ShaderVariantAssetBuilder: Provide registry property to disable (#5029)

The registry property name is:
"/O3DE/Atom/Shaders/BuildVariants"
Default value is <true>.

Signed-off-by: garrieta <garrieta@amazon.com>

Gems/Atom/Asset/Shader/Code/Source/Editor/AzslShaderBuilderSystemComponent.cpp

@@ -23,6 +23,7 @@
 
 #include <AzCore/Serialization/EditContext.h>
 #include <AzCore/Serialization/SerializeContext.h>
+#include <AzCore/Settings/SettingsRegistry.h>
 
 #include <CommonFiles/Preprocessor.h>
 #include <CommonFiles/GlobalBuildOptions.h>
@@ -91,6 +92,17 @@ namespace AZ
             m_shaderAssetBuilder.BusConnect(shaderAssetBuilderDescriptor.m_busId);
             AssetBuilderSDK::AssetBuilderBus::Broadcast(&AssetBuilderSDK::AssetBuilderBus::Handler::RegisterBuilderInformation, shaderAssetBuilderDescriptor);
 
+            // If, either the SettingsRegistry doesn't exist, or the property @EnableShaderVariantAssetBuilderRegistryKey is not found,
+            // the default is to enable the ShaderVariantAssetBuilder.
+            m_enableShaderVariantAssetBuilder = true;
+            auto settingsRegistry = AZ::SettingsRegistry::Get();
+            if (settingsRegistry)
+            {
+                settingsRegistry->Get(m_enableShaderVariantAssetBuilder, EnableShaderVariantAssetBuilderRegistryKey);
+            }
+
+            if (m_enableShaderVariantAssetBuilder)
+            {
                 // Register Shader Variant Asset Builder
                 AssetBuilderSDK::AssetBuilderDesc shaderVariantAssetBuilderDescriptor;
                 shaderVariantAssetBuilderDescriptor.m_name = "Shader Variant Asset Builder";
@@ -104,6 +116,7 @@ namespace AZ
 
                 m_shaderVariantAssetBuilder.BusConnect(shaderVariantAssetBuilderDescriptor.m_busId);
                 AssetBuilderSDK::AssetBuilderBus::Broadcast(&AssetBuilderSDK::AssetBuilderBus::Handler::RegisterBuilderInformation, shaderVariantAssetBuilderDescriptor);
+            }
 
             // Register Precompiled Shader Builder
             AssetBuilderSDK::AssetBuilderDesc precompiledShaderBuilderDescriptor;
@@ -121,7 +134,10 @@ namespace AZ
         void AzslShaderBuilderSystemComponent::Deactivate()
         {
             m_shaderAssetBuilder.BusDisconnect();
+            if (m_enableShaderVariantAssetBuilder)
+            {
                 m_shaderVariantAssetBuilder.BusDisconnect();
+            }
             m_precompiledShaderBuilder.BusDisconnect();
 
             RHI::ShaderPlatformInterfaceRegisterBus::Handler::BusDisconnect();

Gems/Atom/Asset/Shader/Code/Source/Editor/AzslShaderBuilderSystemComponent.h

@@ -61,7 +61,17 @@ namespace AZ
 
         private:
             ShaderAssetBuilder m_shaderAssetBuilder;
+
+            // The ShaderVariantAssetBuilder can be disabled with this registry key.
+            // By default it is enabled. A user might want to disable it when doing look development
+            // work with shaders or doing lots of iterative changes to shaders. In these cases
+            // GPU performance doesn't matter at all so it is important to not waste time
+            // building ShaderVariantAssets (Other than the Root ShaderVariantAsset, of course.).
+            static constexpr char EnableShaderVariantAssetBuilderRegistryKey[] = "/O3DE/Atom/Shaders/BuildVariants";
+            bool m_enableShaderVariantAssetBuilder = true;
+
             ShaderVariantAssetBuilder m_shaderVariantAssetBuilder;
+
             PrecompiledShaderBuilder m_precompiledShaderBuilder;
 
             /// Contains the ShaderPlatformInterface for all registered RHIs

Gems/Atom/Asset/Shader/Registry/atom_shaders.setreg

@@ -0,0 +1,10 @@
+{
+    "O3DE": {
+        "Atom": {
+            "Shaders": {
+                "BuildVariants": true
+                }
+            }
+        }
+    }
+}