Vulkan® 1.2.148 - A Specification (with all registered extensions)

28. The Framebuffer

28.1. Blending

Blending combines the incoming source fragment’s R, G, B, and A values with the destination R, G, B, and A values of each sample stored in the framebuffer at the fragment’s (x_f,y_f) location. Blending is performed for each color sample covered by the fragment, rather than just once for each fragment.

Source and destination values are combined according to the blend operation, quadruplets of source and destination weighting factors determined by the blend factors, and a blend constant, to obtain a new set of R, G, B, and A values, as described below.

Blending is computed and applied separately to each color attachment used by the subpass, with separate controls for each attachment.

Prior to performing the blend operation, signed and unsigned normalized fixed-point color components undergo an implied conversion to floating-point as specified by Conversion from Normalized Fixed-Point to Floating-Point. Blending computations are treated as if carried out in floating-point, and basic blend operations are performed with a precision and dynamic range no lower than that used to represent destination components. Advanced blending operations are performed with a precision and dynamic range no lower than the smaller of that used to represent destination components or that used to represent 16-bit floating-point values.

Note

Blending is only defined for floating-point, UNORM, SNORM, and sRGB formats. Within those formats, the implementation may only support blending on some subset of them. Which formats support blending is indicated by VK_FORMAT_FEATURE_COLOR_ATTACHMENT_BLEND_BIT.

The pipeline blend state is included in the VkPipelineColorBlendStateCreateInfo structure during graphics pipeline creation:

The VkPipelineColorBlendStateCreateInfo structure is defined as:

// Provided by VK_VERSION_1_0
typedef struct VkPipelineColorBlendStateCreateInfo {
    VkStructureType                               sType;
    const void*                                   pNext;
    VkPipelineColorBlendStateCreateFlags          flags;
    VkBool32                                      logicOpEnable;
    VkLogicOp                                     logicOp;
    uint32_t                                      attachmentCount;
    const VkPipelineColorBlendAttachmentState*    pAttachments;
    float                                         blendConstants[4];
} VkPipelineColorBlendStateCreateInfo;

sType is the type of this structure.
pNext is NULL or a pointer to a structure extending this structure.
flags is reserved for future use.
logicOpEnable controls whether to apply Logical Operations.
logicOp selects which logical operation to apply.
attachmentCount is the number of VkPipelineColorBlendAttachmentState elements in pAttachments. This value must equal the colorAttachmentCount for the subpass in which this pipeline is used.
pAttachments: is a pointer to an array of per target attachment states.
blendConstants is a pointer to an array of four values used as the R, G, B, and A components of the blend constant that are used in blending, depending on the blend factor.

Each element of the pAttachments array is a VkPipelineColorBlendAttachmentState structure specifying per-target blending state for each individual color attachment. If the independent blending feature is not enabled on the device, all VkPipelineColorBlendAttachmentState elements in the pAttachments array must be identical.

Valid Usage

If the independent blending feature is not enabled, all elements of pAttachments must be identical
If the logic operations feature is not enabled, logicOpEnable must be VK_FALSE
If logicOpEnable is VK_TRUE, logicOp must be a valid VkLogicOp value

Valid Usage (Implicit)

sType must be VK_STRUCTURE_TYPE_PIPELINE_COLOR_BLEND_STATE_CREATE_INFO
pNext must be NULL or a pointer to a valid instance of VkPipelineColorBlendAdvancedStateCreateInfoEXT
The sType value of each struct in the pNext chain must be unique
flags must be 0
If attachmentCount is not 0, pAttachments must be a valid pointer to an array of attachmentCount valid VkPipelineColorBlendAttachmentState structures

// Provided by VK_VERSION_1_0
typedef VkFlags VkPipelineColorBlendStateCreateFlags;

VkPipelineColorBlendStateCreateFlags is a bitmask type for setting a mask, but is currently reserved for future use.

The VkPipelineColorBlendAttachmentState structure is defined as:

// Provided by VK_VERSION_1_0
typedef struct VkPipelineColorBlendAttachmentState {
    VkBool32                 blendEnable;
    VkBlendFactor            srcColorBlendFactor;
    VkBlendFactor            dstColorBlendFactor;
    VkBlendOp                colorBlendOp;
    VkBlendFactor            srcAlphaBlendFactor;
    VkBlendFactor            dstAlphaBlendFactor;
    VkBlendOp                alphaBlendOp;
    VkColorComponentFlags    colorWriteMask;
} VkPipelineColorBlendAttachmentState;

blendEnable controls whether blending is enabled for the corresponding color attachment. If blending is not enabled, the source fragment’s color for that attachment is passed through unmodified.
srcColorBlendFactor selects which blend factor is used to determine the source factors (S_r,S_g,S_b).
dstColorBlendFactor selects which blend factor is used to determine the destination factors (D_r,D_g,D_b).
colorBlendOp selects which blend operation is used to calculate the RGB values to write to the color attachment.
srcAlphaBlendFactor selects which blend factor is used to determine the source factor S_a.
dstAlphaBlendFactor selects which blend factor is used to determine the destination factor D_a.
alphaBlendOp selects which blend operation is use to calculate the alpha values to write to the color attachment.
colorWriteMask is a bitmask of VkColorComponentFlagBits specifying which of the R, G, B, and/or A components are enabled for writing, as described for the Color Write Mask.

