VkAccessFlagBits(3)

# VkAccessFlagBits(3) Manual Page

## Name

VkAccessFlagBits - Bitmask specifying memory access types that will participate in a memory dependency

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## C Specification

The `VkAccessFlagBits` enums is defined as:

    // Provided by VK_VERSION_1_0
    typedef enum VkAccessFlagBits {
        VK_ACCESS_INDIRECT_COMMAND_READ_BIT = 0x00000001,
        VK_ACCESS_INDEX_READ_BIT = 0x00000002,
        VK_ACCESS_VERTEX_ATTRIBUTE_READ_BIT = 0x00000004,
        VK_ACCESS_UNIFORM_READ_BIT = 0x00000008,
        VK_ACCESS_INPUT_ATTACHMENT_READ_BIT = 0x00000010,
        VK_ACCESS_SHADER_READ_BIT = 0x00000020,
        VK_ACCESS_SHADER_WRITE_BIT = 0x00000040,
        VK_ACCESS_COLOR_ATTACHMENT_READ_BIT = 0x00000080,
        VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT = 0x00000100,
        VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_READ_BIT = 0x00000200,
        VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT = 0x00000400,
        VK_ACCESS_TRANSFER_READ_BIT = 0x00000800,
        VK_ACCESS_TRANSFER_WRITE_BIT = 0x00001000,
        VK_ACCESS_HOST_READ_BIT = 0x00002000,
        VK_ACCESS_HOST_WRITE_BIT = 0x00004000,
        VK_ACCESS_MEMORY_READ_BIT = 0x00008000,
        VK_ACCESS_MEMORY_WRITE_BIT = 0x00010000,
      // Provided by VK_EXT_transform_feedback
        VK_ACCESS_TRANSFORM_FEEDBACK_WRITE_BIT_EXT = 0x02000000,
      // Provided by VK_EXT_transform_feedback
        VK_ACCESS_TRANSFORM_FEEDBACK_COUNTER_READ_BIT_EXT = 0x04000000,
      // Provided by VK_EXT_transform_feedback
        VK_ACCESS_TRANSFORM_FEEDBACK_COUNTER_WRITE_BIT_EXT = 0x08000000,
      // Provided by VK_EXT_conditional_rendering
        VK_ACCESS_CONDITIONAL_RENDERING_READ_BIT_EXT = 0x00100000,
      // Provided by VK_EXT_blend_operation_advanced
        VK_ACCESS_COLOR_ATTACHMENT_READ_NONCOHERENT_BIT_EXT = 0x00080000,
      // Provided by VK_KHR_acceleration_structure
        VK_ACCESS_ACCELERATION_STRUCTURE_READ_BIT_KHR = 0x00200000,
      // Provided by VK_KHR_acceleration_structure
        VK_ACCESS_ACCELERATION_STRUCTURE_WRITE_BIT_KHR = 0x00400000,
      // Provided by VK_NV_shading_rate_image
        VK_ACCESS_SHADING_RATE_IMAGE_READ_BIT_NV = 0x00800000,
      // Provided by VK_EXT_fragment_density_map
        VK_ACCESS_FRAGMENT_DENSITY_MAP_READ_BIT_EXT = 0x01000000,
      // Provided by VK_NV_device_generated_commands
        VK_ACCESS_COMMAND_PREPROCESS_READ_BIT_NV = 0x00020000,
      // Provided by VK_NV_device_generated_commands
        VK_ACCESS_COMMAND_PREPROCESS_WRITE_BIT_NV = 0x00040000,
      // Provided by VK_KHR_synchronization2
        VK_ACCESS_NONE_KHR = 0,
      // Provided by VK_NV_ray_tracing
        VK_ACCESS_ACCELERATION_STRUCTURE_READ_BIT_NV = VK_ACCESS_ACCELERATION_STRUCTURE_READ_BIT_KHR,
      // Provided by VK_NV_ray_tracing
        VK_ACCESS_ACCELERATION_STRUCTURE_WRITE_BIT_NV = VK_ACCESS_ACCELERATION_STRUCTURE_WRITE_BIT_KHR,
      // Provided by VK_KHR_fragment_shading_rate
        VK_ACCESS_FRAGMENT_SHADING_RATE_ATTACHMENT_READ_BIT_KHR = VK_ACCESS_SHADING_RATE_IMAGE_READ_BIT_NV,
    } VkAccessFlagBits;

## Description

These values all have the same value/meaning as the equivalently named values for VkAccessFlags2KHR.

