VertexDescriptionInputs BuildVertexDescriptionInputs(Attributes input)
{
    VertexDescriptionInputs output;
    ZERO_INITIALIZE(VertexDescriptionInputs, output);

    $VertexDescriptionInputs.ObjectSpaceNormal:                         output.ObjectSpaceNormal =                          input.normalOS;
    $VertexDescriptionInputs.WorldSpaceNormal:                          output.WorldSpaceNormal =                           TransformObjectToWorldNormal(input.normalOS);
    $VertexDescriptionInputs.ViewSpaceNormal:                           output.ViewSpaceNormal =                            TransformWorldToViewDir(output.WorldSpaceNormal);
    $VertexDescriptionInputs.TangentSpaceNormal:                        output.TangentSpaceNormal =                         float3(0.0f, 0.0f, 1.0f);
    $VertexDescriptionInputs.ObjectSpaceTangent:                        output.ObjectSpaceTangent =                         input.tangentOS.xyz;
    $VertexDescriptionInputs.WorldSpaceTangent:                         output.WorldSpaceTangent =                          TransformObjectToWorldDir(input.tangentOS.xyz);
    $VertexDescriptionInputs.ViewSpaceTangent:                          output.ViewSpaceTangent =                           TransformWorldToViewDir(output.WorldSpaceTangent);
    $VertexDescriptionInputs.TangentSpaceTangent:                       output.TangentSpaceTangent =                        float3(1.0f, 0.0f, 0.0f);
    $VertexDescriptionInputs.ObjectSpaceBiTangent:                      output.ObjectSpaceBiTangent =                       normalize(cross(input.normalOS, input.tangentOS.xyz) * (input.tangentOS.w > 0.0f ? 1.0f : -1.0f) * GetOddNegativeScale());
    $VertexDescriptionInputs.WorldSpaceBiTangent:                       output.WorldSpaceBiTangent =                        TransformObjectToWorldDir(output.ObjectSpaceBiTangent);
    $VertexDescriptionInputs.ViewSpaceBiTangent:                        output.ViewSpaceBiTangent =                         TransformWorldToViewDir(output.WorldSpaceBiTangent);
    $VertexDescriptionInputs.TangentSpaceBiTangent:                     output.TangentSpaceBiTangent =                      float3(0.0f, 1.0f, 0.0f);
    $VertexDescriptionInputs.ObjectSpacePosition:                       output.ObjectSpacePosition =                        input.positionOS;
    $VertexDescriptionInputs.WorldSpacePosition:                        output.WorldSpacePosition =                         TransformObjectToWorld(input.positionOS);
    $VertexDescriptionInputs.ViewSpacePosition:                         output.ViewSpacePosition =                          TransformWorldToView(output.WorldSpacePosition);
    $VertexDescriptionInputs.TangentSpacePosition:                      output.TangentSpacePosition =                       float3(0.0f, 0.0f, 0.0f);
    $VertexDescriptionInputs.AbsoluteWorldSpacePosition:                output.AbsoluteWorldSpacePosition =                 GetAbsolutePositionWS(TransformObjectToWorld(input.positionOS));
    $VertexDescriptionInputs.ObjectSpacePositionPredisplacement:        output.ObjectSpacePositionPredisplacement =         input.positionOS;
    $VertexDescriptionInputs.WorldSpacePositionPredisplacement:         output.WorldSpacePositionPredisplacement =          TransformObjectToWorld(input.positionOS);
    $VertexDescriptionInputs.ViewSpacePositionPredisplacement:          output.ViewSpacePositionPredisplacement =           TransformWorldToView(output.WorldSpacePosition);
    $VertexDescriptionInputs.TangentSpacePositionPredisplacement:       output.TangentSpacePositionPredisplacement =        float3(0.0f, 0.0f, 0.0f);
    $VertexDescriptionInputs.AbsoluteWorldSpacePositionPredisplacement: output.AbsoluteWorldSpacePositionPredisplacement =  GetAbsolutePositionWS(TransformObjectToWorld(input.positionOS));
    $VertexDescriptionInputs.WorldSpaceViewDirection:                   output.WorldSpaceViewDirection =                    GetWorldSpaceNormalizeViewDir(output.WorldSpacePosition);
    $VertexDescriptionInputs.ObjectSpaceViewDirection:                  output.ObjectSpaceViewDirection =                   TransformWorldToObjectDir(output.WorldSpaceViewDirection);
    $VertexDescriptionInputs.ViewSpaceViewDirection:                    output.ViewSpaceViewDirection =                     TransformWorldToViewDir(output.WorldSpaceViewDirection);
    $VertexDescriptionInputs.TangentSpaceViewDirection:                 float3x3 tangentSpaceTransform =                    float3x3(output.WorldSpaceTangent,output.WorldSpaceBiTangent,output.WorldSpaceNormal);
    $VertexDescriptionInputs.TangentSpaceViewDirection:                 output.TangentSpaceViewDirection =                  TransformWorldToTangent(output.WorldSpaceViewDirection, tangentSpaceTransform);
    $VertexDescriptionInputs.ScreenPosition:                            output.ScreenPosition =                             ComputeScreenPos(TransformWorldToHClip(output.WorldSpacePosition), _ProjectionParams.x);
    $VertexDescriptionInputs.NDCPosition:                               output.NDCPosition =                                output.ScreenPosition.xy / output.ScreenPosition.w;
    $VertexDescriptionInputs.PixelPosition:                             output.PixelPosition =                              float2(output.NDCPosition.x, 1.0f - output.NDCPosition.y) * _ScreenParams.xy;
    $VertexDescriptionInputs.uv0:                                       output.uv0 =                                        input.uv0;
    $VertexDescriptionInputs.uv1:                                       output.uv1 =                                        input.uv1;
    $VertexDescriptionInputs.uv2:                                       output.uv2 =                                        input.uv2;
    $VertexDescriptionInputs.uv3:                                       output.uv3 =                                        input.uv3;
    $VertexDescriptionInputs.VertexColor:                               output.VertexColor =                                input.color;
    $VertexDescriptionInputs.TimeParameters:                            output.TimeParameters =                             _TimeParameters.xyz;
    $VertexDescriptionInputs.BoneWeights:                               output.BoneWeights =                                input.weights;
    $VertexDescriptionInputs.BoneIndices:                               output.BoneIndices =                                input.indices;
    $VertexDescriptionInputs.VertexID:                                  output.VertexID =                                   input.vertexID;

