openvr: fix for crash on exit

Before this fix, a script could call into HMD.getHUDLookAtPosition2D() while the app was shutting down, which in turn would call
getHeadPose() on the currently active display plugin.  This call could cause a crash within the openvr plugin, because the SDK was either shutdown, or in the process of shutting down on the main thread.

This fixes this by spliting the previous DisplayPlugin::getHeadPose(int) into two parts:

* updateHeadPose(int) which is only called once a frame and only by the main thread.
* getHeadPose() which is thread-safe and will return a cached copy of the hmd pose sampled by the last updateHeadPose.

interface/src/Application.cpp

@@ -1603,7 +1603,7 @@ void Application::paintGL() {
             // unmodified head pose because the only plugin that cares (the Oculus plugin) uses it
             // for rotational timewarp.  If we move to support positonal timewarp, we need to
             // ensure this contains the full pose composed with the eye offsets.
-            mat4 headPose = displayPlugin->getHeadPose(_frameCount);
+            mat4 headPose = displayPlugin->updateHeadPose(_frameCount);
 
             // FIXME we probably don't need to set the projection matrix every frame,
             // only when the display plugin changes (or in non-HMD modes when the user
@@ -2975,7 +2975,7 @@ void Application::updateMyAvatarLookAtPosition() {
             lookAtPosition.x = -lookAtPosition.x;
         }
         if (isHMD) {
-            glm::mat4 headPose = getActiveDisplayPlugin()->getHeadPose(_frameCount);
+            glm::mat4 headPose = getActiveDisplayPlugin()->getHeadPose();
             glm::quat hmdRotation = glm::quat_cast(headPose);
             lookAtSpot = _myCamera.getPosition() + myAvatar->getOrientation() * (hmdRotation * lookAtPosition);
         } else {
@@ -4927,7 +4927,7 @@ mat4 Application::getEyeOffset(int eye) const {
 
 mat4 Application::getHMDSensorPose() const {
     if (isHMDMode()) {
-        return getActiveDisplayPlugin()->getHeadPose(_frameCount);
+        return getActiveDisplayPlugin()->getHeadPose();
     }
     return mat4();
 }

interface/src/avatar/AvatarUpdate.cpp

@@ -38,7 +38,7 @@ void AvatarUpdate::synchronousProcess() {
 
     // transform the head pose from the displayPlugin into avatar coordinates.
     glm::mat4 invAvatarMat = glm::inverse(createMatFromQuatAndPos(myAvatar->getOrientation(), myAvatar->getPosition()));
-    _headPose = invAvatarMat * (myAvatar->getSensorToWorldMatrix() * qApp->getActiveDisplayPlugin()->getHeadPose(frameCount));
+    _headPose = invAvatarMat * (myAvatar->getSensorToWorldMatrix() * qApp->getActiveDisplayPlugin()->getHeadPose());
 
     if (!isThreaded()) {
         process();

interface/src/avatar/MyAvatar.cpp

@@ -1258,7 +1258,7 @@ void MyAvatar::renderBody(RenderArgs* renderArgs, ViewFrustum* renderFrustum, fl
     if (qApp->isHMDMode()) {
         glm::vec3 cameraPosition = qApp->getCamera()->getPosition();
 
-        glm::mat4 headPose = qApp->getActiveDisplayPlugin()->getHeadPose(qApp->getFrameCount());
+        glm::mat4 headPose = qApp->getActiveDisplayPlugin()->getHeadPose();
         glm::mat4 leftEyePose = qApp->getActiveDisplayPlugin()->getEyeToHeadTransform(Eye::Left);
         leftEyePose = leftEyePose * headPose;
         glm::vec3 leftEyePosition = extractTranslation(leftEyePose);

libraries/display-plugins/src/display-plugins/CompositorHelper.cpp

@@ -342,7 +342,7 @@ void CompositorHelper::computeHmdPickRay(const glm::vec2& cursorPos, glm::vec3&
 }
 
 glm::mat4 CompositorHelper::getUiTransform() const {
-    return _currentCamera * glm::inverse(_currentDisplayPlugin->getHeadPose(_currentFrame));
+    return _currentCamera * glm::inverse(_currentDisplayPlugin->getHeadPose());
 }
 
 //Finds the collision point of a world space ray

libraries/plugins/src/plugins/DisplayPlugin.h

@@ -121,8 +121,14 @@ public:
         static const glm::mat4 transform; return transform;
     }
 
-    virtual glm::mat4 getHeadPose(uint32_t frameIndex) const {
+    // will query the underlying hmd api to compute the most recent head pose
-        static const glm::mat4 pose; return pose;
+    virtual glm::mat4 updateHeadPose(uint32_t frameIndex) {
+        return glm::mat4();
+    }
+
+    // returns a copy of the most recent head pose, computed via updateHeadPose
+    virtual glm::mat4 getHeadPose() const {
+        return glm::mat4();
     }
 
     // Needed for timewarp style features

plugins/oculus/src/OculusBaseDisplayPlugin.cpp

@@ -15,14 +15,20 @@ void OculusBaseDisplayPlugin::resetSensors() {
     ovr_RecenterPose(_session);
 }
 