Valid Usage

If the dual source blending feature is not enabled, srcColorBlendFactor must not be VK_BLEND_FACTOR_SRC1_COLOR, VK_BLEND_FACTOR_ONE_MINUS_SRC1_COLOR, VK_BLEND_FACTOR_SRC1_ALPHA, or VK_BLEND_FACTOR_ONE_MINUS_SRC1_ALPHA
If the dual source blending feature is not enabled, dstColorBlendFactor must not be VK_BLEND_FACTOR_SRC1_COLOR, VK_BLEND_FACTOR_ONE_MINUS_SRC1_COLOR, VK_BLEND_FACTOR_SRC1_ALPHA, or VK_BLEND_FACTOR_ONE_MINUS_SRC1_ALPHA
If the dual source blending feature is not enabled, srcAlphaBlendFactor must not be VK_BLEND_FACTOR_SRC1_COLOR, VK_BLEND_FACTOR_ONE_MINUS_SRC1_COLOR, VK_BLEND_FACTOR_SRC1_ALPHA, or VK_BLEND_FACTOR_ONE_MINUS_SRC1_ALPHA
If the dual source blending feature is not enabled, dstAlphaBlendFactor must not be VK_BLEND_FACTOR_SRC1_COLOR, VK_BLEND_FACTOR_ONE_MINUS_SRC1_COLOR, VK_BLEND_FACTOR_SRC1_ALPHA, or VK_BLEND_FACTOR_ONE_MINUS_SRC1_ALPHA
If either of colorBlendOp or alphaBlendOp is an advanced blend operation, then colorBlendOp must equal alphaBlendOp
If VkPhysicalDeviceBlendOperationAdvancedPropertiesEXT::advancedBlendIndependentBlend is VK_FALSE and colorBlendOp is an advanced blend operation, then colorBlendOp must be the same for all attachments
If VkPhysicalDeviceBlendOperationAdvancedPropertiesEXT::advancedBlendIndependentBlend is VK_FALSE and alphaBlendOp is an advanced blend operation, then alphaBlendOp must be the same for all attachments
If VkPhysicalDeviceBlendOperationAdvancedPropertiesEXT::advancedBlendAllOperations is VK_FALSE, then colorBlendOp must not be VK_BLEND_OP_ZERO_EXT, VK_BLEND_OP_SRC_EXT, VK_BLEND_OP_DST_EXT, VK_BLEND_OP_SRC_OVER_EXT, VK_BLEND_OP_DST_OVER_EXT, VK_BLEND_OP_SRC_IN_EXT, VK_BLEND_OP_DST_IN_EXT, VK_BLEND_OP_SRC_OUT_EXT, VK_BLEND_OP_DST_OUT_EXT, VK_BLEND_OP_SRC_ATOP_EXT, VK_BLEND_OP_DST_ATOP_EXT, VK_BLEND_OP_XOR_EXT, VK_BLEND_OP_INVERT_EXT, VK_BLEND_OP_INVERT_RGB_EXT, VK_BLEND_OP_LINEARDODGE_EXT, VK_BLEND_OP_LINEARBURN_EXT, VK_BLEND_OP_VIVIDLIGHT_EXT, VK_BLEND_OP_LINEARLIGHT_EXT, VK_BLEND_OP_PINLIGHT_EXT, VK_BLEND_OP_HARDMIX_EXT, VK_BLEND_OP_PLUS_EXT, VK_BLEND_OP_PLUS_CLAMPED_EXT, VK_BLEND_OP_PLUS_CLAMPED_ALPHA_EXT, VK_BLEND_OP_PLUS_DARKER_EXT, VK_BLEND_OP_MINUS_EXT, VK_BLEND_OP_MINUS_CLAMPED_EXT, VK_BLEND_OP_CONTRAST_EXT, VK_BLEND_OP_INVERT_OVG_EXT, VK_BLEND_OP_RED_EXT, VK_BLEND_OP_GREEN_EXT, or VK_BLEND_OP_BLUE_EXT
If colorBlendOp or alphaBlendOp is an advanced blend operation, then VkSubpassDescription::colorAttachmentCount of the subpass this pipeline is compiled against must be less than or equal to VkPhysicalDeviceBlendOperationAdvancedPropertiesEXT::advancedBlendMaxColorAttachments

Valid Usage (Implicit)

srcColorBlendFactor must be a valid VkBlendFactor value
dstColorBlendFactor must be a valid VkBlendFactor value
colorBlendOp must be a valid VkBlendOp value
srcAlphaBlendFactor must be a valid VkBlendFactor value
dstAlphaBlendFactor must be a valid VkBlendFactor value
alphaBlendOp must be a valid VkBlendOp value
colorWriteMask must be a valid combination of VkColorComponentFlagBits values

28.1.1. Blend Factors

The source and destination color and alpha blending factors are selected from the enum:

// Provided by VK_VERSION_1_0
typedef enum VkBlendFactor {
    VK_BLEND_FACTOR_ZERO = 0,
    VK_BLEND_FACTOR_ONE = 1,
    VK_BLEND_FACTOR_SRC_COLOR = 2,
    VK_BLEND_FACTOR_ONE_MINUS_SRC_COLOR = 3,
    VK_BLEND_FACTOR_DST_COLOR = 4,
    VK_BLEND_FACTOR_ONE_MINUS_DST_COLOR = 5,
    VK_BLEND_FACTOR_SRC_ALPHA = 6,
    VK_BLEND_FACTOR_ONE_MINUS_SRC_ALPHA = 7,
    VK_BLEND_FACTOR_DST_ALPHA = 8,
    VK_BLEND_FACTOR_ONE_MINUS_DST_ALPHA = 9,
    VK_BLEND_FACTOR_CONSTANT_COLOR = 10,
    VK_BLEND_FACTOR_ONE_MINUS_CONSTANT_COLOR = 11,
    VK_BLEND_FACTOR_CONSTANT_ALPHA = 12,
    VK_BLEND_FACTOR_ONE_MINUS_CONSTANT_ALPHA = 13,
    VK_BLEND_FACTOR_SRC_ALPHA_SATURATE = 14,
    VK_BLEND_FACTOR_SRC1_COLOR = 15,
    VK_BLEND_FACTOR_ONE_MINUS_SRC1_COLOR = 16,
    VK_BLEND_FACTOR_SRC1_ALPHA = 17,
    VK_BLEND_FACTOR_ONE_MINUS_SRC1_ALPHA = 18,
} VkBlendFactor;

The semantics of each enum value is described in the table below:

