1. Epic GamesDeveloper
  3. FEmitter

FEmitter

The [FEmitter](API\Runtime\Engine\FEmitter) is a helper object responsible for emitting MIR values and instructions.

API > API/Runtime > API/Runtime/Engine

The FEmitter is a helper object responsible for emitting MIR values and instructions. It is primarily used within UMaterialExpression::Build() implementations to lower the high-level semantics of a material expression into corresponding lower-level MIR nodes.

During the emission process, the emitter automatically performs various simplifications and constant folding optimizations where possible.

An instance of the emitter is created and managed by the FMaterialIRModuleBuilder. This instance is then passed to the UMaterialExpression::Build() functions so that they can emit their corresponding IR values.

IMPORTANT: Users should not assume the exact MIR::FType of the FValue* returned by EmitXXX() functions. The emitter is free to optimize operations, which may result in a returned value having a different type than naively expected (e.g., folding an operation into a constant).

The emitter handles invalid inputs gracefully. If an operation is attempted with invalid arguments (e.g., acting on arguments of unexpected types), the emitter automatically reports an error and returns the MIR::FPoison value. Furthermore, all EmitXXX() functions are robust to receiving MIR::FPoison as input; they will simply propagate the poison value without attempting the operation.

   
Name FEmitter
Type class
Header File /Engine/Source/Runtime/Engine/Public/Materials/MaterialIREmitter.h
Include Path #include "Materials/MaterialIREmitter.h"

Syntax

class FEmitter

Constructors

Name Remarks Include Path Unreal Specifiers

FEmitter()

   Materials/MaterialIREmitter.h  

Structs

Name Remarks
FPrivate  
FValueKeyFuncs  

Variables

Protected

Name Type Remarks Include Path Unreal Specifiers
bCurrentExpressionHasErrors bool Whether the current expression has reported any error. Materials/MaterialIREmitter.h  
BuilderImpl FMaterialIRModuleBuilderImpl * Pointer to the builder internal implementation. Materials/MaterialIREmitter.h  
Expression UMaterialExpression * The current expression being built (set by the builder). Materials/MaterialIREmitter.h  
FalseConstant FValue * Global "false" constant. Materials/MaterialIREmitter.h  
FMaterialIRModuleBuilder friend   Materials/MaterialIREmitter.h  
FMaterialIRModuleBuilderImpl friend   Materials/MaterialIREmitter.h  
Material UMaterial * The material being translated. Materials/MaterialIREmitter.h  
Module FMaterialIRModule * The IR module being built. Materials/MaterialIREmitter.h  
StaticParameterSet const FStaticParameterSet * The set of static parameter assignments to use during this translation. Materials/MaterialIREmitter.h  
TrueConstant FValue * Global "true" constant. Materials/MaterialIREmitter.h  
ValueSet TSet< FValue *, FValueKeyFuncs > The set of all values previously emitted. Materials/MaterialIREmitter.h  

Functions

Public

Name Remarks Include Path Unreal Specifiers

FValueRef Abs ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef ACos ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef ACosh ( FValueRef A
)

   Materials/MaterialIREmitter.h  
  Materials/MaterialIREmitter.h  

FValueRef AnalyticalPartialDerivative ( FValueRef Value,
EDerivativeAxis Axis
)

 Computes and emits the analytical partial derivative of a give value. Materials/MaterialIREmitter.h  
  Materials/MaterialIREmitter.h  

FValueRef ASin ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef ASinh ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef ATan ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef ATanh ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef BitShiftLeft ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  

FValueRef BitShiftRight ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  

FValueRef BitwiseAnd ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  

FValueRef BitwiseNot ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef BitwiseOr ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  

FValueRef Branch ( FValueRef Condition,
FValueRef True,
FValueRef False
)

 Emits a branch instruction. Materials/MaterialIREmitter.h  

FValueRef Cast ( FValueRef Value,
const FType* TargetType
)

 Casts the given value to the specified target type. Returns poison if the cast is invalid. Materials/MaterialIREmitter.h  

FValueRef CastToBool ( FValueRef Value,
int NumRows
)

 These functions cast the given value to the a primitive scalar or column vector type of given rows. Materials/MaterialIREmitter.h  

FValueRef CastToFloat ( FValueRef Value,
int NumRows
)

   Materials/MaterialIREmitter.h  

FValueRef CastToInt ( FValueRef Value,
int NumRows
)

   Materials/MaterialIREmitter.h  
Casts the given arithmetic value to a scalar. Materials/MaterialIREmitter.h  

