fix mesh 3D level of detail slide bar

src/app/3d/qgsmesh3dsymbolwidget.cpp

@@ -81,7 +81,7 @@ void QgsMesh3dSymbolWidget::setSymbol( const QgsMesh3DSymbol *symbol )
   mGroupBoxWireframe->setChecked( symbol->wireframeEnabled() );
   mColorButtonWireframe->setColor( symbol->wireframeLineColor() );
   mSpinBoxWireframeLineWidth->setValue( symbol->wireframeLineWidth() );
-  if ( mLayer )
+  if ( mLayer && mLayer->meshSimplificationSettings().isEnabled() )
     mLodSlider->setValue( mLayer->triangularMeshLevelOfDetailCount() - symbol->levelOfDetailIndex() - 1 );
   else
     mLodSlider->setValue( mLodSlider->maximum() );
@@ -128,16 +128,15 @@ void QgsMesh3dSymbolWidget::setLayer( QgsMeshLayer *meshLayer, bool updateSymbol
 
   if ( meshLayer && meshLayer->meshSimplificationSettings().isEnabled() )
   {
-    mLodSlider->setVisible( true );
-    mLabelLod->setVisible( true );
+    mLodSlider->setEnabled( true );
     int lodCount = meshLayer->triangularMeshLevelOfDetailCount();
     mLodSlider->setTickInterval( 1 );
     mLodSlider->setMaximum( lodCount - 1 );
   }
   else
   {
-    mLodSlider->setVisible( false );
-    mLabelLod->setVisible( false );
+    mLodSlider->setValue( mLodSlider->maximum() );
+    mLodSlider->setEnabled( false );
   }
 
   if ( !updateSymbol )

src/ui/3d/qgsmesh3dpropswidget.ui

@@ -103,6 +103,12 @@
       </item>
       <item row="2" column="1" colspan="2">
        <widget class="QSlider" name="mLodSlider">
+        <property name="toolTip">
+         <string>Need mesh simplification</string>
+        </property>
+        <property name="value">
+         <number>99</number>
+        </property>
         <property name="orientation">
          <enum>Qt::Horizontal</enum>
         </property>
@@ -406,6 +412,12 @@
   </layout>
  </widget>
  <customwidgets>
+  <customwidget>
+   <class>QgsColorRampShaderWidget</class>
+   <extends>QWidget</extends>
+   <header>raster/qgscolorrampshaderwidget.h</header>
+   <container>1</container>
+  </customwidget>
   <customwidget>
    <class>QgsCollapsibleGroupBox</class>
    <extends>QGroupBox</extends>
@@ -423,12 +435,6 @@
    <header>qgscolorbutton.h</header>
    <container>1</container>
   </customwidget>
-  <customwidget>
-   <class>QgsColorRampShaderWidget</class>
-   <extends>QWidget</extends>
-   <header>raster/qgscolorrampshaderwidget.h</header>
-   <container>1</container>
-  </customwidget>
  </customwidgets>
  <tabstops>
   <tabstop>mChkSmoothTriangles</tabstop>