Table 34. Blend Factors
VkBlendFactor	RGB Blend Factors (S_r,S_g,S_b) or (D_r,D_g,D_b)	Alpha Blend Factor (S_a or D_a)
`VK_BLEND_FACTOR_ZERO`	(0,0,0)	0
`VK_BLEND_FACTOR_ONE`	(1,1,1)	1
`VK_BLEND_FACTOR_SRC_COLOR`	(R_s0,G_s0,B_s0)	A_s0
`VK_BLEND_FACTOR_ONE_MINUS_SRC_COLOR`	(1-R_s0,1-G_s0,1-B_s0)	1-A_s0
`VK_BLEND_FACTOR_DST_COLOR`	(R_d,G_d,B_d)	A_d
`VK_BLEND_FACTOR_ONE_MINUS_DST_COLOR`	(1-R_d,1-G_d,1-B_d)	1-A_d
`VK_BLEND_FACTOR_SRC_ALPHA`	(A_s0,A_s0,A_s0)	A_s0
`VK_BLEND_FACTOR_ONE_MINUS_SRC_ALPHA`	(1-A_s0,1-A_s0,1-A_s0)	1-A_s0
`VK_BLEND_FACTOR_DST_ALPHA`	(A_d,A_d,A_d)	A_d
`VK_BLEND_FACTOR_ONE_MINUS_DST_ALPHA`	(1-A_d,1-A_d,1-A_d)	1-A_d
`VK_BLEND_FACTOR_CONSTANT_COLOR`	(R_c,G_c,B_c)	A_c
`VK_BLEND_FACTOR_ONE_MINUS_CONSTANT_COLOR`	(1-R_c,1-G_c,1-B_c)	1-A_c
`VK_BLEND_FACTOR_CONSTANT_ALPHA`	(A_c,A_c,A_c)	A_c
`VK_BLEND_FACTOR_ONE_MINUS_CONSTANT_ALPHA`	(1-A_c,1-A_c,1-A_c)	1-A_c
`VK_BLEND_FACTOR_SRC_ALPHA_SATURATE`	(f,f,f); f = min(A_s0,1-A_d)	1
`VK_BLEND_FACTOR_SRC1_COLOR`	(R_s1,G_s1,B_s1)	A_s1
`VK_BLEND_FACTOR_ONE_MINUS_SRC1_COLOR`	(1-R_s1,1-G_s1,1-B_s1)	1-A_s1
`VK_BLEND_FACTOR_SRC1_ALPHA`	(A_s1,A_s1,A_s1)	A_s1
`VK_BLEND_FACTOR_ONE_MINUS_SRC1_ALPHA`	(1-A_s1,1-A_s1,1-A_s1)	1-A_s1

In this table, the following conventions are used:

R_s0,G_s0,B_s0 and A_s0 represent the first source color R, G, B, and A components, respectively, for the fragment output location corresponding to the color attachment being blended.
R_s1,G_s1,B_s1 and A_s1 represent the second source color R, G, B, and A components, respectively, used in dual source blending modes, for the fragment output location corresponding to the color attachment being blended.
R_d,G_d,B_d and A_d represent the R, G, B, and A components of the destination color. That is, the color currently in the corresponding color attachment for this fragment/sample.
R_c,G_c,B_c and A_c represent the blend constant R, G, B, and A components, respectively.

If the pipeline state object is created without the VK_DYNAMIC_STATE_BLEND_CONSTANTS dynamic state enabled then the blend constant (R_c,G_c,B_c,A_c) is specified via the blendConstants member of VkPipelineColorBlendStateCreateInfo.

Otherwise, to dynamically set and change the blend constant, call:

// Provided by VK_VERSION_1_0
void vkCmdSetBlendConstants(
    VkCommandBuffer                             commandBuffer,
    const float                                 blendConstants[4]);

commandBuffer is the command buffer into which the command will be recorded.
blendConstants is a pointer to an array of four values specifying the R, G, B, and A components of the blend constant color used in blending, depending on the blend factor.

Valid Usage (Implicit)

commandBuffer must be a valid VkCommandBuffer handle
commandBuffer must be in the recording state
The VkCommandPool that commandBuffer was allocated from must support graphics operations

Host Synchronization

Host access to commandBuffer must be externally synchronized
Host access to the VkCommandPool that commandBuffer was allocated from must be externally synchronized

Command Properties

Command Buffer Levels	Render Pass Scope	Supported Queue Types	Pipeline Type
Primary Secondary	Both	Graphics

Command Buffer Levels

Render Pass Scope

Supported Queue Types

Pipeline Type

Primary
Secondary

Both

Graphics

28.1.2. Dual-Source Blending

Blend factors that use the secondary color input (R_s1,G_s1,B_s1,A_s1) (VK_BLEND_FACTOR_SRC1_COLOR, VK_BLEND_FACTOR_ONE_MINUS_SRC1_COLOR, VK_BLEND_FACTOR_SRC1_ALPHA, and VK_BLEND_FACTOR_ONE_MINUS_SRC1_ALPHA) may consume implementation resources that could otherwise be used for rendering to multiple color attachments. Therefore, the number of color attachments that can be used in a framebuffer may be lower when using dual-source blending.

Dual-source blending is only supported if the dualSrcBlend feature is enabled.

The maximum number of color attachments that can be used in a subpass when using dual-source blending functions is implementation-dependent and is reported as the maxFragmentDualSrcAttachments member of VkPhysicalDeviceLimits.

When using a fragment shader with dual-source blending functions, the color outputs are bound to the first and second inputs of the blender using the Index decoration, as described in Fragment Output Interface. If the second color input to the blender is not written in the shader, or if no output is bound to the second input of a blender, the result of the blending operation is not defined.

28.1.3. Blend Operations

Once the source and destination blend factors have been selected, they along with the source and destination components are passed to the blending operations. RGB and alpha components can use different operations. Possible values of VkBlendOp, specifying the operations, are:

// Provided by VK_VERSION_1_0
typedef enum VkBlendOp {
    VK_BLEND_OP_ADD = 0,
    VK_BLEND_OP_SUBTRACT = 1,
    VK_BLEND_OP_REVERSE_SUBTRACT = 2,
    VK_BLEND_OP_MIN = 3,
    VK_BLEND_OP_MAX = 4,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_ZERO_EXT = 1000148000,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_SRC_EXT = 1000148001,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_DST_EXT = 1000148002,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_SRC_OVER_EXT = 1000148003,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_DST_OVER_EXT = 1000148004,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_SRC_IN_EXT = 1000148005,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_DST_IN_EXT = 1000148006,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_SRC_OUT_EXT = 1000148007,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_DST_OUT_EXT = 1000148008,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_SRC_ATOP_EXT = 1000148009,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_DST_ATOP_EXT = 1000148010,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_XOR_EXT = 1000148011,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_MULTIPLY_EXT = 1000148012,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_SCREEN_EXT = 1000148013,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_OVERLAY_EXT = 1000148014,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_DARKEN_EXT = 1000148015,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_LIGHTEN_EXT = 1000148016,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_COLORDODGE_EXT = 1000148017,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_COLORBURN_EXT = 1000148018,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_HARDLIGHT_EXT = 1000148019,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_SOFTLIGHT_EXT = 1000148020,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_DIFFERENCE_EXT = 1000148021,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_EXCLUSION_EXT = 1000148022,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_INVERT_EXT = 1000148023,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_INVERT_RGB_EXT = 1000148024,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_LINEARDODGE_EXT = 1000148025,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_LINEARBURN_EXT = 1000148026,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_VIVIDLIGHT_EXT = 1000148027,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_LINEARLIGHT_EXT = 1000148028,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_PINLIGHT_EXT = 1000148029,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_HARDMIX_EXT = 1000148030,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_HSL_HUE_EXT = 1000148031,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_HSL_SATURATION_EXT = 1000148032,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_HSL_COLOR_EXT = 1000148033,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_HSL_LUMINOSITY_EXT = 1000148034,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_PLUS_EXT = 1000148035,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_PLUS_CLAMPED_EXT = 1000148036,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_PLUS_CLAMPED_ALPHA_EXT = 1000148037,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_PLUS_DARKER_EXT = 1000148038,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_MINUS_EXT = 1000148039,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_MINUS_CLAMPED_EXT = 1000148040,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_CONTRAST_EXT = 1000148041,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_INVERT_OVG_EXT = 1000148042,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_RED_EXT = 1000148043,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_GREEN_EXT = 1000148044,
  // Provided by VK_EXT_blend_operation_advanced
    VK_BLEND_OP_BLUE_EXT = 1000148045,
} VkBlendOp;

The semantics of each basic blend operations is described in the table below:

Table 35. Basic Blend Operations
VkBlendOp	RGB Components	Alpha Component
`VK_BLEND_OP_ADD`	R = R_s0 × S_r + R_d × D_r G = G_s0 × S_g + G_d × D_g B = B_s0 × S_b + B_d × D_b	A = A_s0 × S_a + A_d × D_a
`VK_BLEND_OP_SUBTRACT`	R = R_s0 × S_r - R_d × D_r G = G_s0 × S_g - G_d × D_g B = B_s0 × S_b - B_d × D_b	A = A_s0 × S_a - A_d × D_a
`VK_BLEND_OP_REVERSE_SUBTRACT`	R = R_d × D_r - R_s0 × S_r G = G_d × D_g - G_s0 × S_g B = B_d × D_b - B_s0 × S_b	A = A_d × D_a - A_s0 × S_a
`VK_BLEND_OP_MIN`	R = min(R_s0,R_d) G = min(G_s0,G_d) B = min(B_s0,B_d)	A = min(A_s0,A_d)
`VK_BLEND_OP_MAX`	R = max(R_s0,R_d) G = max(G_s0,G_d) B = max(B_s0,B_d)	A = max(A_s0,A_d)

In this table, the following conventions are used:

R_s0, G_s0, B_s0 and A_s0 represent the first source color R, G, B, and A components, respectively.
R_d, G_d, B_d and A_d represent the R, G, B, and A components of the destination color. That is, the color currently in the corresponding color attachment for this fragment/sample.
S_r, S_g, S_b and S_a represent the source blend factor R, G, B, and A components, respectively.
D_r, D_g, D_b and D_a represent the destination blend factor R, G, B, and A components, respectively.

The blending operation produces a new set of values R, G, B and A, which are written to the framebuffer attachment. If blending is not enabled for this attachment, then R, G, B and A are assigned R_s0, G_s0, B_s0 and A_s0, respectively.

If the color attachment is fixed-point, the components of the source and destination values and blend factors are each clamped to [0,1] or [-1,1] respectively for an unsigned normalized or signed normalized color attachment prior to evaluating the blend operations. If the color attachment is floating-point, no clamping occurs.

If the numeric format of a framebuffer attachment uses sRGB encoding, the R, G, and B destination color values (after conversion from fixed-point to floating-point) are considered to be encoded for the sRGB color space and hence are linearized prior to their use in blending. Each R, G, and B component is converted from nonlinear to linear as described in the “sRGB EOTF” section of the Khronos Data Format Specification. If the format is not sRGB, no linearization is performed.

If the numeric format of a framebuffer attachment uses sRGB encoding, then the final R, G and B values are converted into the nonlinear sRGB representation before being written to the framebuffer attachment as described in the “sRGB EOTF^-1” section of the Khronos Data Format Specification.

If the framebuffer color attachment numeric format is not sRGB encoded then the resulting c_s values for R, G and B are unmodified. The value of A is never sRGB encoded. That is, the alpha component is always stored in memory as linear.

If the framebuffer color attachment is VK_ATTACHMENT_UNUSED, no writes are performed through that attachment. Framebuffer color attachments greater than or equal to VkSubpassDescription::colorAttachmentCount perform no writes.

28.1.4. Advanced Blend Operations

The advanced blend operations are those listed in tables f/X/Y/Z Advanced Blend Operations, Hue-Saturation-Luminosity Advanced Blend Operations, and Additional RGB Blend Operations.

If the pNext chain of VkPipelineColorBlendStateCreateInfo includes a VkPipelineColorBlendAdvancedStateCreateInfoEXT structure, then that structure includes parameters that affect advanced blend operations.

The VkPipelineColorBlendAdvancedStateCreateInfoEXT structure is defined as:

// Provided by VK_EXT_blend_operation_advanced
typedef struct VkPipelineColorBlendAdvancedStateCreateInfoEXT {
    VkStructureType      sType;
    const void*          pNext;
    VkBool32             srcPremultiplied;
    VkBool32             dstPremultiplied;
    VkBlendOverlapEXT    blendOverlap;
} VkPipelineColorBlendAdvancedStateCreateInfoEXT;

sType is the type of this structure.
pNext is NULL or a pointer to a structure extending this structure.
srcPremultiplied specifies whether the source color of the blend operation is treated as premultiplied.
dstPremultiplied specifies whether the destination color of the blend operation is treated as premultiplied.
blendOverlap is a VkBlendOverlapEXT value specifying how the source and destination sample’s coverage is correlated.