FValueRef Ceil ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef CheckIsArithmetic ( FValueRef Value
)

 Validates that the value is of an arithmetic type (int or float). Reports error and returns poison otherwise. Materials/MaterialIREmitter.h  

FValueRef CheckIsInteger ( FValueRef Value
)

 Validates that the value is of a integral type. If not, reports an error and returns poison. Materials/MaterialIREmitter.h  

FValueRef CheckIsPrimitive ( FValueRef Value
)

 Validates that the value is of a primitive type. If not, reports an error and returns poison. Materials/MaterialIREmitter.h  

FValueRef CheckIsScalar ( FValueRef Value
)

 Validates that the value is a scalar. If not, reports error and returns poison. Materials/MaterialIREmitter.h  

FValueRef CheckIsScalarOrVector ( FValueRef Value
)

 Validates that the value is either a scalar or a vector. Reports error and returns poison otherwise. Materials/MaterialIREmitter.h  
Retrieves the texture value flowing into given input. Materials/MaterialIREmitter.h  
Retrieves the value from the given input of given type kind. Materials/MaterialIREmitter.h  
  Materials/MaterialIREmitter.h  

FValueRef ConstantBool ( bool InX
)

 Returns the given constant boolean scalar. Materials/MaterialIREmitter.h  

FValueRef ConstantFalse()

 Returns the constant boolean scalar `false_. Materials/MaterialIREmitter.h  

FValueRef ConstantFloat ( TFloat InX
)

 Returns the given constant float scalar. Materials/MaterialIREmitter.h  

FValueRef ConstantFloat2 ( UE::Math::TVector2< TFloat > InValue
)

 Emits a constant float 2D column vector and returns it. Materials/MaterialIREmitter.h  

FValueRef ConstantFloat3 ( UE::Math::TVector< TFloat > InValue
)

 Emits a constant float 3D column vector and returns it. Materials/MaterialIREmitter.h  

FValueRef ConstantFloat4 ( UE::Math::TVector4< TFloat > InValue
)

 Emits a constant float 4D column vector and returns it. Materials/MaterialIREmitter.h  

FValueRef ConstantFromShaderValue ( const UE::Shader::FValue& InValue
)

 Converts the given UE::Shader::FValue to a MIR constant value and returns it. Materials/MaterialIREmitter.h  

FValueRef ConstantInt ( TInteger InX
)

 Returns the given constant integer scalar. Materials/MaterialIREmitter.h  

FValueRef ConstantInt2 ( UE::Math::TIntVector2< TInteger > InValue
)

 Emits a constant integer 2D column vector and returns it. Materials/MaterialIREmitter.h  

FValueRef ConstantInt3 ( UE::Math::TIntVector3< TInteger > InValue
)

 Emits a constant integer 3D column vector and returns it. Materials/MaterialIREmitter.h  

FValueRef ConstantInt4 ( UE::Math::TIntVector4< TInteger > InValue
)

 Emits a constant integer 4D column vector and returns it. Materials/MaterialIREmitter.h  

FValueRef ConstantOne ( EScalarKind Kind
)

 Emits a scalar constant value of given kind with value 1 and returns it. Materials/MaterialIREmitter.h  

FValueRef ConstantScalar ( EScalarKind Kind,
TFloat FromFloat
)

 Casts the given float value to the given scalar kind and returns its value. Materials/MaterialIREmitter.h  

FValueRef ConstantTrue()

 Returns the constant boolean scalar `true_. Materials/MaterialIREmitter.h  

FValueRef ConstantZero ( EScalarKind Kind
)

 Emits a scalar constant value of given kind with value 0 and returns it. Materials/MaterialIREmitter.h  

FValueRef Cos ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef Cosh ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef Cross ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  
Returns whether the current expression generated an error. Materials/MaterialIREmitter.h  

FValueRef CustomPrimitiveData ( uint32 PrimitiveDataIndex
)

 Emits a custom primitive data value with given index. Materials/MaterialIREmitter.h  

FValueRef Divide ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  
  Materials/MaterialIREmitter.h  

FValueRef Equals ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  

void Error ( FValueRef Source,
FStringView Message
)

 Reports an error with given error message. Materials/MaterialIREmitter.h  

void Error ( FStringView Message
)

 Reports an error with given error message. Materials/MaterialIREmitter.h  

void Errorf ( FValueRef Source,
UE::Core::TCheckedFormatString< FString::FmtCharType, TArgs... > Format,
TArgs... Args
)

