER){
-								anchoredNode.node.matrix.fromArray(offsetCoordinates.poseMatrix)
-							} else {
-								anchoredNode.node.matrix.fromArray(offsetCoordinates.getTransformedCoordinates(trackerCoordinateSystem).poseMatrix)
-							}
-							anchoredNode.node.updateMatrixWorld(true)
-						}
-					}
 				}
 
 				// Save screen taps as normalized coordinates for use in this.updateScene

polyfill/Reality.js

@@ -60,6 +60,25 @@ export default class Reality extends EventHandlerBase {
 		throw new Error('Exending classes should implement _findAnchor')
 	}
 
+	/*
+	Find an XRAnchorOffset that is at floor level below the current head pose
+	returns a Promise that resolves either to an AnchorOffset or null if the floor level is unknown
+	*/
+	_findFloorAnchor(display, uid=null){
+		// Copy the head model matrix for the current pose so we have it in the promise below
+		const headModelMatrix = new Float32Array(display._headPose.poseModelMatrix)
+
+		return new Promise((resolve, reject) => {
+			// For now, just create an anchor at origin level. Maybe in the future search for a surface?
+			const coordinates = new XRCoordinates(display, display._trackerCoordinateSystem)
+			headModelMatrix[13] = 0 // Set height to 0
+			coordinates.poseMatrix = headModelMatrix
+			const anchor = new XRAnchor(coordinates, uid)
+			this._addAnchor(anchor, display)
+			resolve(new XRAnchorOffset(anchor.uid))
+		})
+	}
+
 	_getAnchor(uid){
 		return this._anchors.get(uid) || null
 	}

polyfill/XRPresentationFrame.js

@@ -61,6 +61,15 @@ export default class XRPresentationFrame {
 		return this._session.reality._findAnchor(normalizedScreenX, normalizedScreenY, this._session.display)
 	}
 
+	/*
+	Find an XRAnchorOffset that is at floor level below the current head pose
+	uid will be the resulting anchor uid (if any), or if null one will be assigned
+	*/
+	findFloorAnchor(uid=null){
+		// Promise<XRAnchorOffset?> findFloorAnchor();
+		return this._session.reality._findFloorAnchor(this._session.display, uid)
+	}
+
 	removeAnchor(uid){
 		// void removeAnchor(DOMString uid);
 		return this._session.reality._removeAnchor(uid)