Don't render when scene is not changing

Reduce CPU and GPU load by checking if the scene has changed and render
only if it has.

Task-number: QT3DS-4042
Change-Id: I54e447760f04fdad8d64319f326245175b471331
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>

14 files changed, 51 insertions, 32 deletions

diff --git a/src/api/studio3dqml/q3dsrenderer.cpp b/src/api/studio3dqml/q3dsrenderer.cpp
index 7d63b30..c902934 100644
--- a/src/api/studio3dqml/q3dsrenderer.cpp
+++ b/src/api/studio3dqml/q3dsrenderer.cpp
@@ -197,27 +197,32 @@ void Q3DSRenderer::render()
     // Don't render if the plugin is hidden; however, if hidden, but sure
     // to process pending commands so we can be shown again.
     if (m_initialized) {
+        bool updateAgain = false;
         if (m_visibleFlag)
-            draw();
+            updateAgain = draw();
         else
             processCommands();
-        update(); // mark as dirty to ensure update again
+
+        if (updateAgain)
+            update(); // mark as dirty to ensure update again
     }
 }
 
 /** Cause Qt3DS runtime to render content.
  *  Initializes GL and the runtime when called the first time.
  */
-void Q3DSRenderer::draw()
+bool Q3DSRenderer::draw()
 {
+    bool ret = true;
     if (m_runtime && m_runtime->IsInitialised() && m_window) {
         if (m_initialized)
             m_runtime->RestoreState();
-        m_runtime->Render();
+        ret = m_runtime->Render();
         m_runtime->SaveState();
 
         m_window->resetOpenGLState();
     }
+    return ret;
 }
 
 bool Q3DSRenderer::initializeRuntime(QOpenGLFramebufferObject *inFbo)
diff --git a/src/api/studio3dqml/q3dsrenderer_p.h b/src/api/studio3dqml/q3dsrenderer_p.h
index 0817494..dbc85a2 100644
--- a/src/api/studio3dqml/q3dsrenderer_p.h
+++ b/src/api/studio3dqml/q3dsrenderer_p.h
@@ -89,7 +89,7 @@ protected:
     static void onInitHandler(void *userData);
     static void onUpdateHandler(void *userData);
     bool initializeRuntime(QOpenGLFramebufferObject *inFbo);
-    void draw();
+    bool draw();
     void render() override;
     void synchronize(QQuickFramebufferObject *inView) override;
     void releaseRuntime();
diff --git a/src/engine/Qt3DSRenderRuntimeBinding.cpp b/src/engine/Qt3DSRenderRuntimeBinding.cpp
index 28c5403..e830e0f 100644
--- a/src/engine/Qt3DSRenderRuntimeBinding.cpp
+++ b/src/engine/Qt3DSRenderRuntimeBinding.cpp
@@ -1505,9 +1505,11 @@ struct Qt3DSRenderSceneManager : public Q3DStudio::ISceneManager,
                                        bool firstFrame) override
     {
         Qt3DSRenderScene *theFirstScene = nullptr;
-        for (QT3DSU32 idx = 0, end = m_Scenes.size(); idx < end && theFirstScene == nullptr; ++idx)
+        for (QT3DSU32 idx = 0, end = m_Scenes.size(); idx < end; ++idx) {
             if (m_Scenes[idx].second->m_RuntimePresentation == inPresentation)
                 theFirstScene = m_Scenes[idx].second;
+            m_Scenes[idx].second->TransferDirtyProperties();
+        }
 
         if (theFirstScene && theFirstScene->m_Presentation) {
             m_LastRenderedScene = theFirstScene;
diff --git a/src/engine/Qt3DSRuntimeView.cpp b/src/engine/Qt3DSRuntimeView.cpp
index fd3be65..2335cf1 100644
--- a/src/engine/Qt3DSRuntimeView.cpp
+++ b/src/engine/Qt3DSRuntimeView.cpp
@@ -179,7 +179,7 @@ public:
     void Cleanup() override;
 
     bool CanRender() override;
-    void Render() override;
+    bool Render() override;
     bool WasLastFrameDirty() override;
 
