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<html>
<!-- Any copyright is dedicated to the Public Domain.
http://creativecommons.org/publicdomain/zero/1.0/
-->
<head>
<title>Hit test 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>
<link rel="stylesheet" href="../common.css"/>
</head>
<body>
<div id="description">
<h2>Hit Test Anchors</h2>
<p>Anchor boxes by create XRAnchors from XRHitTest results.</p>
</div>
<button type=button id=go-button disabled>Go</button>
<script type=module>
// 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';
let session = null;
let viewerReferenceSpace = null;
let localReferenceSpace = null;
let engine = null;
let hitTestSource = null;
let inputSource = null;
let hitTestSourceFrameNum = 0;
let isSelecting = false;
// temporary working variables
const workingMatrix = mat4.create();
const workingVec3 = vec3.create();
const goButton = document.getElementById('go-button');
const initXR = () => {
if (navigator.xr) {
navigator.xr.isSessionSupported('immersive-ar').then(supported => {
if (supported) {
goButton.disabled = false;
goButton.addEventListener('click', onButtonClick);
} else {
goButton.initText = 'No WebXR AR support';
}
});
} else {
goButton.initText = 'No WebXR support';
}
};
const onButtonClick = event => {
if (!session) {
navigator.xr.requestSession('immersive-ar', {requiredFeatures: ['hit-test']})
.then(xrSession => {
initSession(xrSession);
goButton.innerText = 'End';
}).catch(err => {
console.error('Session setup error', err);
});
} else {
session.end();
}
};
const initSession = async xrSession => {
session = xrSession;
session.addEventListener('end', onSessionEnd);
session.addEventListener('select', onSelect);
session.addEventListener('inputsourceschange', onInputSourcesChange);
localReferenceSpace = await session.requestReferenceSpace('local');
viewerReferenceSpace = await session.requestReferenceSpace('viewer');
// Create the context where we will render our 3D scene
const canvas = document.createElement('canvas');
const context = canvas.getContext('webgl', {
xrCompatible: true
});
if (!context) throw new Error('Could not create a webgl context');
// Set up the base layer
session.updateRenderState({baseLayer: new XRWebGLLayer(session, context)});
// Create a simple test scene and renderer
// The engine's scene is in the eye-level coordinate system
engine = new XREngine(canvas, context);
// get the location of the device, and use it to create an
// anchor with the identity orientation
session.requestAnimationFrame(async (t, frame) => {
mat4.copy(workingMatrix, frame.getPose(localReferenceSpace, viewerReferenceSpace).transform.matrix);
mat4.getTranslation(workingVec3, workingMatrix);
mat4.fromTranslation(workingMatrix, workingVec3);
const anchor = await frame.addAnchor(workingMatrix, localReferenceSpace);
engine.addAnchoredNode(anchor, engine.root);
// Kick off rendering
session.requestAnimationFrame(handleAnimationFrame);
});
// initialize scene
engine.addAmbientLight();
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])
};
const onSessionEnd = event => {
clearHitTestSource();
session = null;
inputSource = null;
viewerReferenceSpace = null;
localReferenceSpace = null;
goButton.innerText = 'Go';
};
const onInputSourcesChange = event => {
if (inputSource && event.removed.includes(inputSource)) {
inputSource = null;
}
if (!inputSource && event.added.length > 0) {
inputSource = event.added[0];
}
};
const onSelect = event => {
clearHitTestSource();
isSelecting = true;
};
const clearHitTestSource = () => {
if (hitTestSource) {
hitTestSource.cancel();
}
hitTestSource = null;
hitTestSourceFrameNum = 0;
};
// Creates a box used to indicate the location of an anchor offset
const createBox = () => {
const group = new THREE.Group();
const geometry = new THREE.BoxBufferGeometry(0.1, 0.1, 0.1);
const color = new THREE.Color(0xffffff);
color.setHex(Math.random() * 0xffffff);
const material = new THREE.MeshPhongMaterial({color: color});
const mesh = new THREE.Mesh(geometry, material);
const outlineMaterial = new THREE.MeshBasicMaterial({color: 0x00ff00, side: THREE.BackSide});
const outlineMesh = new THREE.Mesh(geometry, outlineMaterial);
mesh.position.set(0, 0.05, 0);
outlineMesh.position.set(0, 0.05, 0);
outlineMesh.scale.multiplyScalar(1.05);
group.add(mesh);
group.add(outlineMesh);
return group;
};
// Create offset ray for hit test from the relative transform
// between viewerPose and inputPose. There may be a room to optimize.
const createOffsetRay = (viewerPose, inputPose) => {
const offsetMatrix = mat4.multiply(mat4.create(), viewerPose.transform.matrix, inputPose.transform.matrix);
const direction = vec3.fromValues(0.0, 0.0, -0.2);
vec3.transformMat4(direction, direction, offsetMatrix);
vec3.normalize(direction, direction);
const offsetDirection = {
x: direction[0],
y: direction[1],
z: direction[2],
w: 0.0
};
const offsetOrigin = {x: 0, y: 0, z: 0, w: 1.0};
return new XRRay(offsetOrigin, offsetDirection);
};
// render loop
const handleAnimationFrame = (t, frame) => {
if (!session || session.ended) return;
session.requestAnimationFrame(handleAnimationFrame);
const viewerPose = frame.getViewerPose(localReferenceSpace);
if (!viewerPose) {
console.log('No viewer pose');
return;
}
// Create HitTest Source. Calculating offset ray from the relative transform
// between viewerPose and inputPose so we need to do in animation frame.
if (isSelecting && inputSource) {
const inputPose = frame.getPose(inputSource.targetRaySpace, localReferenceSpace);
const offsetRay = createOffsetRay(viewerPose, inputPose);
session.requestHitTestSource({space: viewerReferenceSpace, offsetRay: offsetRay}).then(xrHitTestSource => {
hitTestSource = xrHitTestSource;
hitTestSourceFrameNum = 0;
});
isSelecting = false;
}
if (hitTestSource) {
const results = frame.getHitTestResults(hitTestSource);
if (results.length > 0) {
const result = results[0];
const pose = result.getPose(localReferenceSpace);
if (pose) {
frame.addAnchor(pose.transform.matrix, localReferenceSpace).then(anchor => {
engine.addAnchoredNode(anchor, createBox());
}).catch(err => {
console.error('Error adding anchor', err);
});
}
clearHitTestSource();
} else {
hitTestSourceFrameNum++;
// Dispose hit test source if we don't get any hit test result
// in arbitary frame nums
if (hitTestSourceFrameNum > 2) {
clearHitTestSource();
}
}
}
engine.startFrame();
for (const view of viewerPose.views) {
engine.preRender(
session.renderState.baseLayer.getViewport(view),
view.projectionMatrix,
view.transform.matrix
);
engine.render();
}
engine.endFrame();
};
initXR();
</script>
</body>
</html>