Add support for skipping rendering frames

Add skipFramesInterval property into Q3DSViewerSettings.
This property can be used to limit the rendering framerate,
decreasing the CPU/GPU usage.

Task-number: QT3DS-4088
Change-Id: Icbf5cf208b663dbef1df6096994b94686571e357
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>

13 files changed, 121 insertions, 2 deletions

diff --git a/src/api/studio3d/q3dscommandqueue.cpp b/src/api/studio3d/q3dscommandqueue.cpp
index 300c0bf..a839e69 100644
--- a/src/api/studio3d/q3dscommandqueue.cpp
+++ b/src/api/studio3d/q3dscommandqueue.cpp
@@ -219,6 +219,8 @@ void CommandQueue::copyCommands(CommandQueue &fromQueue)
             = m_stereoEyeSeparationChanged || fromQueue.m_stereoEyeSeparationChanged;
     m_stereoProgressiveEnabledChanged
             = m_stereoProgressiveEnabledChanged || fromQueue.m_stereoProgressiveEnabledChanged;
+    m_skipFramesIntervalChanged
+            = m_skipFramesIntervalChanged || fromQueue.m_skipFramesIntervalChanged;
     m_shadeModeChanged = m_shadeModeChanged || fromQueue.m_shadeModeChanged;
     m_showRenderStatsChanged = m_showRenderStatsChanged || fromQueue.m_showRenderStatsChanged;
     m_matteColorChanged = m_matteColorChanged || fromQueue.m_matteColorChanged;
@@ -240,6 +242,8 @@ void CommandQueue::copyCommands(CommandQueue &fromQueue)
        m_stereoEyeSeparation = fromQueue.m_stereoEyeSeparation;
     if (fromQueue.m_stereoProgressiveEnabledChanged)
        m_stereoProgressiveEnabled = fromQueue.m_stereoProgressiveEnabled;
+    if (fromQueue.m_skipFramesIntervalChanged)
+       m_skipFramesInterval = fromQueue.m_skipFramesInterval;
     if (fromQueue.m_shadeModeChanged)
        m_shadeMode = fromQueue.m_shadeMode;
     if (fromQueue.m_showRenderStatsChanged)
@@ -343,6 +347,7 @@ void CommandQueue::clear(bool deleteCommandData)
     m_stereoModeChanged = false;
     m_stereoEyeSeparationChanged = false;
     m_stereoProgressiveEnabledChanged = false;
+    m_skipFramesIntervalChanged = false;
     m_shadeModeChanged = false;
     m_showRenderStatsChanged = false;
     m_matteColorChanged = false;
diff --git a/src/api/studio3d/q3dscommandqueue_p.h b/src/api/studio3d/q3dscommandqueue_p.h
index 6096439..9939cb0 100644
--- a/src/api/studio3d/q3dscommandqueue_p.h
+++ b/src/api/studio3d/q3dscommandqueue_p.h
@@ -144,6 +144,7 @@ public:
     bool m_stereoModeChanged = false;
     bool m_stereoEyeSeparationChanged = false;
     bool m_stereoProgressiveEnabledChanged = false;
+    bool m_skipFramesIntervalChanged = false;
     bool m_shadeModeChanged = false;
     bool m_showRenderStatsChanged = false;
     bool m_matteColorChanged = false;
@@ -159,6 +160,7 @@ public:
     Q3DSViewerSettings::StereoMode m_stereoMode = Q3DSViewerSettings::StereoModeMono;
     double m_stereoEyeSeparation = 0.4;
     bool m_stereoProgressiveEnabled = false;
+    int m_skipFramesInterval = 0;
     Q3DSViewerSettings::ShadeMode m_shadeMode = Q3DSViewerSettings::ShadeModeShaded;
     bool m_showRenderStats = false;
     QColor m_matteColor = QColor(Qt::black);
diff --git a/src/api/studio3d/q3dsviewersettings.cpp b/src/api/studio3d/q3dsviewersettings.cpp
index 9025bb8..cbb273a 100644
--- a/src/api/studio3d/q3dsviewersettings.cpp
+++ b/src/api/studio3d/q3dsviewersettings.cpp
@@ -371,6 +371,44 @@ void Q3DSViewerSettings::setStereoProgressiveEnabled(bool enabled)
 }
 
