r.Material.RoughDiffuse

r.Material.RoughDiffuse

#Overview

name: r.Material.RoughDiffuse

This variable is created as a Console Variable (cvar).

• type: Var
• help: Enable rough diffuse material.

It is referenced in 3 C++ source files.

#Summary

#Usage in the C++ source code

The purpose of r.Material.RoughDiffuse is to enable rough diffuse material in Unreal Engine’s rendering system. This setting variable controls whether the engine should use a more physically accurate model for diffuse lighting that takes surface roughness into account.

Key points about r.Material.RoughDiffuse:

1. It is part of the material and lighting subsystem in Unreal Engine.

2. The value is set through a console variable (CVar), allowing runtime modification.

3. It affects shader compilation, as evidenced by its use in shader key generation (ShaderMapAppendKeyString function).

4. When enabled, it adds the “_MATRDIFF” suffix to the shader key string, likely triggering the compilation of shader variants that include rough diffuse calculations.

5. In the shader code, it sets the MATERIAL_ROUGHDIFFUSE define, but only if Substrate (a newer material system) is not enabled or if Substrate’s own rough diffuse setting is disabled.

6. The variable interacts with the Substrate system, showing a transition between older and newer rendering techniques.

Developers should be aware that:

1. Enabling this feature may increase rendering cost but provide more accurate lighting results.
2. It may not have an effect if the Substrate system is enabled and configured differently.
3. Changing this setting at runtime will likely require shader recompilation, which could cause a performance hitch.

Best practices:

1. Consider the performance implications before enabling this feature, especially on lower-end hardware.
2. Test the visual impact in various lighting conditions to determine if the quality improvement justifies the performance cost.
3. If using the Substrate system, be aware of how it interacts with this setting to avoid conflicts or unexpected behavior.
4. When making changes to this setting, plan for potential shader recompilation time, especially in development builds.

#References in C++ code

#Callsites

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

#Loc: <Workspace>/Engine/Source/Runtime/RenderCore/Private/RenderUtils.cpp:1783

Scope: file

Source code excerpt:

// Transition render settings that will disappear when Substrate gets enabled
static TAutoConsoleVariable<int32> CVarMaterialRoughDiffuse(
	TEXT("r.Material.RoughDiffuse"),
	0,
	TEXT("Enable rough diffuse material."),
	ECVF_ReadOnly | ECVF_RenderThreadSafe);

static TAutoConsoleVariable<int32> CVarSubstrateRoughDiffuse(
	TEXT("r.Substrate.RoughDiffuse"),

#Loc: <Workspace>/Engine/Source/Runtime/Engine/Private/ShaderCompiler/ShaderCompiler.cpp:8552

Scope (from outer to inner):

file
function     void GlobalBeginCompileShader

Source code excerpt:

	{
		static IConsoleVariable* CVar = IConsoleManager::Get().FindConsoleVariable(TEXT("r.Material.RoughDiffuse"));
		const bool bMaterialRoughDiffuse = CVar && CVar->GetInt() != 0;
		const bool bSubstrateRoughDiffuse = Substrate::IsRoughDiffuseEnabled() && !Substrate::IsBackCompatibilityEnabled();
		SET_SHADER_DEFINE(Input.Environment, MATERIAL_ROUGHDIFFUSE, (bSubstrate ? bSubstrateRoughDiffuse : bMaterialRoughDiffuse) ? 1 : 0);
	}

	{

#Loc: <Workspace>/Engine/Source/Runtime/RenderCore/Private/Shader.cpp:2099

Scope (from outer to inner):

file
function     void ShaderMapAppendKeyString

Source code excerpt:

	{
		static const auto CVar = IConsoleManager::Get().FindTConsoleVariableDataInt(TEXT("r.Material.RoughDiffuse"));
		if (CVar && CVar->GetValueOnAnyThread() > 0)
		{
			KeyString += FString::Printf(TEXT("_MATRDIFF"));
		}
	}