Merge pull request #2203 from tbirdso/xr-init-pos

feat(XR): Adjust world-to-physical factors for XR modalities

Author: floryst

Sources/Rendering/OpenGL/RenderWindow/index.js

@@ -19,6 +19,17 @@ const SCREENSHOT_PLACEHOLDER = {
   height: '100%',
 };
 
+const DEFAULT_RESET_FACTORS = {
+  vr: {
+    rescaleFactor: 1.0,
+    translateZ: -0.7, // 0.7 m forward from the camera
+  },
+  ar: {
+    rescaleFactor: 0.25, // scale down AR for viewing comfort by default
+    translateZ: -0.5, // 0.5 m forward from the camera
+  },
+};
+
 function checkRenderTargetSupport(gl, format, type) {
   // create temporary frame buffer and texture
   const framebuffer = gl.createFramebuffer();
@@ -315,6 +326,8 @@ function vtkOpenGLRenderWindow(publicAPI, model) {
         model.xrReferenceSpace = refSpace;
       });
 
+      publicAPI.resetXRScene();
+
       model.renderable.getInteractor().switchToXRAnimation();
       model.xrSceneFrame = model.xrSession.requestAnimationFrame(
         publicAPI.xrRender
@@ -324,6 +337,46 @@ function vtkOpenGLRenderWindow(publicAPI, model) {
     }
   };
 
+  publicAPI.resetXRScene = (
+    inputRescaleFactor = DEFAULT_RESET_FACTORS.vr.rescaleFactor,
+    inputTranslateZ = DEFAULT_RESET_FACTORS.vr.translateZ
+  ) => {
+    // Adjust world-to-physical parameters for different modalities
+    // Default parameter values are for VR (model.xrSessionIsAR == false)
+    let rescaleFactor = inputRescaleFactor;
+    let translateZ = inputTranslateZ;
+
+    if (
+      model.xrSessionIsAR &&
+      rescaleFactor === DEFAULT_RESET_FACTORS.vr.rescaleFactor
+    ) {
+      // Scale down by default in AR
+      rescaleFactor = DEFAULT_RESET_FACTORS.ar.rescaleFactor;
+    }
+
+    if (
+      model.xrSessionIsAR &&
+      translateZ === DEFAULT_RESET_FACTORS.vr.translateZ
+    ) {
+      // Default closer to the camera in AR
+      translateZ = DEFAULT_RESET_FACTORS.ar.translateZ;
+    }
+
+    const ren = model.renderable.getRenderers()[0];
+    ren.resetCamera();
+
+    const camera = ren.getActiveCamera();
+    let physicalScale = camera.getPhysicalScale();
+    const physicalTranslation = camera.getPhysicalTranslation();
+
+    physicalScale /= rescaleFactor;
+    translateZ *= physicalScale;
+    physicalTranslation[2] += translateZ;
+
+    camera.setPhysicalScale(physicalScale);
+    camera.setPhysicalTranslation(physicalTranslation);
+  };
+
   publicAPI.stopXR = async () => {
     if (navigator.xr === undefined) {
       // WebXR polyfill not available so nothing to do