 Reports an error using printf-like format and arguments to format the error message. Materials/MaterialIREmitter.h  

void Errorf ( UE::Core::TCheckedFormatString< FString::FmtCharType, TArgs... > Format,
TArgs... Args
)

 Reports an error using printf-like format and arguments to format the error message. Materials/MaterialIREmitter.h  

FValueRef Exponential ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef Exponential2 ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef ExternalInput ( EExternalInput Id
)

 Emits an external input value of given input Id and returns it. Materials/MaterialIREmitter.h  

FValueRef Floor ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef Fmod ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  

FValueRef Frac ( FValueRef A
)

   Materials/MaterialIREmitter.h  

const FType * GetCommonType ( const FType* A,
const FType* B
)

 Gets the common type between A and B and reports an error if no such type exists. Materials/MaterialIREmitter.h  

FValueRef GreaterThan ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  

FValueRef GreaterThanOrEquals ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  

FValueRef InlineHLSL ( const FMaterialExternalCodeDeclaration* InExternalCodeDeclaration,
TConstArrayView< FValueRef > InputValues,
EValueFlags ValueFlags,
EGraphProperties UsedGraphProperties
)

 Emit a new HLSL function inline within the material shader based on an external code declaration. Materials/MaterialIREmitter.h  

FValueRef InlineHLSL ( const FType* Type,
FString Code,
TConstArrayView< FValueRef > InputValues,
EValueFlags ValueFlags,
EGraphProperties UsedGraphProperties
)

 Emit a new HLSL function inline within the material shader. Materials/MaterialIREmitter.h  

FValueRef Input ( const FExpressionInput* Input
)

 Retrieves the value flowing into given input. Materials/MaterialIREmitter.h  

FValueRef InputDefaultBool ( const FExpressionInput* Input,
bool Default
)

 If the input has no value flowing in (e.g., because the input is disconnected), these DefaultXXX() functions will emit a constant value, bind it to the input, and return it. Materials/MaterialIREmitter.h  

FValueRef InputDefaultFloat ( const FExpressionInput* Input,
TFloat Default
)

   Materials/MaterialIREmitter.h  

FValueRef InputDefaultFloat2 ( const FExpressionInput* Input,
UE::Math::TVector2< TFloat > Default
)

   Materials/MaterialIREmitter.h  

FValueRef InputDefaultFloat3 ( const FExpressionInput* Input,
UE::Math::TVector< TFloat > Default
)

   Materials/MaterialIREmitter.h  

FValueRef InputDefaultFloat4 ( const FExpressionInput* Input,
UE::Math::TVector4< TFloat > Default
)

   Materials/MaterialIREmitter.h  

FValueRef InputDefaultInt ( const FExpressionInput* Input,
TInteger Default
)

   Materials/MaterialIREmitter.h  

FValueRef InputDefaultInt2 ( const FExpressionInput* Input,
UE::Math::TIntVector2< TInteger > Default
)

   Materials/MaterialIREmitter.h  

FValueRef InputDefaultInt3 ( const FExpressionInput* Input,
UE::Math::TIntVector3< TInteger > Default
)

   Materials/MaterialIREmitter.h  

FValueRef InputDefaultInt4 ( const FExpressionInput* Input,
UE::Math::TIntVector4< TInteger > Default
)

   Materials/MaterialIREmitter.h  

FValueRef Length ( FValueRef A
)

   Materials/MaterialIREmitter.h  
  Materials/MaterialIREmitter.h  

FValueRef LessThan ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  

FValueRef LessThanOrEquals ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  

FValueRef Logarithm ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef Logarithm10 ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef Logarithm2 ( FValueRef A
)

   Materials/MaterialIREmitter.h  
  Materials/MaterialIREmitter.h  
  Materials/MaterialIREmitter.h  

FValueRef Multiply ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  

FValueRef Negate ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef Not ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef NotEquals ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  
Emits a mathematical operation instruction with given operator and arguments. Materials/MaterialIREmitter.h  
  Materials/MaterialIREmitter.h  

FEmitter & Output ( int32 OutputIndex,
FValueRef Value
)

 Flows given Value_ out of the expression output with given OutputIndex_. Materials/MaterialIREmitter.h  

FEmitter & Output ( const FExpressionOutput* Output,
FValueRef Value
)

 Flows given Value_ out of given expression Output_. Materials/MaterialIREmitter.h  

FValueRef Parameter ( FName Name,
FMaterialParameterMetadata& Metadata,
EMaterialSamplerType SamplerType
)