     bool HandleMessage(const QEvent *inEvent) override;
@@ -394,8 +394,9 @@ bool CRuntimeView::CanRender()
  *  returns KD_TRUE to call egl_render and swap properly, KD_FALSE if there has been no scene update
  *or redraw.
  */
-void CRuntimeView::Render()
+bool CRuntimeView::Render()
 {
+    bool ret = true;
     if (m_Application.mPtr == nullptr) {
         // InitializeGraphics has not been called
         QT3DS_ASSERT(false);
@@ -403,7 +404,7 @@ void CRuntimeView::Render()
 
     PerfLogGeneralEvent1(DATALOGGER_FRAME);
 
-    m_Application->UpdateAndRender();
+    ret = m_Application->UpdateAndRender();
 
     if (m_startupTime < 0 && m_startupTimer && m_startupTimer->isValid()) {
 
@@ -457,6 +458,7 @@ void CRuntimeView::Render()
 
         manager.PopState();
     }
+    return ret;
 }
 
 bool CRuntimeView::WasLastFrameDirty()
diff --git a/src/engine/Qt3DSRuntimeView.h b/src/engine/Qt3DSRuntimeView.h
index e3f57d1..e0061b0 100644
--- a/src/engine/Qt3DSRuntimeView.h
+++ b/src/engine/Qt3DSRuntimeView.h
@@ -185,7 +185,7 @@ public: // loading
 
     virtual bool CanRender() = 0;
 
-    virtual void Render() = 0;
+    virtual bool Render() = 0;
 
     virtual bool WasLastFrameDirty() = 0;
 
diff --git a/src/runtime/Qt3DSApplication.cpp b/src/runtime/Qt3DSApplication.cpp
index cb8f732..79866c5 100644
--- a/src/runtime/Qt3DSApplication.cpp
+++ b/src/runtime/Qt3DSApplication.cpp
@@ -1031,7 +1031,7 @@ struct SApp : public IApplication
         } // End QT3DS_PERF_SCOPED_TIMER scope
     }
 
-    void UpdateScenes() { m_RuntimeFactory->GetSceneManager().Update(); }
+    bool UpdateScenes() { return m_RuntimeFactory->GetSceneManager().Update(); }
 
     bool LazyLoadSubPresentations()
     {
@@ -1113,7 +1113,7 @@ struct SApp : public IApplication
     void ResetDirtyCounter() { m_DirtyCountdown = 5; }
 
     // Update all the presentations and render them.
-    void UpdateAndRender() override
+    bool UpdateAndRender() override
     {
         QT3DS_ASSERT(m_AppLoadContext.mPtr == NULL);
         m_ThisFrameStartTime = qt3ds::foundation::Time::getCurrentCounterValue();
@@ -1147,15 +1147,17 @@ struct SApp : public IApplication
         }
 
         UpdatePresentations();
-        UpdateScenes();
+        bool dirty = UpdateScenes();
 
         // If subpresentations changed we need to check if any of them needs to be loaded.
         if (LazyLoadSubPresentations()) {
             // Just redo all
             UpdatePresentations();
-            UpdateScenes();
+            dirty |= UpdateScenes();
         }
-
+        bool renderNextFrame = false;
+        if (m_LastRenderWasDirty || dirty || m_initialFrame)
+            renderNextFrame = true;
         Render();
 
         m_InputEnginePtr->ClearInputFrame();
@@ -1185,6 +1187,7 @@ struct SApp : public IApplication
             ResetDirtyCounter();
         else
             m_DirtyCountdown = NVMax(0, m_DirtyCountdown - 1);
+        return renderNextFrame;
     }
 
     // hook this up to -layer-caching.
diff --git a/src/runtime/Qt3DSApplication.h b/src/runtime/Qt3DSApplication.h
index 72d88a1..ad447f7 100644
--- a/src/runtime/Qt3DSApplication.h
+++ b/src/runtime/Qt3DSApplication.h
@@ -174,7 +174,7 @@ public:
     virtual QList<Q3DStudio::CPresentation *> GetPresentationList() = 0;
 
