First pass at interpolation fix during playback with screenshots

include/openspace/interaction/sessionrecording.h

@@ -30,6 +30,7 @@
 #include <openspace/properties/scalar/boolproperty.h>
 #include <openspace/scripting/lualibrary.h>
 #include <vector>
+#include <chrono>
 
 namespace openspace::interaction {
 
@@ -117,6 +118,20 @@ public:
      */
     double fixedDeltaTimeDuringFrameOutput() const;
 
+    /**
+     * Returns the number of microseconds that have elapsed since playback started, if
+     * playback is set to be in the mode where a screenshot is captured with every
+     * rendered frame (enableTakeScreenShotDuringPlayback() is used to enable this mode).
+     * At the start of playback, this timer is set to the current steady_clock value.
+     * However, during playback it is incremented by the fixed framerate of the playback
+     * rather than the actual clock value (as in normal operation).
+     *
+     * \returns number of microseconds elapsed since playback started in terms of the
+     *          number of rendered frames multiplied by the fixed time increment per
+     *          frame
+     */
+    std::chrono::steady_clock::time_point currentPlaybackInterpolationTime() const;
+
     /**
      * Starts a recording session, which will save data to the provided filename
      * according to the data format specified, and will continue until recording is
@@ -627,6 +642,9 @@ protected:
     bool _saveRenderingDuringPlayback = false;
     double _saveRenderingDeltaTime = 1.0 / 30.0;
     double _saveRenderingCurrentRecordedTime;
+    std::chrono::steady_clock::duration _saveRenderingDeltaTime_interpolation_usec;
+    std::chrono::steady_clock::time_point _saveRenderingCurrentRecordedTime_interpolation;
+    long long _saveRenderingClockInterpolation_countsPerSec;
 
     unsigned char _keyframeBuffer[_saveBufferMaxSize_bytes];
 

src/interaction/sessionrecording.cpp

@@ -324,11 +324,15 @@ bool SessionRecording::startPlayback(std::string& filename,
         return false;
     }
     //Set time reference mode
+    using namespace std::chrono;
     double now = global::windowDelegate->applicationTime();
     _timestampPlaybackStarted_application = now;
     _timestampPlaybackStarted_simulation = global::timeManager->time().j2000Seconds();
     _timestampApplicationStarted_simulation = _timestampPlaybackStarted_simulation - now;
     _playbackTimeReferenceMode = timeMode;
+    _saveRenderingCurrentRecordedTime_interpolation = steady_clock::now();
+    _saveRenderingClockInterpolation_countsPerSec =
+        system_clock::duration::period::den / system_clock::duration::period::num;
 
     //Set playback flags to true for all modes
     _playbackActive_camera = true;
@@ -407,6 +411,8 @@ void SessionRecording::signalPlaybackFinishedForComponent(RecordedType type) {
 void SessionRecording::enableTakeScreenShotDuringPlayback(int fps) {
     _saveRenderingDuringPlayback = true;
     _saveRenderingDeltaTime = 1.0 / fps;
+    _saveRenderingDeltaTime_interpolation_usec =
+        std::chrono::microseconds(static_cast<long>(_saveRenderingDeltaTime * 1000000));
 }
 
 void SessionRecording::disableTakeScreenShotDuringPlayback() {
@@ -907,6 +913,10 @@ double SessionRecording::fixedDeltaTimeDuringFrameOutput() const {
     }
 }
 
+std::chrono::steady_clock::time_point SessionRecording::currentPlaybackInterpolationTime() const {
+    return _saveRenderingCurrentRecordedTime_interpolation;
+}
+
 bool SessionRecording::playbackCamera() {
     Timestamps times;
     datamessagestructures::CameraKeyframe kf;
@@ -1388,6 +1398,8 @@ bool SessionRecording::addKeyframeToTimeline(RecordedType type,
 }
 
 void SessionRecording::moveAheadInTime() {
+    using namespace std::chrono;
+
     double currTime = currentTime();
     lookForNonCameraKeyframesThatHaveComeDue(currTime);
     updateCameraWithOrWithoutNewKeyframes(currTime);
@@ -1398,6 +1410,8 @@ void SessionRecording::moveAheadInTime() {
             global::navigationHandler->orbitalNavigator().anchorNode();
         const Renderable* focusRenderable = focusNode->renderable();
         if (!focusRenderable || focusRenderable->renderedWithDesiredData()) {
+            _saveRenderingCurrentRecordedTime_interpolation +=
+                _saveRenderingDeltaTime_interpolation_usec;
             _saveRenderingCurrentRecordedTime += _saveRenderingDeltaTime;
             global::renderEngine->takeScreenshot();
         }

src/scene/scene.cpp

@@ -27,6 +27,7 @@
 #include <openspace/engine/globals.h>
 #include <openspace/engine/globalscallbacks.h>
 #include <openspace/engine/windowdelegate.h>
+#include <openspace/interaction/sessionrecording.h>
 #include <openspace/query/query.h>
 #include <openspace/rendering/renderengine.h>
 #include <openspace/scene/scenegraphnode.h>
@@ -494,9 +495,14 @@ void Scene::addPropertyInterpolation(properties::Property* prop, float durationS
         ghoul::easingFunction<float>(easingFunction);
 
     // First check if the current property already has an interpolation information
+    std::chrono::steady_clock::time_point now = (
+        global::sessionRecording->isSavingFramesDuringPlayback()     ?
+        global::sessionRecording->currentPlaybackInterpolationTime() :
+        std::chrono::steady_clock::now()
+    );
     for (PropertyInterpolationInfo& info : _propertyInterpolationInfos) {
         if (info.prop == prop) {
-            info.beginTime = std::chrono::steady_clock::now();
+            info.beginTime = now;
             info.durationSeconds = durationSeconds;
             info.easingFunction = func;
             // If we found it, we can break since we make sure that each property is only
@@ -543,8 +549,13 @@ void Scene::updateInterpolations() {
 
     using namespace std::chrono;
 
-    auto now = steady_clock::now();
-
+    steady_clock::time_point now;
+    if (global::sessionRecording->isSavingFramesDuringPlayback()) {
+        now = global::sessionRecording->currentPlaybackInterpolationTime();
+    }
+    else {
+        now = steady_clock::now();
+    }
     // First, let's update the properties
     for (PropertyInterpolationInfo& i : _propertyInterpolationInfos) {
         long long usPassed = duration_cast<std::chrono::microseconds>(