AFrameGrabberActor::StartFrameGrab.cpp

bool  AFrameGrabberActor::StartFrameGrab() {
    TSharedPtr<FSceneViewport> SceneViewport;

    // Get SceneViewport
    // ( quoted from FRemoteSessionHost::OnCreateChannels() )
#if WITH_EDITOR
    if (GIsEditor) { 
        for (const FWorldContext& Context : GEngine->GetWorldContexts()) {
            if (Context.WorldType == EWorldType::PIE) {
                FSlatePlayInEditorInfo* SlatePlayInEditorSession = GEditor->SlatePlayInEditorMap.Find(Context.ContextHandle);
                if (SlatePlayInEditorSession) {
                    if (SlatePlayInEditorSession->DestinationSlateViewport.IsValid()) {
                        TSharedPtr<ILevelViewport> DestinationLevelViewport = SlatePlayInEditorSession->DestinationSlateViewport.Pin();
                        SceneViewport = DestinationLevelViewport->GetSharedActiveViewport();
                    }
                    else if (SlatePlayInEditorSession->SlatePlayInEditorWindowViewport.IsValid()) {
                        SceneViewport = SlatePlayInEditorSession->SlatePlayInEditorWindowViewport;
                    }
                }
            }
        }
    }
    else
#endif
    {
        UGameEngine* GameEngine = Cast<UGameEngine>(GEngine);
        SceneViewport = GameEngine->SceneViewport;
    }
    if (!SceneViewport.IsValid()) {
        return false;
    }

    // Setup Texture
    if (!CaptureFrameTexture) {
        CaptureFrameTexture = UTexture2D::CreateTransient(SceneViewport.Get()->GetSize().X, SceneViewport.Get()->GetSize().Y, PF_B8G8R8A8);
        CaptureFrameTexture->UpdateResource();
        
        MaterialInstanceDynamic->SetTextureParameterValue(FName("Texture"), CaptureFrameTexture);
    }
	
    // Capture Start
    ReleaseFrameGrabber();
    FrameGrabber = MakeShareable(new FFrameGrabber(SceneViewport.ToSharedRef(), SceneViewport->GetSize()));
    FrameGrabber->StartCapturingFrames();

    return true;
}