Unreal - Logging

General logging Macro with configurable category and verbosity.

• UE_LOG(LogTemp, Warning, TEXT("We %s hit %s"), *actor_name, *our_name);
  • LogTemp and Warning are the Category and Verbosity Mask. See engine source Engine\Source\Runtime\Core\Public\Logging\LogVerbosity.h for listings
  • The text portion can use printf specifiers
  • when passing FString, remember to dereference them so the log can use the underlaying TCHAR,
• Verbosity levels :
  • NoLogging,  Fatal, Error, Warning, Display, Log, Verbose, VeryVerbose, All,  VerbosityMask,  SetColor,  BreakOnLog,     
  • Docs: https://docs.unrealengine.com/en-US/API/Runtime/Core/Logging/ELogVerbosity__Type/index.html

• In the header: DECLARE_LOG_CATEGORY_EXTERN(LogCatName, DefaultVerbosity, CompileTimeVerbosity)

• in the implimentation file DEFINE_LOG_CATEGORY(LogCatName)

• You should also be able to define these in blunk in a common header, in order to use a more common category without including unrelated files.

• Returns an FString, so when logging make sure to dereference!
  • UE_LOG(LogCat, LogType, TEXT("This is enum %s"), *UEnum::GetValueAsName(value).ToString())

Logging macros that export data to the ue-visual-logger allow collection and display of debug data over time.

• UE_VLOG_LOCATION(AActor* Owner, Category, Verbosity, TEXT("Format"), VarArgs.. )

• Other Varients exist

  • UE_VLOG_ARROW - Draw a debug Arrow
  • UE\_VLOG_\SEGMENT / _THICK - Draw a line / thick line
  • UE\_VLOG\_CONE / BOX / CAPSULE - Draw Shapes
  • Check Visual logger docs for more: https://docs.unrealengine.com/en-US/TestingAndOptimization/VisualLogger/index.html

• Can be wrapped with [[if]] ENABLE_VISUAL_LOG

It can be useful the see logs in a shipping build but not in game as the build process is different and can quite often have changes that do not happen in editor.

To enable output logs in shipping:

• Add the following to your modules build target:

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// enable logs and debugging for Shipping builds  
if (Configuration \== UnrealTargetConfiguration.Shipping)  
{  
 BuildEnvironment \= TargetBuildEnvironment.Unique;  
 bUseChecksInShipping \= true;  
 bUseLoggingInShipping \= true;  

• Run the build exe with -Log as an argument
  • Build.exe -Log