If this structure is not present, srcPremultiplied and dstPremultiplied are both considered to be VK_TRUE, and blendOverlap is considered to be VK_BLEND_OVERLAP_UNCORRELATED_EXT.

Valid Usage

If the non-premultiplied source color property is not supported, srcPremultiplied must be VK_TRUE
If the non-premultiplied destination color property is not supported, dstPremultiplied must be VK_TRUE
If the correlated overlap property is not supported, blendOverlap must be VK_BLEND_OVERLAP_UNCORRELATED_EXT

Valid Usage (Implicit)

sType must be VK_STRUCTURE_TYPE_PIPELINE_COLOR_BLEND_ADVANCED_STATE_CREATE_INFO_EXT
blendOverlap must be a valid VkBlendOverlapEXT value

When using one of the operations in table f/X/Y/Z Advanced Blend Operations or Hue-Saturation-Luminosity Advanced Blend Operations, blending is performed according to the following equations:

R G B A = = = = f (R_{s}^{'}, R_{d}^{'}) * p_{0} (A_{s}, A_{d}) f (G_{s}^{'}, G_{d}^{'}) * p_{0} (A_{s}, A_{d}) f (B_{s}^{'}, B_{d}^{'}) * p_{0} (A_{s}, A_{d}) X * p_{0} (A_{s}, A_{d}) + + + + Y * R_{s}^{'} * p_{1} (A_{s}, A_{d}) Y * G_{s}^{'} * p_{1} (A_{s}, A_{d}) Y * B_{s}^{'} * p_{1} (A_{s}, A_{d}) Y * p_{1} (A_{s}, A_{d}) + + + + Z * R_{d}^{'} * p_{2} (A_{s}, A_{d}) Z * G_{d}^{'} * p_{2} (A_{s}, A_{d}) Z * B_{d}^{'} * p_{2} (A_{s}, A_{d}) Z * p_{2} (A_{s}, A_{d})

where the function f and terms X, Y, and Z are specified in the table. The R, G, and B components of the source color used for blending are derived according to srcPremultiplied. If srcPremultiplied is set to VK_TRUE, the fragment color components are considered to have been premultiplied by the A component prior to blending. The base source color (R_s',G_s',B_s') is obtained by dividing through by the A component:

(R_{s}^{'}, G_{s}^{'}, B_{s}^{'}) = {(0, 0, 0) (\frac{R _{s}}{A _{s}}, \frac{G _{s}}{A _{s}}, \frac{B _{s}}{A _{s}}) A_{s} = 0 otherwise

If srcPremultiplied is VK_FALSE, the fragment color components are used as the base color:

(R_{s}^{'}, G_{s}^{'}, B_{s}^{'}) = (R_{s}, G_{s}, B_{s})

The R, G, and B components of the destination color used for blending are derived according to dstPremultiplied. If dstPremultiplied is set to VK_TRUE, the destination components are considered to have been premultiplied by the A component prior to blending. The base destination color (R_d',G_d',B_d') is obtained by dividing through by the A component:

(R_{d}^{'}, G_{d}^{'}, B_{d}^{'}) = {(0, 0, 0) (\frac{R _{d}}{A _{d}}, \frac{G _{d}}{A _{d}}, \frac{B _{d}}{A _{d}}) A_{d} = 0 otherwise

If dstPremultiplied is VK_FALSE, the destination color components are used as the base color:

(R_{d}^{'}, G_{d}^{'}, B_{d}^{'}) = (R_{d}, G_{d}, B_{d})

When blending using advanced blend operations, we expect that the R, G, and B components of premultiplied source and destination color inputs be stored as the product of non-premultiplied R, G, and B component values and the A component of the color. If any R, G, or B component of a premultiplied input color is non-zero and the A component is zero, the color is considered ill-formed, and the corresponding component of the blend result is undefined.

All of the advanced blend operation formulas in this chapter compute the result as a premultiplied color. If dstPremultiplied is VK_FALSE, that result color’s R, G, and B components are divided by the A component before being written to the framebuffer. If any R, G, or B component of the color is non-zero and the A component is zero, the result is considered ill-formed, and the corresponding component of the blend result is undefined. If all components are zero, that value is unchanged.

If the A component of any input or result color is less than zero, the color is considered ill-formed, and all components of the blend result are undefined.

The weighting functions p₀, p₁, and p₂ are defined in table Advanced Blend Overlap Modes. In these functions, the A components of the source and destination colors are taken to indicate the portion of the pixel covered by the fragment (source) and the fragments previously accumulated in the pixel (destination). The functions p₀, p₁, and p₂ approximate the relative portion of the pixel covered by the intersection of the source and destination, covered only by the source, and covered only by the destination, respectively.

Possible values of VkPipelineColorBlendAdvancedStateCreateInfoEXT::blendOverlap, specifying the blend overlap functions, are:

// Provided by VK_EXT_blend_operation_advanced
typedef enum VkBlendOverlapEXT {
    VK_BLEND_OVERLAP_UNCORRELATED_EXT = 0,
    VK_BLEND_OVERLAP_DISJOINT_EXT = 1,
    VK_BLEND_OVERLAP_CONJOINT_EXT = 2,
} VkBlendOverlapEXT;

VK_BLEND_OVERLAP_UNCORRELATED_EXT specifies that there is no correlation between the source and destination coverage.
VK_BLEND_OVERLAP_CONJOINT_EXT specifies that the source and destination coverage are considered to have maximal overlap.
VK_BLEND_OVERLAP_DISJOINT_EXT specifies that the source and destination coverage are considered to have minimal overlap.

