If a function takes in an FQuat value and then multiplies it by an FQuat, the project will build properly but then crash when trying to launch the project in the editor.

Example project available but too large to submit.

Steps to Reproduce

1. Open UE4 Editor
2. Add code to project based on GameMode
3. In the .h file, add the following code:

static FRotator GetConversionRotator()
		const auto mineToUE4 = FRotator::MakeFromEuler(FVector(-90, 0, 90));
		return mineToUE4;

	FQuat ConvertToUe4Rotation(FQuat inputQuat)
		const FQuat rotQuat = FQuat(GetConversionRotator());
		const FQuat newQuat = inputQuat * rotQuat;
		return newQuat;

4. In the .cpp, add the following code:

	FQuat xformRot = FQuat::Identity;
	//...populate xformRot here maybe
	xformRot = ConvertToUe4Rotation(xformRot);

5. Build the project in Development Editor
6. In the project folder, launch the .uproject file.

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Won't Fix
CreatedNov 5, 2014
ResolvedFeb 17, 2015
UpdatedJul 14, 2021
View Jira Issue