     // Update all the presentations and render them.  Called exactly once per frame.
-    virtual void UpdateAndRender() = 0;
+    virtual bool UpdateAndRender() = 0;
 
     virtual bool IsApplicationDirty() = 0;
 
diff --git a/src/runtimerender/rendererimpl/Qt3DSRendererImpl.cpp b/src/runtimerender/rendererimpl/Qt3DSRendererImpl.cpp
index 0484390..104bd09 100644
--- a/src/runtimerender/rendererimpl/Qt3DSRendererImpl.cpp
+++ b/src/runtimerender/rendererimpl/Qt3DSRendererImpl.cpp
@@ -253,7 +253,7 @@ namespace render {
             SLayerRenderData *theRenderData = GetOrCreateLayerRenderDataForNode(*theLayer, id);
 
             if (theRenderData) {
-                theRenderData->PrepareForRender();
+                bool needsRender = theRenderData->PrepareForRender();
                 if (id) {
                     if (m_initialPrepareData.contains(theLayer)) {
                         // Copy dirty state from the initial since the graph is
@@ -268,7 +268,8 @@ namespace render {
                         m_initialPrepareData.insert(theLayer, theRenderData);
                     }
                 }
-                retval = retval || theRenderData->m_LayerPrepResult->m_Flags.WasDirty();
+                retval = retval || needsRender
+                        || theRenderData->m_LayerPrepResult->m_Flags.WasDirty() ;
             } else {
                 QT3DS_ASSERT(false);
             }
diff --git a/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderData.cpp b/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderData.cpp
index c43ed1a..e453c91 100644
--- a/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderData.cpp
+++ b/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderData.cpp
@@ -120,9 +120,9 @@ namespace render {
         if (m_AdvancedBlendDrawTexture)
             m_AdvancedBlendDrawTexture = NULL;
     }
-    void SLayerRenderData::PrepareForRender(const QSize &inViewportDimensions)
+    bool SLayerRenderData::PrepareForRender(const QSize &inViewportDimensions)
     {
-        SLayerRenderPreparationData::PrepareForRender(inViewportDimensions);
+        bool needsRender = SLayerRenderPreparationData::PrepareForRender(inViewportDimensions);
         SLayerRenderPreparationResult &thePrepResult(*m_LayerPrepResult);
         IResourceManager &theResourceManager(m_Renderer.GetQt3DSContext().GetResourceManager());
 
@@ -182,6 +182,9 @@ namespace render {
             m_Renderer.GetQt3DSContext().GetEffectSystem().GetResourceManager()
                     .DestroyFreeSizedResources();
         }
+        bool isProgressiveAABlendPass =
+            m_ProgressiveAAPassIndex && m_ProgressiveAAPassIndex < thePrepResult.m_MaxAAPassIndex;
+        return needsRender || isProgressiveAABlendPass;
     }
 
     NVRenderTextureFormats::Enum SLayerRenderData::GetDepthBufferFormat()
@@ -2328,13 +2331,13 @@ void SLayerRenderData::RunRenderPass(TRenderRenderableFunction inRenderFn,
                 QSize(theCurrentViewport.m_Width, theCurrentViewport.m_Height));
     }
 
-    void SLayerRenderData::PrepareForRender()
+    bool SLayerRenderData::PrepareForRender()
     {
         // When we render to the scene itself (as opposed to an offscreen buffer somewhere)
         // then we use the MVP of the layer somewhat.
         NVRenderRect theViewport = m_Renderer.GetQt3DSContext().GetRenderList().GetViewport();
-        PrepareForRender(
-            QSize((QT3DSU32)theViewport.m_Width, (QT3DSU32)theViewport.m_Height));
+        return PrepareForRender(
+                    QSize((QT3DSU32)theViewport.m_Width, (QT3DSU32)theViewport.m_Height));
     }
 
     void SLayerRenderData::ResetForFrame()
diff --git a/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderData.h b/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderData.h
index aa4d456..7520edf 100644
--- a/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderData.h
+++ b/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderData.h
@@ -102,10 +102,10 @@ struct AdvancedBlendModes
 
         virtual ~SLayerRenderData();
 