 /*!
+    \qmlproperty int ViewerSettings::skipFramesInterval
+
+    \since QtStudio3D.OpenGL 2.7
+
+    Sets interval for skipping frame rendering. The default value is 0
+    meaning all frames are rendered. Setting this to 1 renders every
+    other frame (30fps on 60Hz screen), 2 every third frame (20fps on
+    60Hz screen) etc. This property allows slowing down 3D rendering
+    while keeping QtQuick UI rendering intact, decreasing the CPU/GPU
+    usage.
+ */
+/*!
+    \property Q3DSViewerSettings::skipFramesInterval
+
+    \since Qt 3D Studio 2.7
+
+    Sets interval for skipping frame rendering. The default value is 0
+    meaning all frames are rendered. Setting this to 1 renders every
+    other frame (30fps on 60Hz screen), 2 every third frame (20fps on
+    60Hz screen) etc. This property allows slowing down 3D rendering
+    while keeping QtQuick UI rendering intact, decreasing the CPU/GPU
+    usage.
+ */
+
+int Q3DSViewerSettings::skipFramesInterval() const
+{
+    return d_ptr->m_skipFramesInterval;
+}
+
+void Q3DSViewerSettings::setSkipFramesInterval(int interval)
+{
+    if (d_ptr->m_skipFramesInterval != interval) {
+        d_ptr->setSkipFramesInterval(interval);
+        Q_EMIT skipFramesIntervalChanged(interval);
+    }
+}
+
+/*!
     \qmlproperty bool ViewerSettings::matteEnabled
 
     Specifies if the empty area around the presentation (applicable when
@@ -450,6 +488,7 @@ Q3DSViewerSettingsPrivate::Q3DSViewerSettingsPrivate(Q3DSViewerSettings *q)
     , m_stereoMode(Q3DSViewerSettings::StereoModeMono)
     , m_stereoEyeSeparation(0.4)
     , m_stereoProgressiveEnabled(false)
+    , m_skipFramesInterval(0)
     , m_savedSettings(nullptr)
 {
 }
@@ -470,6 +509,7 @@ void Q3DSViewerSettingsPrivate::setViewerApp(Q3DSViewer::Q3DSViewerApp *app)
         setStereoMode(m_stereoMode);
         setStereoEyeSeparation(m_stereoEyeSeparation);
         setStereoProgressiveEnabled(m_stereoProgressiveEnabled);
+        setSkipFramesInterval(m_skipFramesInterval);
     }
 }
 
@@ -485,6 +525,7 @@ void Q3DSViewerSettingsPrivate::setCommandQueue(CommandQueue *queue)
         setStereoMode(m_stereoMode);
         setStereoEyeSeparation(m_stereoEyeSeparation);
         setStereoProgressiveEnabled(m_stereoProgressiveEnabled);
+        setSkipFramesInterval(m_skipFramesInterval);
     }
 }
 
@@ -519,6 +560,8 @@ void Q3DSViewerSettingsPrivate::load(const QString &group, const QString &organi
                 m_savedSettings->value(QStringLiteral("stereoEyeSeparation")).toDouble());
     q_ptr->setStereoProgressiveEnabled(
                 m_savedSettings->value(QStringLiteral("stereoProgressiveEnabled")).toBool());
+    q_ptr->setSkipFramesInterval(
+                m_savedSettings->value(QStringLiteral("skipFramesInterval")).toInt());
     q_ptr->setMatteEnabled(m_savedSettings->value(QStringLiteral("matteEnabled")).toBool());
 }
 
@@ -627,6 +670,17 @@ void Q3DSViewerSettingsPrivate::setStereoProgressiveEnabled(bool enabled)
     }
 }
 
