feat(WebXR): Add initial support for WebXR viewing with VTK.js

Adds initial support for viewing VolView scene in WebXR on the local
device. Note that performance may vary widely across devices.

src/components/RenderingModule.vue

@@ -4,10 +4,11 @@ import { useCurrentImage } from '../composables/useCurrentImage';
 import VolumeProperties from './VolumeProperties.vue';
 import VolumeRendering from './VolumeRendering.vue';
 import VolumePresets from './VolumePresets.vue';
+import WebXRRendering from './WebXRRendering.vue';
 import LayerList from './LayerList.vue';
 
 export default defineComponent({
-  components: { VolumeRendering, VolumePresets, VolumeProperties, LayerList },
+  components: { VolumeRendering, VolumePresets, VolumeProperties, WebXRRendering, LayerList },
   setup() {
     const { currentImageData } = useCurrentImage();
     const hasCurrentImage = computed(() => !!currentImageData.value);
@@ -31,6 +32,7 @@ export default defineComponent({
     <template v-if="hasCurrentImage">
       <volume-rendering />
       <v-expansion-panels v-model="panels" multiple variant="accordion">
+
         <v-expansion-panel value="preset">
           <v-expansion-panel-title>
             <v-icon class="flex-grow-0 mr-4">mdi-palette</v-icon>
@@ -60,6 +62,17 @@ export default defineComponent({
             <layer-list />
           </v-expansion-panel-text>
         </v-expansion-panel>
+
+        <v-expansion-panel value="webxr">
+          <v-expansion-panel-title>
+            <v-icon class="flex-grow-0 mr-4">mdi-palette</v-icon>
+            WebXR Rendering
+          </v-expansion-panel-title>
+          <v-expansion-panel-text>
+            <web-x-r-rendering />
+          </v-expansion-panel-text>
+        </v-expansion-panel>
+
       </v-expansion-panels>
     </template>
     <template v-else>