-        void PrepareForRender();
+        bool PrepareForRender();
 
         // Internal Call
-        void PrepareForRender(const QSize &inViewportDimensions) override;
+        bool PrepareForRender(const QSize &inViewportDimensions) override;
 
         NVRenderTextureFormats::Enum GetDepthBufferFormat();
         NVRenderFrameBufferAttachments::Enum
diff --git a/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderPreparationData.cpp b/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderPreparationData.cpp
index 1f191b0..821a0b8 100644
--- a/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderPreparationData.cpp
+++ b/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderPreparationData.cpp
@@ -1219,12 +1219,12 @@ namespace render {
         }
     };
 
-    void SLayerRenderPreparationData::PrepareForRender(const QSize &inViewportDimensions)
+    bool SLayerRenderPreparationData::PrepareForRender(const QSize &inViewportDimensions)
     {
         QT3DS_PERF_SCOPED_TIMER(m_Renderer.GetQt3DSContext().GetPerfTimer(),
                                 "LayerRenderData: PrepareForRender")
         if (m_LayerPrepResult.hasValue())
-            return;
+            return false;
 
         m_Features.clear();
         m_FeatureSetHash = 0;
@@ -1576,6 +1576,7 @@ namespace render {
         GetTransparentRenderableObjects();
 
         GetCameraDirection();
+        return wasDirty;
     }
 
     void SLayerRenderPreparationData::ResetForFrame()
diff --git a/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderPreparationData.h b/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderPreparationData.h
index 53b60f2..8b1463a 100644
--- a/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderPreparationData.h
+++ b/src/runtimerender/rendererimpl/Qt3DSRendererImplLayerRenderPreparationData.h
@@ -344,7 +344,7 @@ namespace render {
 
         // returns true if this object will render something different than it rendered the last
         // time.
-        virtual void PrepareForRender(const QSize &inViewportDimensions);
+        virtual bool PrepareForRender(const QSize &inViewportDimensions);
         bool CheckLightProbeDirty(SImage &inLightProbe);
         void AddRenderWidget(IRenderWidget &inWidget);
         void SetShaderFeature(const char *inName, bool inValue);
diff --git a/src/viewer/Qt3DSViewerApp.cpp b/src/viewer/Qt3DSViewerApp.cpp
index a4cec7f..ce8163f 100644
--- a/src/viewer/Qt3DSViewerApp.cpp
+++ b/src/viewer/Qt3DSViewerApp.cpp
@@ -522,8 +522,9 @@ void Q3DSViewerApp::setupSearchPath(std::vector<std::string> &cmdLineArgs)
     //NvFAppendSearchPath(theModuleDirectory.c_str());
 }
 
-void Q3DSViewerApp::Render()
+bool Q3DSViewerApp::Render()
 {
+    bool ret = true;
     if (m_Impl.m_view && m_Impl.m_view->GetTegraRenderEngine()) {
         if (m_Impl.m_appInitSuccessful) {
             for (QEvent *e : m_Impl.m_pendingEvents) {
@@ -535,9 +536,10 @@ void Q3DSViewerApp::Render()
             HandleController(*m_Impl.m_view);
 #endif
 
-            m_Impl.m_view->Render();
+            ret = m_Impl.m_view->Render();
         }
     }
+    return ret;
 }
 
 void Q3DSViewerApp::SaveState()
diff --git a/src/viewer/Qt3DSViewerApp.h b/src/viewer/Qt3DSViewerApp.h
index 25d2ed7..db8ba57 100644
--- a/src/viewer/Qt3DSViewerApp.h
+++ b/src/viewer/Qt3DSViewerApp.h
@@ -257,9 +257,9 @@ public:
     /*
      * @brief does the actual scene rendering
      *
-     * @return no return
+     * @return true if the scene needs to be rendered again in next frame
      */
-    void Render();
+    bool Render();
 
     /*
      * @brief handle keyboard input