+void Q3DSViewerSettingsPrivate::setSkipFramesInterval(int interval)
+{
+    m_skipFramesInterval = interval;
+    if (m_viewerApp) {
+        m_viewerApp->SetSkipFramesInterval(interval);
+    } else if (m_commandQueue) {
+        m_commandQueue->m_skipFramesInterval = interval;
+        m_commandQueue->m_skipFramesIntervalChanged = true;
+    }
+}
+
 void Q3DSViewerSettingsPrivate::initSettingsStore(const QString &group, const QString &organization,
                                                   const QString &application)
 {
diff --git a/src/api/studio3d/q3dsviewersettings.h b/src/api/studio3d/q3dsviewersettings.h
index f956649..80b36df 100644
--- a/src/api/studio3d/q3dsviewersettings.h
+++ b/src/api/studio3d/q3dsviewersettings.h
@@ -53,6 +53,7 @@ class Q_STUDIO3D_EXPORT Q3DSViewerSettings : public QObject
     Q_PROPERTY(StereoMode stereoMode READ stereoMode WRITE setStereoMode NOTIFY stereoModeChanged REVISION 1)
     Q_PROPERTY(double stereoEyeSeparation READ stereoEyeSeparation WRITE setStereoEyeSeparation NOTIFY stereoEyeSeparationChanged REVISION 1)
     Q_PROPERTY(bool stereoProgressiveEnabled READ stereoProgressiveEnabled WRITE setStereoProgressiveEnabled NOTIFY stereoProgressiveEnabledChanged REVISION 2)
+    Q_PROPERTY(int skipFramesInterval READ skipFramesInterval WRITE setSkipFramesInterval NOTIFY skipFramesIntervalChanged REVISION 2)
 
 public:
     enum ShadeMode {
@@ -84,6 +85,7 @@ public:
     StereoMode stereoMode() const;
     double stereoEyeSeparation() const;
     Q_REVISION(2) bool stereoProgressiveEnabled() const;
+    Q_REVISION(2) int skipFramesInterval() const;
 
     Q_INVOKABLE void save(const QString &group, const QString &organization = QString(),
                           const QString &application = QString());
@@ -98,6 +100,7 @@ public Q_SLOTS:
     void setStereoMode(StereoMode mode);
     void setStereoEyeSeparation(double separation);
     Q_REVISION(2) void setStereoProgressiveEnabled(bool enabled);
+    Q_REVISION(2) void setSkipFramesInterval(int interval);
 
 Q_SIGNALS:
     void matteEnabledChanged(bool enabled);
@@ -108,6 +111,7 @@ Q_SIGNALS:
     void stereoModeChanged(StereoMode mode);
     void stereoEyeSeparationChanged(double separation);
     Q_REVISION(2) void stereoProgressiveEnabledChanged(bool enabled);
+    Q_REVISION(2) void skipFramesIntervalChanged(int interval);
 
 private:
     Q_DISABLE_COPY(Q3DSViewerSettings)
diff --git a/src/api/studio3d/q3dsviewersettings_p.h b/src/api/studio3d/q3dsviewersettings_p.h
index 44e1227..6a2dc75 100644
--- a/src/api/studio3d/q3dsviewersettings_p.h
+++ b/src/api/studio3d/q3dsviewersettings_p.h
@@ -70,6 +70,7 @@ public:
     void setStereoMode(Q3DSViewerSettings::StereoMode mode);
     void setStereoEyeSeparation(double separation);
     void setStereoProgressiveEnabled(bool enabled);
+    void setSkipFramesInterval(int interval);
 
 public:
     Q3DSViewerSettings *q_ptr;
@@ -88,6 +89,7 @@ private:
     Q3DSViewerSettings::StereoMode m_stereoMode;
     double m_stereoEyeSeparation;
     bool m_stereoProgressiveEnabled;
+    int m_skipFramesInterval;
     QSettings *m_savedSettings;
 };
 