Table 36. Advanced Blend Overlap Modes
Overlap Mode	Weighting Equations
`VK_BLEND_OVERLAP_UNCORRELATED_EXT`	$p_{0} (A_{s}, A_{d}) p_{1} (A_{s}, A_{d}) p_{2} (A_{s}, A_{d}) = A_{s} A_{d} = A_{s} (1 - A_{d}) = A_{d} (1 - A_{s})$
`VK_BLEND_OVERLAP_CONJOINT_EXT`	$p_{0} (A_{s}, A_{d}) p_{1} (A_{s}, A_{d}) p_{2} (A_{s}, A_{d}) = m i n (A_{s}, A_{d}) = m a x (A_{s} - A_{d}, 0) = m a x (A_{d} - A_{s}, 0)$
`VK_BLEND_OVERLAP_DISJOINT_EXT`	$p_{0} (A_{s}, A_{d}) p_{1} (A_{s}, A_{d}) p_{2} (A_{s}, A_{d}) = m a x (A_{s} + A_{d} - 1, 0) = m i n (A_{s}, 1 - A_{d}) = m i n (A_{d}, 1 - A_{s})$

Table 37. f/X/Y/Z Advanced Blend Operations
Mode	Blend Coefficients
`VK_BLEND_OP_ZERO_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (0, 0, 0) = 0$
`VK_BLEND_OP_SRC_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 0) = C_{s}$
`VK_BLEND_OP_DST_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 0, 1) = C_{d}$
`VK_BLEND_OP_SRC_OVER_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = C_{s}$
`VK_BLEND_OP_DST_OVER_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = C_{d}$
`VK_BLEND_OP_SRC_IN_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 0, 0) = C_{s}$
`VK_BLEND_OP_DST_IN_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 0, 0) = C_{d}$
`VK_BLEND_OP_SRC_OUT_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (0, 1, 0) = 0$
`VK_BLEND_OP_DST_OUT_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (0, 0, 1) = 0$
`VK_BLEND_OP_SRC_ATOP_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 0, 1) = C_{s}$
`VK_BLEND_OP_DST_ATOP_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 0) = C_{d}$
`VK_BLEND_OP_XOR_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (0, 1, 1) = 0$
`VK_BLEND_OP_MULTIPLY_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = C_{s} C_{d}$
`VK_BLEND_OP_SCREEN_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = C_{s} + C_{d} - C_{s} C_{d}$
`VK_BLEND_OP_OVERLAY_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = {2 C_{s} C_{d} 1 - 2 (1 - C_{s}) (1 - C_{d}) C_{d} \leq 0.5 otherwise$
`VK_BLEND_OP_DARKEN_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = m i n (C_{s}, C_{d})$
`VK_BLEND_OP_LIGHTEN_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = m a x (C_{s}, C_{d})$
`VK_BLEND_OP_COLORDODGE_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = ⎩ ⎪ ⎪ ⎨ ⎪ ⎪ ⎧ 0 m i n (1, \frac{C _{d}}{1 - C _{s}}) 1 C_{d} \leq 0 C_{d} > 0 and C_{s} < 1 C_{d} > 0 and C_{s} \geq 1$
`VK_BLEND_OP_COLORBURN_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = ⎩ ⎪ ⎪ ⎨ ⎪ ⎪ ⎧ 1 1 - m i n (1, \frac{1 - C _{d}}{C _{s}}) 0 C_{d} \geq 1 C_{d} < 1 and C_{s} > 0 C_{d} < 1 and C_{s} \leq 0$
`VK_BLEND_OP_HARDLIGHT_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = {2 C_{s} C_{d} 1 - 2 (1 - C_{s}) (1 - C_{d}) C_{s} \leq 0.5 otherwise$
`VK_BLEND_OP_SOFTLIGHT_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = ⎩ ⎪ ⎪ ⎨ ⎪ ⎪ ⎧ C_{d} - (1 - 2 C_{s}) C_{d} (1 - C_{d}) C_{d} + (2 C_{s} - 1) C_{d} ((16 C_{d} - 12) C_{d} + 3) C_{d} + (2 C_{s} - 1) (C_{d} - C_{d}) C_{s} \leq 0.5 C_{s} > 0.5 and C_{d} \leq 0.25 C_{s} > 0.5 and C_{d} > 0.25$
`VK_BLEND_OP_DIFFERENCE_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = ∣ C_{d} - C_{s} ∣$
`VK_BLEND_OP_EXCLUSION_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = C_{s} + C_{d} - 2 C_{s} C_{d}$
`VK_BLEND_OP_INVERT_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 0, 1) = 1 - C_{d}$
`VK_BLEND_OP_INVERT_RGB_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 0, 1) = C_{s} (1 - C_{d})$
`VK_BLEND_OP_LINEARDODGE_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = {C_{s} + C_{d} 1 C_{s} + C_{d} \leq 1 otherwise$
`VK_BLEND_OP_LINEARBURN_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = {C_{s} + C_{d} - 1 0 C_{s} + C_{d} > 1 otherwise$
`VK_BLEND_OP_VIVIDLIGHT_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = ⎩ ⎪ ⎪ ⎪ ⎪ ⎨ ⎪ ⎪ ⎪ ⎪ ⎧ 1 - m i n (1, \frac{1 - C _{d}}{2 C _{s}}) 0 m i n (1, \frac{C _{d}}{2 ( 1 - C _{s} )}) 1 0 < C_{s} < 0.5 C_{s} \leq 0 0.5 \leq C_{s} < 1 C_{s} \geq 1$
`VK_BLEND_OP_LINEARLIGHT_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = ⎩ ⎪ ⎪ ⎨ ⎪ ⎪ ⎧ 1 2 C_{s} + C_{d} - 1 0 2 C_{s} + C_{d} > 2 1 < 2 C_{s} + C_{d} \leq 2 2 C_{s} + C_{d} \leq 1$
`VK_BLEND_OP_PINLIGHT_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = ⎩ ⎪ ⎪ ⎪ ⎪ ⎨ ⎪ ⎪ ⎪ ⎪ ⎧ 0 2 C_{s} - 1 2 C_{s} C_{d} 2 C_{s} - 1 > C_{d} and C_{s} < 0.5 2 C_{s} - 1 > C_{d} and C_{s} \geq 0.5 2 C_{s} - 1 \leq C_{d} and C_{s} < 0.5 C_{d} 2 C_{s} - 1 \leq C_{d} and C_{s} \geq 0.5 C_{d}$
`VK_BLEND_OP_HARDMIX_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = {01 C_{s} + C_{d} < 1 otherwise$

