bIsSPIRV

bIsSPIRV

#Overview

name: bIsSPIRV

The value of this variable can be defined or overridden in .ini config files. 4 .ini config files referencing this setting variable.

It is referenced in 3 C++ source files.

#Summary

#Usage in the C++ source code

The purpose of bIsSPIRV is to indicate whether a specific shader platform supports or uses SPIR-V (Standard Portable Intermediate Representation - Vulkan) as its shader intermediate language.

This setting variable is primarily used in the rendering system of Unreal Engine 5, specifically within the RHI (Rendering Hardware Interface) module. It’s part of the data-driven shader platform information system, which allows for flexible configuration of shader compilation and execution across different graphics APIs and hardware platforms.

The value of this variable is set during the parsing of data-driven shader information, as seen in the ParseDataDrivenShaderInfo function in the DataDrivenShaderPlatformInfo.cpp file. It’s stored as a bit field within the FGenericDataDrivenShaderPlatformInfo class.

bIsSPIRV interacts with other shader platform configuration variables, such as bIsHlslcc, bSupportsDxc, and bSupportsVariableRateShading. These variables collectively define the capabilities and characteristics of a specific shader platform.

Developers must be aware that this variable affects how shaders are compiled and processed for different graphics APIs. When bIsSPIRV is true, it indicates that the shader code should be compiled to or is expected to be in SPIR-V format, which is primarily used with Vulkan but can also be used with other APIs that support it.

Best practices when using this variable include:

1. Ensure that the correct value is set for each supported platform to avoid shader compilation issues.
2. Consider the implications of SPIR-V support when writing cross-platform shader code.
3. Use the provided accessor method GetIsSPIRV to check for SPIR-V support rather than accessing the variable directly.
4. Be aware of the potential performance implications and API requirements when SPIR-V is used.
5. Coordinate with the graphics programming team to ensure that the shader compilation pipeline is correctly configured for SPIR-V when this flag is set.

#Setting Variables

#References In INI files

Location: <Workspace>/Engine/Config/Mac/DataDrivenPlatformInfo.ini:46, section: [ShaderPlatform METAL_SM5]

• INI Section: ShaderPlatform METAL_SM5
• Raw value: true
• Is Array: False

Location: <Workspace>/Engine/Config/Mac/DataDrivenPlatformInfo.ini:86, section: [ShaderPlatform METAL_SM6]

• INI Section: ShaderPlatform METAL_SM6
• Raw value: true
• Is Array: False

Location: <Workspace>/Engine/Config/VulkanPC/DataDrivenPlatformInfo.ini:22, section: [ShaderPlatform VULKAN_SM5]

• INI Section: ShaderPlatform VULKAN_SM5
• Raw value: true
• Is Array: False

Location: <Workspace>/Engine/Config/VulkanPC/DataDrivenPlatformInfo.ini:153, section: [ShaderPlatform VULKAN_SM6]

• INI Section: ShaderPlatform VULKAN_SM6
• Raw value: true
• Is Array: False

#References in C++ code

#Callsites

This variable is referenced in the following C++ source code:

#Loc: <Workspace>/Engine/Source/Runtime/RHI/Private/DataDrivenShaderPlatformInfo.cpp:264

Scope (from outer to inner):

file
function     void FGenericDataDrivenShaderPlatformInfo::ParseDataDrivenShaderInfo

Source code excerpt:

	GET_SECTION_BOOL_HELPER(bSupportsDxc);
	GET_SECTION_BOOL_HELPER(bSupportsVariableRateShading);
	GET_SECTION_BOOL_HELPER(bIsSPIRV);
	GET_SECTION_INT_HELPER(NumberOfComputeThreads);

	GET_SECTION_BOOL_HELPER(bWaterUsesSimpleForwardShading);
	GET_SECTION_BOOL_HELPER(bSupportsHairStrandGeometry);
	GET_SECTION_BOOL_HELPER(bSupportsDOFHybridScattering);
	GET_SECTION_BOOL_HELPER(bNeedsExtraMobileFrames);

#Loc: <Workspace>/Engine/Source/Runtime/RHI/Public/DataDrivenShaderPlatformInfo.h:87

Scope (from outer to inner):

file
class        class FGenericDataDrivenShaderPlatformInfo

Source code excerpt:

	uint32 bIsHlslcc : 1;
	uint32 bSupportsDxc : 1; // Whether DirectXShaderCompiler (DXC) is supported
	uint32 bIsSPIRV : 1;
	uint32 bSupportsVariableRateShading : 1;
	uint32 NumberOfComputeThreads : 10;
	uint32 bWaterUsesSimpleForwardShading : 1;
	uint32 bSupportsHairStrandGeometry : 1;
	uint32 bSupportsDOFHybridScattering : 1;
	uint32 bNeedsExtraMobileFrames : 1;

#Loc: <Workspace>/Engine/Source/Runtime/RHI/Public/DataDrivenShaderPlatformInfo.h:605

Scope (from outer to inner):

file
class        class FGenericDataDrivenShaderPlatformInfo
function     static const bool GetIsSPIRV

Source code excerpt:

	{
		check(IsValid(Platform));
		return Infos[Platform].bIsSPIRV;
	}

	static FORCEINLINE_DEBUGGABLE const bool GetSupportsVariableRateShading(const FStaticShaderPlatform Platform)
	{
		check(IsValid(Platform));
		return Infos[Platform].bSupportsVariableRateShading;