Variables in Unreal Engine

Variables in Unreal Engine

• bool - boolean values (NEVER assume the size of bool). BOOL will not compile.
• TCHAR - character (NEVER assume the size of TCHAR).

• Numerical values

  • Integers

    int and unsigned int types—whose size may vary across platforms, but which is guaranteed to be at least 32 bits in width—is acceptable in code where the integer width is unimportant. Explicitly-sized types must still be used in serialized or replicated formats.

    Type	Kind	Size	Range	Exposed to BP
    int8	8 bit signed integer	+/- 128	1 byte	false
    uint8	8 bit unsigned integer	0 - 255	1 byte	true
    int16	16 bit signed "shorts"	+/- 32,768	2 bytes	false
    uint16	16 bit unsigned "shorts"	0 - 65,535	2 bytes	false
    int32	32 bit signed ints	+/- 2,147,483,647	4 bytes	true
    uint32	32 bit unsigned ints	0 - 4,294,967,295	4 bytes	false
    int64	64 bit signed "quad words"	+/- 9,223,372,036,854,775,807	8 bytes	true
    uint64	64 bit unsigned "quad words"	0 - 18,446,744,073,709,551,615	8 bytes	false

    • PTRINT for an integer that may hold a pointer (NEVER assume the size of PTRINT).
    • FScalableFloat - Generic numerical value in the form Value * Curve[Level]
  • float for single precision floating point (4 bytes).
  • double for double precision floating point (8 bytes).

  • Vectors

    Based on the accurancy you need, you can use the following:

    Type	Kind	Size	Range	Exposed to BP
    FVector_NetQuantizeNormal	Vector (x,y,z)	+/- 1	12 bytes / 2 bytes	true
    FVector_NetQuantize	Vector (x,y,z) - 0 decimal place of precision	+/- 1,048,576	12 bytes / 2.5 bytes
    FVector_NetQuantize10	Vector (x,y,z) - 1 decimal place of precision	+/- 1,677,721.6	12 bytes / 3 bytes
    FVector_NetQuantize100	Vector (x,y,z) - 2 decimal place of precision	+/- 10,737,418.24	12 bytes / 3.75 bytes
    FVector	Vector (x,y,z) - 6 decimal place of precision	+/- 3.4E+38	12 bytes / 12 bytes

  • Components - Variables can point (keep address) to any component and thus be type of any component.

• Text values

  • FName [12 bytes] - Provide a very lightweight system for using strings, where a given string is stored only once in a data table

    FNames are inherently fast, if used correctly - avoid doing of if (ActorHasTag(TEXT("MyFNameActor_Tag"))) ... which makes temporary conversion of FName to FString. Use something like following, that does not make conversion, uses FName and is roughtly 100x faster:

    static const FName NAME_MyFNameActor(TEXT("MyFNameActor_Tag"));
    if (ActorHasTag(NAME_MyFNameActor))

    The second code defines a static FName instance named NAME_MyFNameActor. This instance is created only once and exists for the entire runtime of the program. No need to create a new tag comparison string; instead, two internal FName identifiers are compared, which is faster and more memory efficient.

  • FText [16 bytes] - Primary component for text localization - All user-facing text should use this class, as it supports text localization
  • FString [24 bytes] - Unlike FName and FText, FString can be searched, modified, and compared against other strings. However, these manipulations can make FStrings more expensive than the immutable string classes.