When using one of the HSL blend operations in table Hue-Saturation-Luminosity Advanced Blend Operations as the blend operation, the RGB color components produced by the function f are effectively obtained by converting both the non-premultiplied source and destination colors to the HSL (hue, saturation, luminosity) color space, generating a new HSL color by selecting H, S, and L components from the source or destination according to the blend operation, and then converting the result back to RGB. In the equations below, a blended RGB color is produced according to the following pseudocode:

  float minv3(vec3 c) {
    return min(min(c.r, c.g), c.b);
  }
  float maxv3(vec3 c) {
    return max(max(c.r, c.g), c.b);
  }
  float lumv3(vec3 c) {
    return dot(c, vec3(0.30, 0.59, 0.11));
  }
  float satv3(vec3 c) {
    return maxv3(c) - minv3(c);
  }

  // If any color components are outside [0,1], adjust the color to
  // get the components in range.
  vec3 ClipColor(vec3 color) {
    float lum = lumv3(color);
    float mincol = minv3(color);
    float maxcol = maxv3(color);
    if (mincol < 0.0) {
      color = lum + ((color-lum)*lum) / (lum-mincol);
    }
    if (maxcol > 1.0) {
      color = lum + ((color-lum)*(1-lum)) / (maxcol-lum);
    }
    return color;
  }

  // Take the base RGB color <cbase> and override its luminosity
  // with that of the RGB color <clum>.
  vec3 SetLum(vec3 cbase, vec3 clum) {
    float lbase = lumv3(cbase);
    float llum = lumv3(clum);
    float ldiff = llum - lbase;
    vec3 color = cbase + vec3(ldiff);
    return ClipColor(color);
  }

  // Take the base RGB color <cbase> and override its saturation with
  // that of the RGB color <csat>.  The override the luminosity of the
  // result with that of the RGB color <clum>.
  vec3 SetLumSat(vec3 cbase, vec3 csat, vec3 clum)
  {
    float minbase = minv3(cbase);
    float sbase = satv3(cbase);
    float ssat = satv3(csat);
    vec3 color;
    if (sbase > 0) {
      // Equivalent (modulo rounding errors) to setting the
      // smallest (R,G,B) component to 0, the largest to <ssat>,
      // and interpolating the "middle" component based on its
      // original value relative to the smallest/largest.
      color = (cbase - minbase) * ssat / sbase;
    } else {
      color = vec3(0.0);
    }
    return SetLum(color, clum);
  }

Table 38. Hue-Saturation-Luminosity Advanced Blend Operations
Mode	Result
`VK_BLEND_OP_HSL_HUE_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = S e t L u m S a t (C_{s}, C_{d}, C_{d})$
`VK_BLEND_OP_HSL_SATURATION_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = S e t L u m S a t (C_{d}, C_{s}, C_{d})$
`VK_BLEND_OP_HSL_COLOR_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = S e t L u m (C_{s}, C_{d})$
`VK_BLEND_OP_HSL_LUMINOSITY_EXT`	$(X, Y, Z) f (C_{s}, C_{d}) = (1, 1, 1) = S e t L u m (C_{d}, C_{s})$

When using one of the operations in table Additional RGB Blend Operations as the blend operation, the source and destination colors used by these blending operations are interpreted according to srcPremultiplied and dstPremultiplied. The blending operations below are evaluated where the RGB source and destination color components are both considered to have been premultiplied by the corresponding A component.

(R_{s}^{'}, G_{s}^{'}, B_{s}^{'}) (R_{d}^{'}, G_{d}^{'}, B_{d}^{'}) = {(R_{s}, G_{s}, B_{s}) (R_{s} A_{s}, G_{s} A_{s}, B_{s} A_{s}) if srcPremultiplied is VK_TRUE if srcPremultiplied is VK_FALSE = {(R_{d}, G_{d}, B_{d}) (R_{d} A_{d}, G_{d} A_{d}, B_{d} A_{d}) if dstPremultiplied is VK_TRUE if dstPremultiplied is VK_FALSE

Table 39. Additional RGB Blend Operations
Mode	Result
`VK_BLEND_OP_PLUS_EXT`	$(R, G, B, A) = (R_{s}^{'} + R_{d}^{'}, G_{s}^{'} + G_{d}^{'}, B_{s}^{'} + B_{d}^{'}, A_{s} + A_{d})$
`VK_BLEND_OP_PLUS_CLAMPED_EXT`	$(R, G, B, A) = (m i n (1, R_{s}^{'} + R_{d}^{'}), m i n (1, G_{s}^{'} + G_{d}^{'}), m i n (1, B_{s}^{'} + B_{d}^{'}), m i n (1, A_{s} + A_{d}))$
`VK_BLEND_OP_PLUS_CLAMPED_ALPHA_EXT`	$(R, G, B, A) = (m i n (m i n (1, A_{s} + A_{d}), R_{s}^{'} + R_{d}^{'}), m i n (m i n (1, A_{s} + A_{d}), G_{s}^{'} + G_{d}^{'}), m i n (m i n (1, A_{s} + A_{d}), B_{s}^{'} + B_{d}^{'}), m i n (1, A_{s} + A_{d}))$
`VK_BLEND_OP_PLUS_DARKER_EXT`	$(R, G, B, A) = (m a x (0, m i n (1, A_{s} + A_{d}) - ((A_{s} - R_{s}^{'}) + (A_{d} - R_{d}^{'}))), m a x (0, m i n (1, A_{s} + A_{d}) - ((A_{s} - G_{s}^{'}) + (A_{d} - G_{d}^{'}))), m a x (0, m i n (1, A_{s} + A_{d}) - ((A_{s} - B_{s}^{'}) + (A_{d} - B_{d}^{'}))), m i n (1, A_{s} + A_{d}))$
`VK_BLEND_OP_MINUS_EXT`	$(R, G, B, A) = (R_{d}^{'} - R_{s}^{'}, G_{d}^{'} - G_{s}^{'}, B_{d}^{'} - B_{s}^{'}, A_{d} - A_{s})$
`VK_BLEND_OP_MINUS_CLAMPED_EXT`	$(R, G, B, A) = (m a x (0, R_{d}^{'} - R_{s}^{'}), m a x (0, G_{d}^{'} - G_{s}^{'}), m a x (0, B_{d}^{'} - B_{s}^{'}), m a x (0, A_{d} - A_{s}))$
`VK_BLEND_OP_CONTRAST_EXT`	$(R, G, B, A) = (\frac{A _{d}}{2} + 2 (R_{d}^{'} - \frac{A _{d}}{2}) (R_{s}^{'} - \frac{A _{s}}{2}), \frac{A _{d}}{2} + 2 (G_{d}^{'} - \frac{A _{d}}{2}) (G_{s}^{'} - \frac{A _{s}}{2}), \frac{A _{d}}{2} + 2 (B_{d}^{'} - \frac{A _{d}}{2}) (B_{s}^{'} - \frac{A _{s}}{2}), A_{d})$
`VK_BLEND_OP_INVERT_OVG_EXT`	$(R, G, B, A) = (A_{s} (1 - R_{d}^{'}) + (1 - A_{s}) R_{d}^{'}, A_{s} (1 - G_{d}^{'}) + (1 - A_{s}) G_{d}^{'}, A_{s} (1 - B_{d}^{'}) + (1 - A_{s}) B_{d}^{'}, A_{s} + A_{d} - A_{s} A_{d})$
`VK_BLEND_OP_RED_EXT`	$(R, G, B, A) = (R_{s}^{'}, G_{d}^{'}, B_{d}^{'}, A_{d})$
`VK_BLEND_OP_GREEN_EXT`	$(R, G, B, A) = (R_{d}^{'}, G_{s}^{'}, B_{d}^{'}, A_{d})$
`VK_BLEND_OP_BLUE_EXT`	$(R, G, B, A) = (R_{d}^{'}, G_{d}^{'}, B_{s}^{'}, A_{d})$