diff --git a/src/api/studio3dqml/q3dsrenderer.cpp b/src/api/studio3dqml/q3dsrenderer.cpp
index f7bd25b..8f0081e 100644
--- a/src/api/studio3dqml/q3dsrenderer.cpp
+++ b/src/api/studio3dqml/q3dsrenderer.cpp
@@ -353,6 +353,8 @@ void Q3DSRenderer::processCommands()
         m_settings->setStereoEyeSeparation(m_commands.m_stereoEyeSeparation);
     if (m_commands.m_stereoProgressiveEnabledChanged)
         m_settings->setStereoProgressiveEnabled(m_commands.m_stereoProgressiveEnabled);
+    if (m_commands.m_skipFramesIntervalChanged)
+        m_settings->setSkipFramesInterval(m_commands.m_skipFramesInterval);
     if (m_commands.m_shadeModeChanged)
         m_settings->setShadeMode(m_commands.m_shadeMode);
     if (m_commands.m_matteColorChanged)
diff --git a/src/engine/Qt3DSRenderRuntimeBindingImplRenderer.cpp b/src/engine/Qt3DSRenderRuntimeBindingImplRenderer.cpp
index 9fda560..78a1d17 100644
--- a/src/engine/Qt3DSRenderRuntimeBindingImplRenderer.cpp
+++ b/src/engine/Qt3DSRenderRuntimeBindingImplRenderer.cpp
@@ -172,6 +172,12 @@ struct SRenderer : public Q3DStudio::ITegraApplicationRenderEngine
         return false;
     }
 
+    void SetSkipFramesInterval(int interval) override
+    {
+        if (m_BindingCore && m_BindingCore->m_Context)
+            m_BindingCore->m_Context->SetSkipFramesInterval(interval);
+    }
+
     void SetShadeMode(Q3DStudio::TegraRenderShadeModes::Enum inShade) override
     {
         if (m_BindingCore && m_BindingCore->m_Context) {
diff --git a/src/engine/Qt3DSRuntimeView.h b/src/engine/Qt3DSRuntimeView.h
index 8690b99..cb6da7f 100644
--- a/src/engine/Qt3DSRuntimeView.h
+++ b/src/engine/Qt3DSRuntimeView.h
@@ -149,6 +149,7 @@ public:
     virtual double GetStereoEyeSeparation() const = 0;
     virtual void SetStereoProgressiveEnabled(bool enabled) = 0;
     virtual bool GetStereoProgressiveEnabled() const = 0;
+    virtual void SetSkipFramesInterval(int interval) = 0;
 
     // TODO: To be removed, not used anywhere anymore
     void CycleScaleMode()
diff --git a/src/runtime/Qt3DSApplication.cpp b/src/runtime/Qt3DSApplication.cpp
index f7f8b46..f12fef9 100644
--- a/src/runtime/Qt3DSApplication.cpp
+++ b/src/runtime/Qt3DSApplication.cpp
@@ -658,7 +658,7 @@ struct SApp : public IApplication
     DataOutputMap m_dataOutputDefs;
 
     bool m_initialFrame = true;
-
+    int m_skipFrameCount = 0;
     SSlideResourceCounter m_resourceCounter;
     QSet<QString> m_createSet;
 
@@ -1119,6 +1119,23 @@ struct SApp : public IApplication
 
     void ResetDirtyCounter() { m_DirtyCountdown = 5; }
 
+    // Returns true when skipping the frame, false when rendering it
+    bool checkSkipFrame()
+    {
+        auto &rc = m_RuntimeFactory->GetQt3DSRenderContext();
+        int skipFrames = rc.GetSkipFramesInterval();
+        if (skipFrames == 0)
+            return false;
+
+        if (m_skipFrameCount <= 0) {
+            m_skipFrameCount = skipFrames;
+            return false;
+        }
+
+        m_skipFrameCount--;
+        return true;
+    }
+
     // Update all the presentations and render them.
     bool UpdateAndRender() override
     {
@@ -1165,7 +1182,12 @@ struct SApp : public IApplication
         bool renderNextFrame = false;
         if (m_LastRenderWasDirty || dirty || m_initialFrame)
             renderNextFrame = true;
-        Render();
+
+        bool skip = checkSkipFrame();
+        // If we skip rendering this frame, mark next frame to be rendered
+        renderNextFrame |= skip;
+        if (!skip)
+            Render();
 
         m_InputEnginePtr->ClearInputFrame();
 
