HDRenderPipeline: Add support for BC5 normal map

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Editor/LitUI.cs

             public static GUIContent maskMapSText = new GUIContent("Mask Map - M(R), AO(G), S(A)", "Mask map");
 
             public static GUIContent normalMapSpaceText = new GUIContent("Normal/Tangent Map space", "");
-            public static GUIContent normalMapText = new GUIContent("Normal Map", "Normal Map (DXT5) - Need to implement BC5");
             public static GUIContent specularOcclusionMapText = new GUIContent("Specular Occlusion Map (RGBA)", "Specular Occlusion Map");
             public static GUIContent horizonFadeText = new GUIContent("Horizon Fade (Spec occlusion)", "horizon fade is use to control specular occlusion");
 

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitDataInternal.hlsl

 #endif
     surfaceData.normalWS = float3(0.0, 0.0, 0.0); // Need to init this to keep quiet the compiler, but this is overriden later (0, 0, 0) so if we forget to override the compiler may comply.
 
-    // TODO: think about using BC5
     normalTS = ADD_IDX(GetNormalTS)(input, layerTexCoord, detailNormalTS, detailMask, false, 0.0);
 
 #if defined(_MASKMAP_IDX)
 
     surfaceData.materialId = (_EnableSSS || _MaterialID != MATERIALID_LIT_SSS) ? _MaterialID : MATERIALID_LIT_STANDARD;
 
-    // TODO: think about using BC5
 #ifdef _TANGENTMAP
     #ifdef _NORMALMAP_TANGENT_SPACE_IDX // Normal and tangent use same space
     float3 tangentTS = SAMPLE_UVMAPPING_NORMALMAP(_TangentMap, sampler_TangentMap, layerTexCoord.base, 1.0);

Assets/ScriptableRenderPipeline/ShaderLibrary/NormalSurfaceGradient.hlsl

     return deriv * scale;
 }
 
+// Unpack normal as DXT5nm (1, y, 0, x) or BC5 (x, y, 0, 1)
+float2 UnpackDerivativeNormalRGorAG(float4 packedNormal, float scale = 1.0)
+{
+    // This do the trick
+    packedNormal.w *= packedNormal.x;
+    return UnpackDerivativeNormalAG(packedNormal, scale);
+}
+
 float2 UnpackDerivativeNormalRGB(float4 packedNormal, float scale = 1.0)
 {
     const float fS = 1.0 / (128.0 * 128.0);

Assets/ScriptableRenderPipeline/ShaderLibrary/Packing.hlsl

 float3 UnpackNormalmapRGorAG(float4 packedNormal, float scale = 1.0)
 {
     // This do the trick
-    packedNormal.x *= packedNormal.w;
-
-    float3 normal;
-    normal.xy = packedNormal.xy * 2.0 - 1.0;
-    normal.xy *= scale;
-    normal.z = sqrt(1.0 - saturate(dot(normal.xy, normal.xy)));
-    return normal;
+    packedNormal.w *= packedNormal.x;
+    return UnpackNormalAG(packedNormal, scale);
 }
 
 //-----------------------------------------------------------------------------

Assets/ScriptableRenderPipeline/ShaderLibrary/SampleUVMappingInternal.hlsl

 
 // Nested multiple includes of the file to handle all variations of normal map (AG, RG or RGB)
 
-// TODO: Handle BC5 format, currently this code is for DXT5nm - After the change, rename this function UnpackNormalmapRGorAG
-// This version is use for the base normal map
+// This version is use for the base normal map (BC5 or DXT5nm)
-#define UNPACK_NORMAL_FUNC UnpackNormalAG
-#define UNPACK_DERIVATIVE_FUNC UnpackDerivativeNormalAG
+#define UNPACK_NORMAL_FUNC UnpackNormalmapRGorAG
+#define UNPACK_DERIVATIVE_FUNC UnpackDerivativeNormalRGorAG
 #endif
 #include "SampleUVMappingNormalInternal.hlsl"
 #undef ADD_NORMAL_FUNC_SUFFIX
-// This version is for normalmap with AG encoding only. Mainly use with details map.
+// This version is for normalmap with AG encoding only. Use with details map encoded with others properties (like smoothness).
-#if defined(UNITY_NO_DXT5nm)
-#define UNPACK_NORMAL_FUNC UnpackNormalRGB
-#define UNPACK_DERIVATIVE_FUNC UnpackDerivativeNormalRGB
-#else
-#endif
 #include "SampleUVMappingNormalInternal.hlsl"
 #undef ADD_NORMAL_FUNC_SUFFIX
 #undef UNPACK_NORMAL_FUNC