28.2. Logical Operations

The application can enable a logical operation between the fragment’s color values and the existing value in the framebuffer attachment. This logical operation is applied prior to updating the framebuffer attachment. Logical operations are applied only for signed and unsigned integer and normalized integer framebuffers. Logical operations are not applied to floating-point or sRGB format color attachments.

Logical operations are controlled by the logicOpEnable and logicOp members of VkPipelineColorBlendStateCreateInfo. If logicOpEnable is VK_TRUE, then a logical operation selected by logicOp is applied between each color attachment and the fragment’s corresponding output value, and blending of all attachments is treated as if it were disabled. Any attachments using color formats for which logical operations are not supported simply pass through the color values unmodified. The logical operation is applied independently for each of the red, green, blue, and alpha components. The logicOp is selected from the following operations:

// Provided by VK_VERSION_1_0
typedef enum VkLogicOp {
    VK_LOGIC_OP_CLEAR = 0,
    VK_LOGIC_OP_AND = 1,
    VK_LOGIC_OP_AND_REVERSE = 2,
    VK_LOGIC_OP_COPY = 3,
    VK_LOGIC_OP_AND_INVERTED = 4,
    VK_LOGIC_OP_NO_OP = 5,
    VK_LOGIC_OP_XOR = 6,
    VK_LOGIC_OP_OR = 7,
    VK_LOGIC_OP_NOR = 8,
    VK_LOGIC_OP_EQUIVALENT = 9,
    VK_LOGIC_OP_INVERT = 10,
    VK_LOGIC_OP_OR_REVERSE = 11,
    VK_LOGIC_OP_COPY_INVERTED = 12,
    VK_LOGIC_OP_OR_INVERTED = 13,
    VK_LOGIC_OP_NAND = 14,
    VK_LOGIC_OP_SET = 15,
} VkLogicOp;

The logical operations supported by Vulkan are summarized in the following table in which

¬ is bitwise invert,
∧ is bitwise and,
∨ is bitwise or,
⊕ is bitwise exclusive or,
s is the fragment’s R_s0, G_s0, B_s0 or A_s0 component value for the fragment output corresponding to the color attachment being updated, and
d is the color attachment’s R, G, B or A component value:

Table 40. Logical Operations
Mode	Operation
`VK_LOGIC_OP_CLEAR`	0
`VK_LOGIC_OP_AND`	s ∧ d
`VK_LOGIC_OP_AND_REVERSE`	s ∧ ¬ d
`VK_LOGIC_OP_COPY`	s
`VK_LOGIC_OP_AND_INVERTED`	¬ s ∧ d
`VK_LOGIC_OP_NO_OP`	d
`VK_LOGIC_OP_XOR`	s ⊕ d
`VK_LOGIC_OP_OR`	s ∨ d
`VK_LOGIC_OP_NOR`	¬ (s ∨ d)
`VK_LOGIC_OP_EQUIVALENT`	¬ (s ⊕ d)
`VK_LOGIC_OP_INVERT`	¬ d
`VK_LOGIC_OP_OR_REVERSE`	s ∨ ¬ d
`VK_LOGIC_OP_COPY_INVERTED`	¬ s
`VK_LOGIC_OP_OR_INVERTED`	¬ s ∨ d
`VK_LOGIC_OP_NAND`	¬ (s ∧ d)
`VK_LOGIC_OP_SET`	all 1s

The result of the logical operation is then written to the color attachment as controlled by the component write mask, described in Blend Operations.

28.3. Color Write Mask

Bits which can be set in VkPipelineColorBlendAttachmentState::colorWriteMask to determine whether the final color values R, G, B and A are written to the framebuffer attachment are:

// Provided by VK_VERSION_1_0
typedef enum VkColorComponentFlagBits {
    VK_COLOR_COMPONENT_R_BIT = 0x00000001,
    VK_COLOR_COMPONENT_G_BIT = 0x00000002,
    VK_COLOR_COMPONENT_B_BIT = 0x00000004,
    VK_COLOR_COMPONENT_A_BIT = 0x00000008,
} VkColorComponentFlagBits;

VK_COLOR_COMPONENT_R_BIT specifies that the R value is written to the color attachment for the appropriate sample. Otherwise, the value in memory is unmodified.
VK_COLOR_COMPONENT_G_BIT specifies that the G value is written to the color attachment for the appropriate sample. Otherwise, the value in memory is unmodified.
VK_COLOR_COMPONENT_B_BIT specifies that the B value is written to the color attachment for the appropriate sample. Otherwise, the value in memory is unmodified.
VK_COLOR_COMPONENT_A_BIT specifies that the A value is written to the color attachment for the appropriate sample. Otherwise, the value in memory is unmodified.

The color write mask operation is applied regardless of whether blending is enabled.

// Provided by VK_VERSION_1_0
typedef VkFlags VkColorComponentFlags;

VkColorComponentFlags is a bitmask type for setting a mask of zero or more VkColorComponentFlagBits.