 Emits a material parameter value with given name, metadata and sampler type (if it is a texture) and returns it. Materials/MaterialIREmitter.h  
Emits the partial derivative of given value. Materials/MaterialIREmitter.h  

FValueRef Poison()

 Emits the poison value. Materials/MaterialIREmitter.h  

FValueRef Round ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef Saturate ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef Select ( FValueRef A,
FValueRef B,
FValueRef C
)

   Materials/MaterialIREmitter.h  
Emits an instruction that sets the material attribute with given property to given argument. Materials/MaterialIREmitter.h  

FValueRef Sin ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef Sinh ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef Smoothstep ( FValueRef A,
FValueRef B,
FValueRef C
)

   Materials/MaterialIREmitter.h  

FValueRef Sqrt ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef StageSwitch ( const FType* Type,
TConstArrayView< FValueRef > ValuePerStage
)

 Emits a stage switch instruction. Materials/MaterialIREmitter.h  

FValueRef Subscript ( FValueRef Value,
int32 Index
)

 Extracts the component with given index from the given argument value. Materials/MaterialIREmitter.h  

FValueRef Subtract ( FValueRef A,
FValueRef B
)

   Materials/MaterialIREmitter.h  
Swizzles the given argument by given mask. Materials/MaterialIREmitter.h  

FValueRef Tan ( FValueRef A
)

   Materials/MaterialIREmitter.h  

FValueRef TextureGather ( FValueRef Texture,
FValueRef TexCoord,
ETextureReadMode GatherMode,
ESamplerSourceMode SamplerSourceMode,
EMaterialSamplerType SamplerType
)

 Emits a texture gather instruction. Materials/MaterialIREmitter.h  

FValueRef TextureObject ( UTexture* Texture,
EMaterialSamplerType SamplerType
)

 Emits a texture object value of fiven sampler type and returns it. Materials/MaterialIREmitter.h  

FValueRef TextureSample ( FValueRef Texture,
FValueRef TexCoord,
bool bAddViewMaterialMipBias,
ESamplerSourceMode SamplerSourceMode,
EMaterialSamplerType SamplerType
)

 Emits a texture sample instruction. Materials/MaterialIREmitter.h  

FValueRef TextureSampleBias ( FValueRef Texture,
FValueRef TexCoord,
FValueRef MipBias,
bool bAddViewMaterialMipBias,
ESamplerSourceMode SamplerSourceMode,
EMaterialSamplerType SamplerType
)

 Emits a texture sample instruction with bias added to the automatically selected mip level. Materials/MaterialIREmitter.h  

FValueRef TextureSampleGrad ( FValueRef Texture,
FValueRef TexCoord,
FValueRef TexCoordDdx,
FValueRef TexCoordDdy,
bool bAddViewMaterialMipBias,
ESamplerSourceMode SamplerSourceMode,
EMaterialSamplerType SamplerType
)

 Emits a texture sample instruction using user provided partial derivatives. Materials/MaterialIREmitter.h  

FValueRef TextureSampleLevel ( FValueRef Texture,
FValueRef TexCoord,
FValueRef MipLevel,
bool bAddViewMaterialMipBias,
ESamplerSourceMode SamplerSourceMode,
EMaterialSamplerType SamplerType
)

 Emits a texture sample instruction with a manually given mip level. Materials/MaterialIREmitter.h  

bool ToConstantBool ( FValueRef Value
)

 Casts the value flowing into this input to a constant boolean and returns it. Materials/MaterialIREmitter.h  

FValueRef Truncate ( FValueRef A
)

   Materials/MaterialIREmitter.h  

const FType * TryGetCommonType ( const FType* A,
const FType* B
)

 Tries to find a common type between A and B. Materials/MaterialIREmitter.h  
Retrieves the value from the given input, if present. Materials/MaterialIREmitter.h  

FValueRef Vector2 ( FValueRef InX,
FValueRef InY
)

 Emits a 2D column vector dimensional value and returns it. Materials/MaterialIREmitter.h  

FValueRef Vector3 ( FValueRef InX,
FValueRef InY,
FValueRef InZ
)

 Emits a 3D column vector dimensional value and returns it. Materials/MaterialIREmitter.h  

FValueRef Vector4 ( FValueRef InX,
FValueRef InY,
FValueRef InZ,
FValueRef InW
)

 Emits a 4D column vector dimensional value and returns it. Materials/MaterialIREmitter.h  

Ask questions and help your peers Developer Forums

Write your own tutorials or read those from others Learning Library

On this page