-glm::mat4 OculusBaseDisplayPlugin::getHeadPose(uint32_t frameIndex) const {
+glm::mat4 OculusBaseDisplayPlugin::updateHeadPose(uint32_t frameIndex) {
     static uint32_t lastFrameSeen = 0;
     auto displayTime = ovr_GetPredictedDisplayTime(_session, frameIndex);
     auto trackingState = ovr_GetTrackingState(_session, displayTime, frameIndex > lastFrameSeen);
     if (frameIndex > lastFrameSeen) {
         lastFrameSeen = frameIndex;
     }
-    return toGlm(trackingState.HeadPose.ThePose);
+    mat4 headPose = toGlm(trackingState.HeadPose.ThePose);
+    _headPoseCache.set(headPose);
+    return headPose;
+}
+
+glm::mat4 OculusBaseDisplayPlugin::getHeadPose() const {
+    return _headPoseCache.get();
 }
 
 bool OculusBaseDisplayPlugin::isSupported() const {

plugins/oculus/src/OculusBaseDisplayPlugin.h

@@ -8,6 +8,7 @@
 #pragma once
 
 #include <display-plugins/hmd/HmdDisplayPlugin.h>
+#include <ThreadSafeValueCache.h>
 
 #include <QTimer>
 
@@ -20,7 +21,8 @@ public:
 
     // Stereo specific methods
     virtual void resetSensors() override final;
-    virtual glm::mat4 getHeadPose(uint32_t frameIndex) const override;
+    virtual glm::mat4 updateHeadPose(uint32_t frameIndex) override;
+    virtual glm::mat4 getHeadPose() const override;
 
 protected:
     void customizeContext() override;
@@ -36,4 +38,5 @@ protected:
     ovrHmdDesc _hmdDesc;
     ovrLayerEyeFov _sceneLayer;
     ovrViewScaleDesc _viewScaleDesc;
+    ThreadSafeValueCache<glm::mat4> _headPoseCache { glm::mat4() };
 };

plugins/openvr/src/OpenVrDisplayPlugin.cpp

@@ -38,7 +38,7 @@ static mat4 _sensorResetMat;
 static std::array<vr::Hmd_Eye, 2> VR_EYES { { vr::Eye_Left, vr::Eye_Right } };
 
 bool OpenVrDisplayPlugin::isSupported() const {
-    return !isOculusPresent() && vr::VR_IsHmdPresent();
+    return /*!isOculusPresent() &&*/ vr::VR_IsHmdPresent();
 }
 
 void OpenVrDisplayPlugin::internalActivate() {
@@ -112,7 +112,7 @@ void OpenVrDisplayPlugin::resetSensors() {
     _sensorResetMat = glm::inverse(cancelOutRollAndPitch(m));
 }
 
-glm::mat4 OpenVrDisplayPlugin::getHeadPose(uint32_t frameIndex) const {
+glm::mat4 OpenVrDisplayPlugin::updateHeadPose(uint32_t frameIndex) {
 
     float displayFrequency = _system->GetFloatTrackedDeviceProperty(vr::k_unTrackedDeviceIndex_Hmd, vr::Prop_DisplayFrequency_Float);
     float frameDuration = 1.f / displayFrequency;
@@ -139,14 +139,21 @@ glm::mat4 OpenVrDisplayPlugin::getHeadPose(uint32_t frameIndex) const {
         _trackedDeviceLinearVelocities[i] = transformVectorFast(_sensorResetMat, toGlm(_trackedDevicePose[i].vVelocity));
         _trackedDeviceAngularVelocities[i] = transformVectorFast(_sensorResetMat, toGlm(_trackedDevicePose[i].vAngularVelocity));
     }
+
+    _headPoseCache.set(_trackedDevicePoseMat4[0]);
+
     return _trackedDevicePoseMat4[0];
 }
 
+glm::mat4 OpenVrDisplayPlugin::getHeadPose() const {
+    return _headPoseCache.get();
+}
+
 void OpenVrDisplayPlugin::hmdPresent() {
     // Flip y-axis since GL UV coords are backwards.
     static vr::VRTextureBounds_t leftBounds{ 0, 0, 0.5f, 1 };
     static vr::VRTextureBounds_t rightBounds{ 0.5f, 0, 1, 1 };
-    
+
     vr::Texture_t texture { (void*)oglplus::GetName(_compositeFramebuffer->color), vr::API_OpenGL, vr::ColorSpace_Auto };
 
     _compositor->Submit(vr::Eye_Left, &texture, &leftBounds);

plugins/openvr/src/OpenVrDisplayPlugin.h

@@ -12,6 +12,7 @@
 #include <openvr.h>
 
 #include <display-plugins/hmd/HmdDisplayPlugin.h>
+#include <ThreadSafeValueCache.h>
 
 const float TARGET_RATE_OpenVr = 90.0f;  // FIXME: get from sdk tracked device property? This number is vive-only.
 
@@ -27,7 +28,8 @@ public:
 
     // Stereo specific methods
     virtual void resetSensors() override;
-    virtual glm::mat4 getHeadPose(uint32_t frameIndex) const override;
+    virtual glm::mat4 updateHeadPose(uint32_t frameIndex) override;
+    virtual glm::mat4 getHeadPose() const override;
 
 protected:
     void internalActivate() override;
@@ -41,4 +43,5 @@ private:
     std::atomic<vr::EDeviceActivityLevel> _hmdActivityLevel { vr::k_EDeviceActivityLevel_Unknown };
     static const QString NAME;
     mutable Mutex _poseMutex;
+    ThreadSafeValueCache<glm::mat4> _headPoseCache { glm::mat4() };
 };