Logging and Debugging

Logging

LogFusion is the log category declared in FusionShared.h. Every plugin-side message lands here, so filtering the Output Log by LogFusion is the fastest way to see what Fusion is doing.

Configuring Fusion Log Levels and Outputs

Fusion specific log levels can be configured in the Logging section of the Fusion Settings in the Project Settings.

Enabling On Screen Debug Message Log Output in the Enabled Log Output section routes Fusion log calls through FusionOnScreenDebugMessageLogOutput. Messages surface as viewport debug messages alongside their Output Log entries — useful for spotting events during play without watching the log window.

Combine the on-screen sink with a restrictive EnabledLogLevels (for example Warning | Error only) to keep the overlay readable. Trace and Debug entries multiply quickly during a PIE session and will overflow the viewport if all severities are forwarded on-screen.

Editor Debug Panels

The Fusion Debug Tools can be found at the bottom of the Windows menu in the editor in the Photon section.

This panel captures bandwidth and string heap information for every connected PIE window.

The bandwidth section shows per-object send and receive information over time as sortable trees. Use it to spot the heaviest replicators in a session - typically the right starting point for "why is bandwidth high" debugging.

CVars

Fusion's runtime CVars are registered in FusionOnlineSubsystem.cpp and back the externs declared in FusionCVars.h. They are set the standard Unreal way: from the in-game console, from a .ini file, or via IConsoleManager from C++.