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.