    return output;
}

void TerrainVaryingGeneration(inout Attributes input, inout Varyings output)
{
    float4 positionOS = float4(input.positionOS, 1.0);
    #if defined(VARYINGS_NEED_TEXCOORD0) && defined(ATTRIBUTES_NEED_NORMAL)
        TerrainInstancing(positionOS, input.normalOS, input.uv0.xy);
    #elif defined(VARYINGS_NEED_TEXCOORD0)
        float3 normal = float3(0, 0, 0);
        TerrainInstancing(positionOS, normal, input.uv0.xy);
    #elif defined(ATTRIBUTES_NEED_NORMAL)
        TerrainInstancing(positionOS, input.normalOS);
    #else
        TerrainInstancing(positionOS);
    #endif
    input.positionOS = positionOS.xyz;

#if defined(VARYINGS_NEED_TEXCOORD0) && defined(UNIVERSAL_TERRAIN_SPLAT01)
    output.uvSplat01.xy = TRANSFORM_TEX(input.uv0, _Splat0);
    output.uvSplat01.zw = TRANSFORM_TEX(input.uv0, _Splat1);
#endif
#if defined(VARYINGS_NEED_TEXCOORD0) && defined(UNIVERSAL_TERRAIN_SPLAT23)
    output.uvSplat23.xy = TRANSFORM_TEX(input.uv0, _Splat2);
    output.uvSplat23.zw = TRANSFORM_TEX(input.uv0, _Splat3);
#endif
}

float4 ConstructTerrainTangent(float3 normal, float3 positiveZ)
{
    // Consider a flat terrain. It should have tangent be (1, 0, 0) and bitangent be (0, 0, 1) as the UV of the terrain grid mesh is a scale of the world XZ position.
    // In CreateTangentToWorld function (in SpaceTransform.hlsl), it is cross(normal, tangent) * sgn for the bitangent vector.
    // It is not true in a left-handed coordinate system for the terrain bitangent, if we provide 1 as the tangent.w. It would produce (0, 0, -1) instead of (0, 0, 1).
    // Also terrain's tangent calculation was wrong in a left handed system because cross((0,0,1), terrainNormalOS) points to the wrong direction as negative X.
    // Therefore all the 4 xyzw components of the tangent needs to be flipped to correct the tangent frame.
    // (See TerrainLitData.hlsl - GetSurfaceAndBuiltinData)
    float3 tangent = cross(normal, positiveZ);
    return float4(tangent, -1);
}