Add precise keyword to the depth and forward pass shaders. (#6536)

* Add precise keyword to the depth and forward pass shaders. Make sure metal shader pipeline passes the invariant along

Signed-off-by: rgba16f <82187279+rgba16f@users.noreply.github.com>

* Update with VickyAtAZ's feedback, split the preserve invariance into a separate string

Signed-off-by: rgba16f <82187279+rgba16f@users.noreply.github.com>

* Fix attribute comment alignment in the shaders

Signed-off-by: rgba16f <82187279+rgba16f@users.noreply.github.com>

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

@@ -82,8 +82,7 @@ namespace AZ
             // Register Shader Asset Builder
             AssetBuilderSDK::AssetBuilderDesc shaderAssetBuilderDescriptor;
             shaderAssetBuilderDescriptor.m_name = "Shader Asset Builder";
-            shaderAssetBuilderDescriptor.m_version = 108; // The Build Time Stamp of ShaderAsset And ShaderVariantAsset Should Be Based On GetTimeUTCMilliSecond()
-            // .shader file changes trigger rebuilds
+            shaderAssetBuilderDescriptor.m_version = 109; // Modify Metal shader platform to permit the precise keyword to fix depth bitwise mismatch between passes
             shaderAssetBuilderDescriptor.m_patterns.push_back(AssetBuilderSDK::AssetBuilderPattern( AZStd::string::format("*.%s", RPI::ShaderSourceData::Extension), AssetBuilderSDK::AssetBuilderPattern::PatternType::Wildcard));
             shaderAssetBuilderDescriptor.m_busId = azrtti_typeid<ShaderAssetBuilder>();
             shaderAssetBuilderDescriptor.m_createJobFunction = AZStd::bind(&ShaderAssetBuilder::CreateJobs, &m_shaderAssetBuilder, AZStd::placeholders::_1, AZStd::placeholders::_2);

Gems/Atom/Feature/Common/Assets/Materials/Types/StandardPBR_DepthPass_WithPS.azsl

@@ -29,7 +29,7 @@ struct VSInput
 struct VSDepthOutput
 {
     // "centroid" is needed for SV_Depth to compile
-    linear centroid float4 m_position : SV_Position;
+    precise linear centroid float4 m_position : SV_Position;
     float2 m_uv[UvSetCount] : UV1;
 
     // only used for parallax depth calculation

Gems/Atom/Feature/Common/Assets/Materials/Types/StandardPBR_ForwardPass.azsl

@@ -62,7 +62,7 @@ struct VSOutput
 {
     // Base fields (required by the template azsli file)...
     // "centroid" is needed for SV_Depth to compile
-    linear centroid float4 m_position : SV_Position;
+    precise linear centroid float4 m_position : SV_Position;
     float3 m_normal: NORMAL;
     float3 m_tangent : TANGENT; 
     float3 m_bitangent : BITANGENT; 

Gems/Atom/Feature/Common/Assets/ShaderLib/Atom/Features/PBR/Surfaces/BasePbrSurfaceData.azsli

@@ -24,7 +24,7 @@ static const float MinRoughnessA = 0.0005f;
 
 class BasePbrSurfaceData
 {
-    float3 position;            //!< Position in world-space
+    precise float3 position;    //!< Position in world-space
     float3 normal;              //!< Normal in world-space
     float3 albedo;              //!< Albedo color of the non-metallic material, will be multiplied against the diffuse lighting value
     float3 specularF0;          //!< Fresnel f0 spectral value of the surface

Gems/Atom/Feature/Common/Assets/ShaderLib/Atom/Features/PBR/Surfaces/StandardSurface.azsli

@@ -20,7 +20,7 @@ class Surface
 
     // ------- BasePbrSurfaceData -------
     
-    float3 position;            //!< Position in world-space
+    precise float3 position;    //!< Position in world-space
     float3 normal;              //!< Normal in world-space
     float3 vertexNormal;        //!< Vertex normal in world-space
     float3 albedo;              //!< Albedo color of the non-metallic material, will be multiplied against the diffuse lighting value

Gems/Atom/RHI/Metal/Code/Source/RHI.Builders/ShaderPlatformInterface.cpp

@@ -347,7 +347,7 @@ namespace AZ
             // spirv cross compiler executable
             static const char* spirvCrossRelativePath = "Builders/SPIRVCross/spirv-cross";
            
-            AZStd::string spirvCrossCommandOptions = AZStd::string::format("--msl --msl-version 20100 --msl-argument-buffers --msl-decoration-binding --msl-texture-buffer-native --output \"%s\" \"%s\"", shaderMSLOutputFile.c_str(), shaderSpirvOutputFile.c_str());
+            AZStd::string spirvCrossCommandOptions = AZStd::string::format("--msl --msl-version 20100 --msl-invariant-float-math --msl-argument-buffers --msl-decoration-binding --msl-texture-buffer-native --output \"%s\" \"%s\"", shaderMSLOutputFile.c_str(), shaderSpirvOutputFile.c_str());
             
             // Run spirv cross
             if (!RHI::ExecuteShaderCompiler(spirvCrossRelativePath, spirvCrossCommandOptions, shaderSpirvOutputFile, "SpirvCross"))
@@ -426,6 +426,8 @@ namespace AZ
             //Debug symbols are always enabled at the moment. Need to turn them off for optimized shader assets. 
             AZStd::string shaderDebugInfo = "-gline-tables-only -MO";
 
+            AZStd::string shaderMslToAirOptions = "-fpreserve-invariance";
+
             //Apply the correct platform sdk option
             AZStd::string platformSdk = "macosx";
             if (platform.HasTag("mobile"))
@@ -434,7 +436,7 @@ namespace AZ
             }
             
             //Convert to air file
-            AZStd::string mslToAirCommandOptions = AZStd::string::format("-sdk %s metal \"%s\" %s -c -o \"%s\"", platformSdk.c_str(), inputMetalFile.c_str(), shaderDebugInfo.c_str(), outputAirFile.c_str());
+            AZStd::string mslToAirCommandOptions = AZStd::string::format("-sdk %s metal \"%s\" %s %s -c -o \"%s\"", platformSdk.c_str(), inputMetalFile.c_str(), shaderDebugInfo.c_str(), shaderMslToAirOptions.c_str(), outputAirFile.c_str());
             
             if (!RHI::ExecuteShaderCompiler("/usr/bin/xcrun", mslToAirCommandOptions, inputMetalFile, "MslToAir"))
             {