Fix bug in ShaderVariantAssetBuilder. Add cvar in MeshDrawPacket class. (#61)

Fix bug in ShaderVariantAssetBuilder. Add a console variable to force root shader variant usage.

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

@@ -162,7 +162,7 @@ namespace AZ
             AZStd::string expectedHigherPrecedenceFileFullPath;
             AzFramework::StringFunc::Path::Join(gameProjectPath, RPI::ShaderVariantTreeAsset::CommonSubFolder, expectedHigherPrecedenceFileFullPath, false /* handle directory overlap? */, false /* be case insensitive? */);
             AzFramework::StringFunc::Path::Join(expectedHigherPrecedenceFileFullPath.c_str(), shaderProductFileRelativePath.c_str(), expectedHigherPrecedenceFileFullPath, false /* handle directory overlap? */, false /* be case insensitive? */);
-            AzFramework::StringFunc::Path::ReplaceExtension(expectedHigherPrecedenceFileFullPath, AZ::RPI::ShaderVariantAsset::Extension);
+            AzFramework::StringFunc::Path::ReplaceExtension(expectedHigherPrecedenceFileFullPath, AZ::RPI::ShaderVariantListSourceData::Extension);
             AzFramework::StringFunc::Path::Normalize(expectedHigherPrecedenceFileFullPath);
 
             AZStd::string normalizedShaderVariantListFileFullPath = shaderVariantListFileFullPath;

Gems/Atom/Feature/Common/Code/Include/Atom/Feature/Mesh/MeshFeatureProcessor.h

@@ -21,6 +21,7 @@
 #include <RayTracing/RayTracingFeatureProcessor.h>
 #include <AzCore/Asset/AssetCommon.h>
 #include <AtomCore/std/parallel/concurrency_checker.h>
+#include <AzCore/Console/Console.h>
 
 namespace AZ
 {
@@ -160,8 +161,14 @@ namespace AZ
 
             // called when reflection probes are modified in the editor so that meshes can re-evaluate their probes
             void UpdateMeshReflectionProbes();
-
         private:
+            void ForceRebuildDrawPackets(const AZ::ConsoleCommandContainer& arguments);
+            AZ_CONSOLEFUNC(MeshFeatureProcessor,
+                ForceRebuildDrawPackets,
+                AZ::ConsoleFunctorFlags::Null,
+                "(For Testing) Invalidates all mesh draw packets, causing them to rebuild on the next frame."
+            );
+
             MeshFeatureProcessor(const MeshFeatureProcessor&) = delete;
 
             // RPI::SceneNotificationBus::Handler overrides...

Gems/Atom/Feature/Common/Code/Source/Mesh/MeshFeatureProcessor.cpp

@@ -387,6 +387,11 @@ namespace AZ
             }
         }
 
+        void MeshFeatureProcessor::ForceRebuildDrawPackets([[maybe_unused]] const AZ::ConsoleCommandContainer& arguments)
+        {
+            m_forceRebuildDrawPackets = true;
+        }
+
         void MeshFeatureProcessor::OnRenderPipelineAdded(RPI::RenderPipelinePtr pipeline)
         {
             m_forceRebuildDrawPackets = true;;

Gems/Atom/RPI/Code/Source/RPI.Public/MeshDrawPacket.cpp

@@ -17,11 +17,20 @@
 #include <Atom/RPI.Public/Scene.h> 
 #include <Atom/RPI.Reflect/Material/MaterialFunctor.h>
 #include <Atom/RHI/DrawPacketBuilder.h>
+#include <AzCore/Console/Console.h>
 
 namespace AZ
 {   
     namespace RPI
     {
+        AZ_CVAR(bool,
+            r_forceRootShaderVariantUsage,
+            false,
+            [](const bool&) { AZ::Interface<AZ::IConsole>::Get()->PerformCommand("MeshFeatureProcessor.ForceRebuildDrawPackets"); },
+            ConsoleFunctorFlags::Null,
+            "(For Testing) Forces usage of root shader variant in the mesh draw packet level, ignoring any other shader variants that may exist."
+        );
+
         MeshDrawPacket::MeshDrawPacket(
             ModelLod& modelLod,
             size_t modelLodMeshIndex,
@@ -187,7 +196,7 @@ namespace AZ
                 }
 
                 const ShaderVariantId finalVariantId = shaderOptions.GetShaderVariantId();
-                const ShaderVariant& variant = shader->GetVariant(finalVariantId);
+                const ShaderVariant& variant = r_forceRootShaderVariantUsage ? shader->GetRootVariant() : shader->GetVariant(finalVariantId);
 
                 Data::Instance<ShaderResourceGroup> drawSrg;
                 if (drawSrgAsset)