Improve 3D Map View movement performance

src/3d/qgs3dmapscene.cpp

@@ -334,8 +334,7 @@ void Qgs3DMapScene::updateScene( bool forceUpdate )
     return;
   }
 
-  if ( forceUpdate )
-    QgsEventTracing::addEvent( QgsEventTracing::Instant, QStringLiteral( "3D" ), QStringLiteral( "Update Scene" ) );
+  QgsEventTracing::ScopedEvent traceEvent( QStringLiteral( "3D" ), forceUpdate ? QStringLiteral( "Force update scene" ) : QStringLiteral( "Update scene" ) );
 
   Qgs3DMapSceneEntity::SceneContext sceneContext;
   Qt3DRender::QCamera *camera = mEngine->camera();
@@ -421,6 +420,8 @@ bool Qgs3DMapScene::updateCameraNearFarPlanes()
 
 void Qgs3DMapScene::onFrameTriggered( float dt )
 {
+  QgsEventTracing::addEvent( QgsEventTracing::EventType::Instant, QStringLiteral( "3D" ), QStringLiteral( "Frame begins" ) );
+
   mCameraController->frameTriggered( dt );
 
   updateScene();

src/3d/qgs3dutils.cpp

@@ -45,6 +45,7 @@
 #include <Qt3DRender/QRenderSettings>
 #include <QOpenGLContext>
 #include <QOpenGLFunctions>
+#include <qframeaction.h>
 
 
 #if QT_VERSION < QT_VERSION_CHECK( 6, 0, 0 )
@@ -58,6 +59,17 @@ typedef Qt3DCore::QBuffer Qt3DQBuffer;
 // declared here as Qgs3DTypes has no cpp file
 const char *Qgs3DTypes::PROP_NAME_3D_RENDERER_FLAG = "PROP_NAME_3D_RENDERER_FLAG";
 
+static void waitForFrame( Qgs3DMapScene *scene )
+{
+  // Wait for at least one frame to render
+  Qt3DLogic::QFrameAction *frameAction = new Qt3DLogic::QFrameAction();
+  scene->addComponent( frameAction );
+  QEventLoop evLoop;
+  QObject::connect( frameAction, &Qt3DLogic::QFrameAction::triggered, &evLoop, &QEventLoop::quit );
+  evLoop.exec();
+  scene->removeComponent( frameAction );
+}
+
 QImage Qgs3DUtils::captureSceneImage( QgsAbstract3DEngine &engine, Qgs3DMapScene *scene )
 {
   QImage resImage;
@@ -66,13 +78,7 @@ QImage Qgs3DUtils::captureSceneImage( QgsAbstract3DEngine &engine, Qgs3DMapScene
   // We need to change render policy to RenderPolicy::Always, since otherwise render capture node won't work
   engine.renderSettings()->setRenderPolicy( Qt3DRender::QRenderSettings::RenderPolicy::Always );
 
-  auto requestImageFcn = [&engine, scene] {
-    if ( scene->sceneState() == Qgs3DMapScene::Ready )
-    {
-      engine.renderSettings()->setRenderPolicy( Qt3DRender::QRenderSettings::RenderPolicy::OnDemand );
-      engine.requestCaptureImage();
-    }
-  };
+  waitForFrame( scene );
 
   auto saveImageFcn = [&evLoop, &resImage]( const QImage &img ) {
     resImage = img;
@@ -82,6 +88,14 @@ QImage Qgs3DUtils::captureSceneImage( QgsAbstract3DEngine &engine, Qgs3DMapScene
   const QMetaObject::Connection conn1 = QObject::connect( &engine, &QgsAbstract3DEngine::imageCaptured, saveImageFcn );
   QMetaObject::Connection conn2;
 
+  auto requestImageFcn = [&engine, scene] {
+    if ( scene->sceneState() == Qgs3DMapScene::Ready )
+    {
+      engine.renderSettings()->setRenderPolicy( Qt3DRender::QRenderSettings::RenderPolicy::OnDemand );
+      engine.requestCaptureImage();
+    }
+  };
+
   if ( scene->sceneState() == Qgs3DMapScene::Ready )
   {
     requestImageFcn();
@@ -110,6 +124,8 @@ QImage Qgs3DUtils::captureSceneDepthBuffer( QgsAbstract3DEngine &engine, Qgs3DMa
   // We need to change render policy to RenderPolicy::Always, since otherwise render capture node won't work
   engine.renderSettings()->setRenderPolicy( Qt3DRender::QRenderSettings::RenderPolicy::Always );
 
+  waitForFrame( scene );
+
   auto requestImageFcn = [&engine, scene] {
     if ( scene->sceneState() == Qgs3DMapScene::Ready )
     {

src/3d/qgscameracontroller.cpp

@@ -15,6 +15,7 @@
 
 #include "qgscameracontroller.h"
 #include "moc_qgscameracontroller.cpp"
+#include "qgseventtracing.h"
 #include "qgsvector3d.h"
 #include "qgswindow3dengine.h"
 #include "qgs3dmapscene.h"
@@ -161,6 +162,12 @@ void QgsCameraController::zoomCameraAroundPivot( const QVector3D &oldCameraPosit
 void QgsCameraController::frameTriggered( float dt )
 {
   Q_UNUSED( dt )
+
+  if ( mCameraChanged )
+  {
+    emit cameraChanged();
+    mCameraChanged = false;
+  }
 }
 
 void QgsCameraController::resetView( float distance )
@@ -233,7 +240,7 @@ void QgsCameraController::readXml( const QDomElement &elem )
   setLookingAtPoint( QgsVector3D( x, elev, y ), dist, pitch, yaw );
 }
 
