Customer Provided Description:

This was experienced in UE 5.01 - custom installed engine (No changes to UE code, simply added the Debug build configuration, see the following command):

"c:%ue_directory%\Engine\Build\BatchFiles\RunUAT.bat" ^
BuildGraph ^
-target="Make Installed Build Win64" ^
-script="c:%ue_directory%\Engine\Build\InstalledEngineBuild.xml" ^
-set:GameConfigurations=Development;Shipping;Debug ^
-set:WithFullDebugInfo=true ^
-set:WithWin64=true ^
-set:WithMac=false ^
-set:WithWin32=false ^
-set:WithIOS=false ^
-set:WithAndroid=false ^
-set:WithTVOS=false ^
-set:WithHTML5=false ^
-set:WithLumin=false ^
-set:WithPS4=false ^
-set:WithXboxOne=false ^
-set:WithLinux=false ^
-set:WithLinuxArm64=false ^

I first noticed this in my own project when building in Debug mode - it persisted even after I removed all user-defined content from the world outliner and disabled all user code which touch FVectors. So I tried to repeat the process on a new empty project and discovered that it is reproducible in that context, too.

This error is not debugable since, either due to FORCEINLINE or ENABLE_NAN_DIAGNOSTIC, a breakpoint either can't be set on it (VS) or is not honored during debug runs (Rider). I spent a great deal of time trying to find the cause of this issue because I wanted to resolve it to ensure that it was not contributing to another problem I'm facing in my project - it has taken a long time to narrow down the conditions under which it emits.

The error appears to emit for all packaged Debug builds - this should be fixed.

Also, the error should be attributable to specific engine or user code. Currently, there is no way to discover where it comes from. I spent too long tracking this down, initially thinking it was related to some other problem I am facing in my project.

This was also tested in normal workflow with source build and this issued DID Happen.

This is a regression.

Steps to Reproduce
  1. have a source build workspace or Locally installed build
    • if local installed build being used, make it with command:
      Engine\Build\BatchFiles\RunUAT.bat BuildGraph -target="Make Installed Build Win64" -script=Engine\Build\InstalledEngineBuild.xml -set:GameConfigurations=Development;Shipping;Debug -set:WithFullDebugInfo=true -set:WithWin64=true -set:WithMac=false -set:WithWin32=false -set:WithIOS=false -set:WithAndroid=false -set:WithTVOS=false -set:WithHTML5=false -set:WithLumin=false -set:WithPS4=false -set:WithXboxOne=false -set:WithLinux=false -set:WithLinuxArm64=false -set:WithHoloLens=false
  2. Create a Blank C++ project
  3. package the project in Debug Configuration for Windows
  4. run the Debug package executable for 5-10 seconds
  5. Inspect logs for Debug package executable

Expected Results: No errors or warnings about FVector

Actual Results: logs show error:

Error: FVector contains NaN: X=-inf Y=-inf Z=-inf

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ComponentUE - Rendering - Lumen
Affects Versions5.0.1
Target Fix5.1
CreatedMay 6, 2022
ResolvedJun 17, 2022
UpdatedJun 21, 2022