- `VK_ACCESS_NONE_KHR` specifies no accesses.

- `VK_ACCESS_INDIRECT_COMMAND_READ_BIT` specifies read access to indirect command data read as part of an indirect build, trace, drawing or dispatch command.

- `VK_ACCESS_INDEX_READ_BIT` specifies read access to an index buffer as part of an indexed drawing command, bound by vkCmdBindIndexBuffer.

- `VK_ACCESS_VERTEX_ATTRIBUTE_READ_BIT` specifies read access to a vertex buffer as part of a drawing command, bound by vkCmdBindVertexBuffers.

- `VK_ACCESS_UNIFORM_READ_BIT` specifies read access to a uniform buffer.

- `VK_ACCESS_INPUT_ATTACHMENT_READ_BIT` specifies read access to an input attachment within a render pass during fragment shading.

- `VK_ACCESS_SHADER_READ_BIT` specifies read access to a storage buffer, physical storage buffer, shader binding table, uniform texel buffer, storage texel buffer, sampled image, or storage image.

- `VK_ACCESS_SHADER_WRITE_BIT` specifies write access to a storage buffer, physical storage buffer, storage texel buffer, or storage image.

- `VK_ACCESS_COLOR_ATTACHMENT_READ_BIT` specifies read access to a color attachment, such as via blending, logic operations, or via certain subpass load operations. It does not include advanced blend operations.

- `VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT` specifies write access to a color, resolve, or depth/stencil resolve attachment during a render pass or via certain subpass load and store operations.

- `VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_READ_BIT` specifies read access to a depth/stencil attachment, via depth or stencil operations or via certain subpass load operations.

- `VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT` specifies write access to a depth/stencil attachment, via depth or stencil operations or via certain subpass load and store operations.

- `VK_ACCESS_TRANSFER_READ_BIT` specifies read access to an image or buffer in a copy operation.

- `VK_ACCESS_TRANSFER_WRITE_BIT` specifies write access to an image or buffer in a clear or copy operation.

- `VK_ACCESS_HOST_READ_BIT` specifies read access by a host operation. Accesses of this type are not performed through a resource, but directly on memory.

- `VK_ACCESS_HOST_WRITE_BIT` specifies write access by a host operation. Accesses of this type are not performed through a resource, but directly on memory.

- `VK_ACCESS_MEMORY_READ_BIT` specifies all read accesses. It is always valid in any access mask, and is treated as equivalent to setting all `READ` access flags that are valid where it is used.

- `VK_ACCESS_MEMORY_WRITE_BIT` specifies all write accesses. It is always valid in any access mask, and is treated as equivalent to setting all `WRITE` access flags that are valid where it is used.

- `VK_ACCESS_CONDITIONAL_RENDERING_READ_BIT_EXT` specifies read access to a predicate as part of conditional rendering.

- `VK_ACCESS_TRANSFORM_FEEDBACK_WRITE_BIT_EXT` specifies write access to a transform feedback buffer made when transform feedback is active.

- `VK_ACCESS_TRANSFORM_FEEDBACK_COUNTER_READ_BIT_EXT` specifies read access to a transform feedback counter buffer which is read when `vkCmdBeginTransformFeedbackEXT` executes.

- `VK_ACCESS_TRANSFORM_FEEDBACK_COUNTER_WRITE_BIT_EXT` specifies write access to a transform feedback counter buffer which is written when `vkCmdEndTransformFeedbackEXT` executes.

- `VK_ACCESS_COMMAND_PREPROCESS_READ_BIT_NV` specifies reads from `VkBuffer` inputs to vkCmdPreprocessGeneratedCommandsNV.

- `VK_ACCESS_COMMAND_PREPROCESS_WRITE_BIT_NV` specifies writes to the `VkBuffer` preprocess outputs in vkCmdPreprocessGeneratedCommandsNV.

- `VK_ACCESS_COLOR_ATTACHMENT_READ_NONCOHERENT_BIT_EXT` is similar to `VK_ACCESS_COLOR_ATTACHMENT_READ_BIT`, but also includes advanced blend operations.

- `VK_ACCESS_FRAGMENT_SHADING_RATE_ATTACHMENT_READ_BIT_KHR` specifies read access to a fragment shading rate attachment or shading rate image during rasterization.

