API Direct3D 12 de Variable Rate Shading

enum D3D12_SHADING_RATE_TIER
{
    D3D12_SHADING_RATE_TIER_NOT_SUPPORTED,
    D3D12_SHADING_RATE_TIER_1,
    D3D12_SHADING_RATE_TIER_2,
};

struct D3D12_FEATURE_DATA_D3D12_OPTIONS6
{
    BOOL AdditionalShadingRatesSupported; 
    BOOL PerPrimitiveShadingRateIndependentOfViewportUse;
    D3D12_SHADING_RATE_TIER ShadingRateTier;
    UINT ShadingRateImageTileSize;
};

enum D3D12_FEATURE
{
    // ...
    D3D12_FEATURE_D3D12_OPTIONS6
};

// Check that Tier 1 is supported.
D3D12_FEATURE_DATA_D3D12_OPTIONS6 options;
return 
    SUCCEEDED(m_device->CheckFeatureSupport(
        D3D12_FEATURE_D3D12_OPTIONS6, 
        &options, 
        sizeof(options))) && 
    options.ShadingRateTier == D3D12_SHADING_RATE_TIER_1;

enum D3D12_SHADING_RATE
{
    D3D12_SHADING_RATE_1X1 = 0x0, // No change to shading rate.
    D3D12_SHADING_RATE_1X2 = 0x1, // Reduces vertical resolution 2x.
    D3D12_SHADING_RATE_2X1 = 0x4, // Reduces horizontal resolution 2x.
    D3D12_SHADING_RATE_2X2 = 0x5, // Reduces both axes by 2x.
    D3D12_SHADING_RATE_2X4 = 0x6, // Reduce horizontal resolution 2x, vertical by 4x.
    D3D12_SHADING_RATE_4X2 = 0x9, // Reduce horizontal resolution 4x, vertical by 2x.
    D3D12_SHADING_RATE_4X4 = 0xA, // Reduces both axes by 4x.
};

enum D3D12_AXIS_SHADING_RATE
{
    D3D12_AXIS_SHADING_RATE_1X = 0x0,
    D3D12_AXIS_SHADING_RATE_2X = 0x1, 
    D3D12_AXIS_SHADING_RATE_4X = 0x2
};

#define D3D12_MAKE_COARSE_SHADING_RATE(x,y) ((x) << 2 | (y))
D3D12_MAKE_COARSE_SHADING_RATE(
    D3D12_AXIS_SHADING_RATE_2X, 
    D3D12_AXIS_SHADING_RATE_1X)

#define D3D12_GET_COARSE_SHADING_RATE_X_AXIS(x) ((x) >> 2 )
#define D3D12_GET_COARSE_SHADING_RATE_Y_AXIS(y) ((y) & 3 )

enum D3D12_SHADING_RATE_COMBINER
{
    D3D12_SHADING_RATE_COMBINER_PASSTHROUGH,
    D3D12_SHADING_RATE_COMBINER_OVERRIDE,
    D3D12_SHADING_RATE_COMBINER_MIN,
    D3D12_SHADING_RATE_COMBINER_MAX,
    D3D12_SHADING_RATE_COMBINER_SUM,
};

class ID3D12GraphicsCommandList5: public ID3D12GraphicsCommandList4
{
public:
    // ...
    virtual void RSSetShadingRate(
        D3D12_SHADING_RATE baseShadingRate, 
        _In_reads_opt_(2) D3D12_SHADING_RATE_COMBINER* combiners) = 0;
};

enum D3D12_RESOURCE_STATES
{
    // ...
    D3D12_RESOURCE_STATE_SHADING_RATE_SOURCE
};

class ID3D12GraphicsCommandList3: public ID3D12GraphicsCommandList2
{
public:
    // ...
    virtual void RSSetShadingRateImage(ID3D12Resource* image) = 0;
};

m_commandList->RSSetShadingRateImage(screenSpaceImage);

D3D12_FEATURE_DATA_D3D12_OPTIONS6 options;
return 
    SUCCEEDED(m_device->CheckFeatureSupport(
        D3D12_FEATURE_D3D12_OPTIONS6, 
        &options, 
        sizeof(options))) && 
    UINT tileSize = options.ShadingRateImageTileSize;