-double QgsCameraController::sampleDepthBuffer( const QImage &buffer, int px, int py )
+double QgsCameraController::sampleDepthBuffer( int px, int py )
 {
   double depth = 1;
 
@@ -242,24 +249,28 @@ double QgsCameraController::sampleDepthBuffer( const QImage &buffer, int px, int
   {
     for ( int y = py - 3; y <= py + 3; ++y )
     {
-      if ( buffer.valid( x, y ) )
+      if ( mDepthBufferImage.valid( x, y ) )
       {
-        depth = std::min( depth, Qgs3DUtils::decodeDepth( buffer.pixel( x, y ) ) );
+        depth = std::min( depth, Qgs3DUtils::decodeDepth( mDepthBufferImage.pixel( x, y ) ) );
       }
     }
   }
 
   if ( depth < 1 )
     return depth;
 
+  // Cache the computed depth, since averaging over all pixels can be expensive
+  if ( mDepthBufferNonVoidAverage != -1 )
+    return mDepthBufferNonVoidAverage;
+
   // Returns the average of depth values that are not 1 (void area)
   depth = 0;
   int samplesCount = 0;
-  for ( int x = 0; x < buffer.width(); ++x )
+  for ( int x = 0; x < mDepthBufferImage.width(); ++x )
   {
-    for ( int y = 0; y < buffer.height(); ++y )
+    for ( int y = 0; y < mDepthBufferImage.height(); ++y )
     {
-      double d = Qgs3DUtils::decodeDepth( buffer.pixel( x, y ) );
+      double d = Qgs3DUtils::decodeDepth( mDepthBufferImage.pixel( x, y ) );
       if ( d < 1 )
       {
         depth += d;
@@ -274,6 +285,8 @@ double QgsCameraController::sampleDepthBuffer( const QImage &buffer, int px, int
   else
     depth /= samplesCount;
 
+  mDepthBufferNonVoidAverage = depth;
+
   return depth;
 }
 
@@ -282,7 +295,7 @@ void QgsCameraController::updateCameraFromPose()
   if ( mCamera )
     mCameraPose.updateCamera( mCamera );
 
-  emit cameraChanged();
+  mCameraChanged = true;
 }
 
 void QgsCameraController::moveCameraPositionBy( const QVector3D &posDiff )
@@ -296,6 +309,8 @@ void QgsCameraController::onPositionChanged( Qt3DInput::QMouseEvent *mouse )
   if ( !mInputHandlersEnabled )
     return;
 
+  QgsEventTracing::ScopedEvent traceEvent( QStringLiteral( "3D" ), QStringLiteral( "QgsCameraController::onPositionChanged" ) );
+
   switch ( mCameraNavigationMode )
   {
     case Qgis::NavigationMode::TerrainBased:
@@ -310,7 +325,7 @@ void QgsCameraController::onPositionChanged( Qt3DInput::QMouseEvent *mouse )
 
 bool QgsCameraController::screenPointToWorldPos( QPoint position, Qt3DRender::QCamera *mCameraBefore, double &depth, QVector3D &worldPosition )
 {
-  depth = sampleDepthBuffer( mDepthBufferImage, position.x(), position.y() );
+  depth = sampleDepthBuffer( position.x(), position.y() );
   if ( !std::isfinite( depth ) )
   {
     QgsDebugMsgLevel( QStringLiteral( "screenPointToWorldPos: depth is NaN or Inf. This should not happen." ), 2 );
@@ -1017,6 +1032,7 @@ void QgsCameraController::depthBufferCaptured( const QImage &depthImage )
 {
   mDepthBufferImage = depthImage;
   mDepthBufferIsReady = true;
+  mDepthBufferNonVoidAverage = -1;
 
   if ( mCurrentOperation == MouseOperation::ZoomWheel )
   {

src/3d/qgscameracontroller.h

@@ -326,7 +326,7 @@ class _3D_EXPORT QgsCameraController : public QObject
      * Returns the minimum depth value in the square [px - 3, px + 3] * [py - 3, py + 3]
      * If the value is 1, the average depth of all non void pixels is returned instead.
      */
-    double sampleDepthBuffer( const QImage &buffer, int px, int py );
+    double sampleDepthBuffer( int px, int py );
 
 #ifndef SIP_RUN
     //! Converts screen point to world position
@@ -350,6 +350,9 @@ class _3D_EXPORT QgsCameraController : public QObject
 
     bool mDepthBufferIsReady = false;
     QImage mDepthBufferImage;
+    // -1 when unset
+    // TODO: Change to std::optional<double>
+    double mDepthBufferNonVoidAverage;
 
     std::unique_ptr<Qt3DRender::QCamera> mCameraBefore;
 
@@ -385,6 +388,9 @@ class _3D_EXPORT QgsCameraController : public QObject
     // 3D world's origin in map coordinates
     QgsVector3D mOrigin;
 
+    //! Did camera change since last frame? Need to know if we should emit cameraChanged().
+    bool mCameraChanged = false;
+
     // To test the cameracontroller
     friend class TestQgs3DRendering;
     friend class TestQgs3DCameraController;