- `VK_ACCESS_ACCELERATION_STRUCTURE_READ_BIT_KHR` specifies read access to an acceleration structure as part of a trace, build, or copy command, or to an acceleration structure scratch buffer as part of a build command.

- `VK_ACCESS_ACCELERATION_STRUCTURE_WRITE_BIT_KHR` specifies write access to an acceleration structure or acceleration structure scratch buffer as part of a build or copy command.

- `VK_ACCESS_FRAGMENT_DENSITY_MAP_READ_BIT_EXT` specifies read access to a fragment density map attachment during dynamic fragment density map operations

Certain access types are only performed by a subset of pipeline stages. Any synchronization command that takes both stage masks and access masks uses both to define the access scopes - only the specified access types performed by the specified stages are included in the access scope. An application must not specify an access flag in a synchronization command if it does not include a pipeline stage in the corresponding stage mask that is able to perform accesses of that type. The following table lists, for each access flag, which pipeline stages can perform that type of access.

Table 1. Supported access types
Access flag | Supported pipeline stages
--- | ---
`VK_ACCESS_INDIRECT_COMMAND_READ_BIT` | `VK_PIPELINE_STAGE_DRAW_INDIRECT_BIT` , `VK_PIPELINE_STAGE_ACCELERATION_STRUCTURE_BUILD_BIT_KHR`
`VK_ACCESS_INDEX_READ_BIT` | `VK_PIPELINE_STAGE_VERTEX_INPUT_BIT`
`VK_ACCESS_VERTEX_ATTRIBUTE_READ_BIT` | `VK_PIPELINE_STAGE_VERTEX_INPUT_BIT`
`VK_ACCESS_UNIFORM_READ_BIT` | `VK_PIPELINE_STAGE_TASK_SHADER_BIT_NV`, `VK_PIPELINE_STAGE_MESH_SHADER_BIT_NV`, `VK_PIPELINE_STAGE_RAY_TRACING_SHADER_BIT_KHR`, `VK_PIPELINE_STAGE_VERTEX_SHADER_BIT`, `VK_PIPELINE_STAGE_TESSELLATION_CONTROL_SHADER_BIT`, `VK_PIPELINE_STAGE_TESSELLATION_EVALUATION_SHADER_BIT`, `VK_PIPELINE_STAGE_GEOMETRY_SHADER_BIT`, `VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT`, or `VK_PIPELINE_STAGE_COMPUTE_SHADER_BIT`
`VK_ACCESS_SHADER_READ_BIT` | `VK_PIPELINE_STAGE_ACCELERATION_STRUCTURE_BUILD_BIT_KHR`, `VK_PIPELINE_STAGE_TASK_SHADER_BIT_NV`, `VK_PIPELINE_STAGE_MESH_SHADER_BIT_NV`, `VK_PIPELINE_STAGE_RAY_TRACING_SHADER_BIT_KHR`, `VK_PIPELINE_STAGE_VERTEX_SHADER_BIT`, `VK_PIPELINE_STAGE_TESSELLATION_CONTROL_SHADER_BIT`, `VK_PIPELINE_STAGE_TESSELLATION_EVALUATION_SHADER_BIT`, `VK_PIPELINE_STAGE_GEOMETRY_SHADER_BIT`, `VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT`, or `VK_PIPELINE_STAGE_COMPUTE_SHADER_BIT`
`VK_ACCESS_SHADER_WRITE_BIT` | `VK_PIPELINE_STAGE_TASK_SHADER_BIT_NV`, `VK_PIPELINE_STAGE_MESH_SHADER_BIT_NV`, `VK_PIPELINE_STAGE_RAY_TRACING_SHADER_BIT_KHR`, `VK_PIPELINE_STAGE_VERTEX_SHADER_BIT`, `VK_PIPELINE_STAGE_TESSELLATION_CONTROL_SHADER_BIT`, `VK_PIPELINE_STAGE_TESSELLATION_EVALUATION_SHADER_BIT`, `VK_PIPELINE_STAGE_GEOMETRY_SHADER_BIT`, `VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT`, or `VK_PIPELINE_STAGE_COMPUTE_SHADER_BIT`
