April 23rd, 2021

• Single camera via camera manager in UE4

ue-editor

• Having custom editor only objects appear is quite a task overall

  • CameraComponent is a good example of how it is done in source code:
    • Engine\UE4\Source\Runtime\Engine\Classes\Camera\CameraComponent.h : 149. This header contains the editor driven functions for creating an managing the proxy mesh that represents the camera positioning in the Blueprint Editor.
    • Powered by a ProxyMeshComponent, it is updated when OnRegister is called. Here a new Mesh is created, setup and other calls to update the position is called.

• Responding to changes in the is done in a few places.

  • To Respond to an editor proprety change (Like a input field), use PostEditChangeProperty(FPropertyChangedEvent& PropertyChangedEvent)

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#if WITH\_EDITORONLY\_DATA  
void UCameraComponent::PostEditChangeProperty(FPropertyChangedEvent & PropertyChangedEvent)  
{  
   Super::PostEditChangeProperty(PropertyChangedEvent);  
  
   const FName PropertyName \= PropertyChangedEvent.Property ? PropertyChangedEvent.Property\->GetFName() : FName();  
   if (PropertyName \== GET\_MEMBER\_NAME\_CHECKED(UCameraComponent, bCameraMeshHiddenInGame))  
   {  
      OnCameraMeshHiddenChanged();  
   }  
  
   RefreshVisualRepresentation();  
}
#endif

• For ActorComponents Override OnRegister as this is called after a proprerty change

• WITH_EDITOR vs WITH_EDITOR_DATA

  • According to https://forums.unrealengine.com/t/with_editor-vs-with_editoronly_data-need-clarification/103182/6

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WITH\_EDITORONLY\_DATA tells the Header tool to Add serialization code for those fields WHEN BUILDING EDITOR TIME TOOLS.

AND STRIPS the data IN SHIPPING GAME BUILDS.WITH\_EDITOR id a compiler directive. WITH\_EDITORONLY\_DATA is a header tool directive.	

• Component Visualisers
  • Used by components such as USpringArmCmponent to visualise the target arm length when selected
    • FComponentVisualizer is a base class that is extended.
    • Provides a draw method that will be called in the editor when the object is selected. Here you can provide debug draw / other draw types
    • The Visualiser has to be registered with the editor on module start up so it is best suited to be in the an Editor module
    • https://sondreutheim.com/post/ue4_component_visualizers

• Get a base project up and to get a component visualiser up as well as try and understand how to draw and update objects in the editor after property change.