src/components/WebXRRendering.vue

@@ -0,0 +1,109 @@
+<script setup lang="ts">
+import {
+  ref,
+} from 'vue';
+
+import { XrSessionTypes } from '@kitware/vtk.js/Rendering/WebXR/RenderWindowHelper/Constants.js';
+import { onVTKEvent } from '@/src/composables/onVTKEvent';
+import { useViewProxy } from '../composables/useViewProxy';
+import useVTKWebXRStore from '../store/view-configs/webxr';
+import { ViewProxyType } from '../core/proxies';
+import { InitViewIDs } from '../config';
+
+const TARGET_VIEW_ID = InitViewIDs.Three;
+const vtkWebXRStore = useVTKWebXRStore();
+
+const xrSessionRunning = ref(vtkWebXRStore.isXrSessionRunning());
+    
+const namedXrSessionTypes = [
+  { value: 0, title: 'VR Headset'},
+  { value: 1, title: 'AR Mobile Device'},
+  { value: 2, title: 'Holographic Display'},
+  { value: 3, title: 'AR Headset'},
+];
+
+function updateXRStateFunc() {
+  xrSessionRunning.value = !!vtkWebXRStore.xrHelper.getXrSession();
+};
+
+function startXRFunc(sessionType:XrSessionTypes) {
+  const { viewProxy } = useViewProxy(TARGET_VIEW_ID, ViewProxyType.Volume);
+  vtkWebXRStore.xrHelper.setRenderWindow(viewProxy.value.getOpenGLRenderWindow());
+  vtkWebXRStore.xrHelper.startXR(sessionType);
+}
+
+onVTKEvent(vtkWebXRStore.xrHelper, 'onModified', updateXRStateFunc);
+
+function onSendToXRClick() {
+  if(vtkWebXRStore.xrHelper.getXrSession() !== null) {
+    throw new Error('Cannot send to XR: session already running');
+  }
+  if(vtkWebXRStore.selectedXrSessionType === null) {
+    throw new Error('Cannot send to XR: no session type selected');
+  }
+
+  const xrSessionType = vtkWebXRStore.selectedXrSessionType ? vtkWebXRStore.selectedXrSessionType.value : 0;
+
+  if(xrSessionType === XrSessionTypes.LookingGlassVR) {
+    // The Looking Glass WebXR Polyfill overrides support for other XR sessions.
+    vtkWebXRStore.isXrSessionTypeLocked = true;
+
+    // Import the Looking Glass WebXR Polyfill override.
+    // Assumes that the Looking Glass Bridge native application is already running.
+    // See https://docs.lookingglassfactory.com/developer-tools/webxr
+    import(
+      // @ts-expect-error TS2307
+      // eslint-disable-next-line import/no-unresolved, import/extensions
+      /* webpackIgnore: true */ 'https://unpkg.com/@lookingglass/[email protected]/dist/bundle/webxr.js'
+    ).then((obj) => {
+      // eslint-disable-next-line no-new
+      new obj.LookingGlassWebXRPolyfill();
+
+      // There is a delay between when the Looking Glass polyfill starts and when
+      // the Looking Glass Bridge application finishes populating device information.
+      // Attempting to start the XR session in the intermediate period can result in
+      // undefined behavior such as a failure to start the session or an attempt to start
+      // a standard VR HMD session.
+      // A timeout of 1 second is used to account for this delay as a workaround.
+      // In the future we may explore handling an event notification from the Looking Glass polyfill
+      // when a new Looking Glass device is ready for WebXR rendering.
+      setTimeout(() => startXRFunc(xrSessionType), 1000);
+    });
+  } else if((navigator as any).xr === undefined) {
+    import(
+    // @ts-expect-error TS2307
+    // eslint-disable-next-line import/no-unresolved, import/extensions
+    /* webpackIgnore: true */ 'https://cdn.jsdelivr.net/npm/webxr-polyfill@latest/build/webxr-polyfill.js'
+    ).then(() => {
+      startXRFunc(xrSessionType);
+    })
+  } else {
+    startXRFunc(xrSessionType);
+  }
+};
+
+function onReturnFromXRClick() {
+  if(vtkWebXRStore.xrHelper.getXrSession() === null) {
+    throw new Error('Cannot return from XR: no session running');
+  }
+  vtkWebXRStore.xrHelper.stopXR();
+};
+
+</script>
+
+<template>
+  <div class="mx-2">
+    <v-combobox
+    v-model="vtkWebXRStore.selectedXrSessionType"
+    :items="namedXrSessionTypes"
+    label="Mixed Reality Session Type"
+    item-text="title"
+    item-value="value"
+    :disabled="vtkWebXRStore.isXrSessionTypeLocked"
+    />
+    <button v-if="!xrSessionRunning && vtkWebXRStore.selectedXrSessionType" @click="onSendToXRClick">
+      Send to {{ vtkWebXRStore.selectedXrSessionType.title }}
+    </button>
+    <button v-if="xrSessionRunning" @click="onReturnFromXRClick">Return from XR</button>
+  </div>
+</template>

src/store/view-configs/webxr.ts

@@ -0,0 +1,22 @@
+import { defineStore } from 'pinia';
+import { ref, Ref } from 'vue';
+import vtkWebXRRenderWindowHelper from '@kitware/vtk.js/Rendering/WebXR/RenderWindowHelper';
+
+export const useVTKWebXRStore = defineStore('vtkWebXR', () => {
+    const xrHelper = vtkWebXRRenderWindowHelper.newInstance();
+    const selectedXrSessionType : Ref<{title: string, value: number} | null> = ref(null);
+    const isXrSessionTypeLocked = ref(false);
+
+    function isXrSessionRunning() : Boolean {
+        return !!xrHelper.getXrSession();
+    }
+
+  return {
+    xrHelper,
+    selectedXrSessionType,
+    isXrSessionTypeLocked,
+    isXrSessionRunning
+  };
+});
+
+export default useVTKWebXRStore;