`VK_ACCESS_INPUT_ATTACHMENT_READ_BIT` | `VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT`
`VK_ACCESS_COLOR_ATTACHMENT_READ_BIT` | `VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT`
`VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT` | `VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT`
`VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_READ_BIT` | `VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT`, or `VK_PIPELINE_STAGE_LATE_FRAGMENT_TESTS_BIT`
`VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT` | `VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT`, or `VK_PIPELINE_STAGE_LATE_FRAGMENT_TESTS_BIT`
`VK_ACCESS_TRANSFER_READ_BIT` | `VK_PIPELINE_STAGE_TRANSFER_BIT` or `VK_PIPELINE_STAGE_ACCELERATION_STRUCTURE_BUILD_BIT_KHR`
`VK_ACCESS_TRANSFER_WRITE_BIT` | `VK_PIPELINE_STAGE_TRANSFER_BIT` or `VK_PIPELINE_STAGE_ACCELERATION_STRUCTURE_BUILD_BIT_KHR`
`VK_ACCESS_HOST_READ_BIT` | `VK_PIPELINE_STAGE_HOST_BIT`
`VK_ACCESS_HOST_WRITE_BIT` | `VK_PIPELINE_STAGE_HOST_BIT`
`VK_ACCESS_MEMORY_READ_BIT` | Any
`VK_ACCESS_MEMORY_WRITE_BIT` | Any
`VK_ACCESS_COLOR_ATTACHMENT_READ_NONCOHERENT_BIT_EXT` | `VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT`
`VK_ACCESS_COMMAND_PREPROCESS_READ_BIT_NV` | `VK_PIPELINE_STAGE_COMMAND_PREPROCESS_BIT_NV`
`VK_ACCESS_COMMAND_PREPROCESS_WRITE_BIT_NV` | `VK_PIPELINE_STAGE_COMMAND_PREPROCESS_BIT_NV`
`VK_ACCESS_CONDITIONAL_RENDERING_READ_BIT_EXT` | `VK_PIPELINE_STAGE_CONDITIONAL_RENDERING_BIT_EXT`
`VK_ACCESS_FRAGMENT_SHADING_RATE_ATTACHMENT_READ_BIT_KHR` | `VK_PIPELINE_STAGE_FRAGMENT_SHADING_RATE_ATTACHMENT_BIT_KHR`
`VK_ACCESS_TRANSFORM_FEEDBACK_WRITE_BIT_EXT` | `VK_PIPELINE_STAGE_TRANSFORM_FEEDBACK_BIT_EXT`
`VK_ACCESS_TRANSFORM_FEEDBACK_COUNTER_WRITE_BIT_EXT` | `VK_PIPELINE_STAGE_TRANSFORM_FEEDBACK_BIT_EXT`
`VK_ACCESS_TRANSFORM_FEEDBACK_COUNTER_READ_BIT_EXT` | `VK_PIPELINE_STAGE_TRANSFORM_FEEDBACK_BIT_EXT`, `VK_PIPELINE_STAGE_DRAW_INDIRECT_BIT`
`VK_ACCESS_ACCELERATION_STRUCTURE_READ_BIT_KHR` | `VK_PIPELINE_STAGE_TASK_SHADER_BIT_NV`, `VK_PIPELINE_STAGE_MESH_SHADER_BIT_NV`, `VK_PIPELINE_STAGE_VERTEX_SHADER_BIT`, `VK_PIPELINE_STAGE_TESSELLATION_CONTROL_SHADER_BIT`, `VK_PIPELINE_STAGE_TESSELLATION_EVALUATION_SHADER_BIT`, `VK_PIPELINE_STAGE_GEOMETRY_SHADER_BIT`, `VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT`, `VK_PIPELINE_STAGE_COMPUTE_SHADER_BIT`, `VK_PIPELINE_STAGE_RAY_TRACING_SHADER_BIT_KHR`, or `VK_PIPELINE_STAGE_ACCELERATION_STRUCTURE_BUILD_BIT_KHR`
`VK_ACCESS_ACCELERATION_STRUCTURE_WRITE_BIT_KHR` | `VK_PIPELINE_STAGE_ACCELERATION_STRUCTURE_BUILD_BIT_KHR`
`VK_ACCESS_FRAGMENT_DENSITY_MAP_READ_BIT_EXT` | `VK_PIPELINE_STAGE_FRAGMENT_DENSITY_PROCESS_BIT_EXT`

## See Also

VkAccessFlags

## Document Notes

For more information, see the Vulkan Specification

This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification, not directly.

## Copyright

Copyright 2014-2021 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0