diff --git a/src/runtimerender/Qt3DSRenderContextCore.cpp b/src/runtimerender/Qt3DSRenderContextCore.cpp
index dde70fd..d1d0fff 100644
--- a/src/runtimerender/Qt3DSRenderContextCore.cpp
+++ b/src/runtimerender/Qt3DSRenderContextCore.cpp
@@ -249,6 +249,7 @@ struct SRenderContext : public IQt3DSRenderContext
     StereoViews::Enum m_StereoView;
     double m_StereoEyeSeparation;
     bool m_StereoProgressiveEnabled;
+    int m_SkipFramesInterval;
     bool m_WireframeMode;
     bool m_subPresentationRenderInLayer;
     Option<QT3DSVec4> m_SceneColor;
@@ -291,6 +292,7 @@ struct SRenderContext : public IQt3DSRenderContext
         , m_StereoView(StereoViews::Mono)
         , m_StereoEyeSeparation(0.4)
         , m_StereoProgressiveEnabled(false)
+        , m_SkipFramesInterval(0)
         , m_WireframeMode(false)
         , m_subPresentationRenderInLayer(false)
         , m_matteEnabled(false)
@@ -486,6 +488,15 @@ struct SRenderContext : public IQt3DSRenderContext
                                               || m_StereoMode == StereoModes::TopBottom);
     }
 
+    void SetSkipFramesInterval(int interval) override
+    {
+        m_SkipFramesInterval = interval;
+    }
+
+    int GetSkipFramesInterval() const override {
+        return m_SkipFramesInterval;
+    }
+
     void SetWireframeMode(bool inEnable) override { m_WireframeMode = inEnable; }
 
     bool GetWireframeMode() override { return m_WireframeMode; }
diff --git a/src/runtimerender/Qt3DSRenderContextCore.h b/src/runtimerender/Qt3DSRenderContextCore.h
index 8382fc6..64e91c0 100644
--- a/src/runtimerender/Qt3DSRenderContextCore.h
+++ b/src/runtimerender/Qt3DSRenderContextCore.h
@@ -205,6 +205,8 @@ namespace render {
         virtual double GetStereoEyeSeparation() const = 0;
         virtual void SetStereoProgressiveEnabled(bool enabled) = 0;
         virtual bool GetStereoProgressiveEnabled() const = 0;
+        virtual void SetSkipFramesInterval(int interval) = 0;
+        virtual int GetSkipFramesInterval() const = 0;
 
         virtual void SetWireframeMode(bool inEnable) = 0;
         virtual bool GetWireframeMode() = 0;
diff --git a/src/viewer/Qt3DSViewerApp.cpp b/src/viewer/Qt3DSViewerApp.cpp
index 5d8393a..7d94f3a 100644
--- a/src/viewer/Qt3DSViewerApp.cpp
+++ b/src/viewer/Qt3DSViewerApp.cpp
@@ -886,6 +886,12 @@ bool Q3DSViewerApp::GetStereoProgressiveEnabled() const
     return 0;
 }
 
+void Q3DSViewerApp::SetSkipFramesInterval(int interval)
+{
+    if (m_Impl.m_view && m_Impl.m_view->GetTegraRenderEngine())
+        m_Impl.m_view->GetTegraRenderEngine()->SetSkipFramesInterval(interval);
+}
+
 void Q3DSViewerApp::setMatteColor(const QColor &color)
 {
     if (m_Impl.m_view && m_Impl.m_view->GetTegraRenderEngine()) {
diff --git a/src/viewer/Qt3DSViewerApp.h b/src/viewer/Qt3DSViewerApp.h
index ab723cd..8aca9e1 100644
--- a/src/viewer/Qt3DSViewerApp.h
+++ b/src/viewer/Qt3DSViewerApp.h
@@ -328,6 +328,8 @@ public:
     void SetStereoProgressiveEnabled(bool enabled);
     bool GetStereoProgressiveEnabled() const;
 
+    void SetSkipFramesInterval(int interval);
+
     void setMatteColor(const QColor &color);
     void setShowOnScreenStats(bool s);