Vulkan® 1.3.271 - A Specification (with KHR extensions)

27. The Framebuffer

27.1. 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.

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 a VkStructureType value identifying 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.
pAttachments is a pointer to an array of VkPipelineColorBlendAttachmentState structures defining blend state for each color attachment.
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.

Valid Usage

VUID-VkPipelineColorBlendStateCreateInfo-pAttachments-00605
If the independentBlend feature is not enabled, all elements of pAttachments must be identical
VUID-VkPipelineColorBlendStateCreateInfo-logicOpEnable-00606
If the logicOp feature is not enabled, logicOpEnable must be VK_FALSE
VUID-VkPipelineColorBlendStateCreateInfo-logicOpEnable-00607
If logicOpEnable is VK_TRUE, logicOp must be a valid VkLogicOp value
VUID-VkPipelineColorBlendStateCreateInfo-pAttachments-07353
If attachmentCount is not 0 pAttachments must be a valid pointer to an array of attachmentCount valid VkPipelineColorBlendAttachmentState structures

Valid Usage (Implicit)

VUID-VkPipelineColorBlendStateCreateInfo-sType-sType
sType must be VK_STRUCTURE_TYPE_PIPELINE_COLOR_BLEND_STATE_CREATE_INFO
VUID-VkPipelineColorBlendStateCreateInfo-pNext-pNext
pNext must be NULL
VUID-VkPipelineColorBlendStateCreateInfo-flags-zerobitmask
flags must be 0
VUID-VkPipelineColorBlendStateCreateInfo-pAttachments-parameter
If attachmentCount is not 0, and pAttachments is not NULL, 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 used 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

VUID-VkPipelineColorBlendAttachmentState-srcColorBlendFactor-00608
If the dualSrcBlend 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
VUID-VkPipelineColorBlendAttachmentState-dstColorBlendFactor-00609
If the dualSrcBlend 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
VUID-VkPipelineColorBlendAttachmentState-srcAlphaBlendFactor-00610
If the dualSrcBlend 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
VUID-VkPipelineColorBlendAttachmentState-dstAlphaBlendFactor-00611
If the dualSrcBlend 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
VUID-VkPipelineColorBlendAttachmentState-constantAlphaColorBlendFactors-04454
If the VK_KHR_portability_subset extension is enabled, and VkPhysicalDevicePortabilitySubsetFeaturesKHR::constantAlphaColorBlendFactors is VK_FALSE, srcColorBlendFactor must not be VK_BLEND_FACTOR_CONSTANT_ALPHA or VK_BLEND_FACTOR_ONE_MINUS_CONSTANT_ALPHA
VUID-VkPipelineColorBlendAttachmentState-constantAlphaColorBlendFactors-04455
If the VK_KHR_portability_subset extension is enabled, and VkPhysicalDevicePortabilitySubsetFeaturesKHR::constantAlphaColorBlendFactors is VK_FALSE, dstColorBlendFactor must not be VK_BLEND_FACTOR_CONSTANT_ALPHA or VK_BLEND_FACTOR_ONE_MINUS_CONSTANT_ALPHA

Valid Usage (Implicit)

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

27.1.1. 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 the enum values are described in the table below:

Table 33. 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.

To dynamically set and change the blend constants, 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_c, G_c, B_c, and A_c components of the blend constant color used in blending, depending on the blend factor.

This command sets blend constants for subsequent drawing commands when the graphics pipeline is created with VK_DYNAMIC_STATE_BLEND_CONSTANTS set in VkPipelineDynamicStateCreateInfo::pDynamicStates. Otherwise, this state is specified by the VkPipelineColorBlendStateCreateInfo::blendConstants values used to create the currently active pipeline.

Valid Usage (Implicit)

VUID-vkCmdSetBlendConstants-commandBuffer-parameter
commandBuffer must be a valid VkCommandBuffer handle
VUID-vkCmdSetBlendConstants-commandBuffer-recording
commandBuffer must be in the recording state
VUID-vkCmdSetBlendConstants-commandBuffer-cmdpool
The VkCommandPool that commandBuffer was allocated from must support graphics operations
VUID-vkCmdSetBlendConstants-videocoding
This command must only be called outside of a video coding scope

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	Video Coding Scope	Supported Queue Types	Command Type
Primary Secondary	Both	Outside	Graphics	State

Command Buffer Levels

Render Pass Scope

Video Coding Scope

Supported Queue Types

Command Type

Primary
Secondary

Both

Outside

Graphics

State

27.1.2. 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.

Color outputs can be 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 value of the second input is undefined.

27.1.3. 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,
} VkBlendOp;

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

Table 34. 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 numeric format of a framebuffer color attachment 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. Writes are not performed to framebuffer color attachments greater than or equal to the VkSubpassDescription::colorAttachmentCount or VkSubpassDescription2::colorAttachmentCount value.

27.2. 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 35. 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.

27.3. Color Write Mask

Bits which can be set in VkPipelineColorBlendAttachmentState::colorWriteMask, determining 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.