5.3. Command Buffer Recording

To begin recording a command buffer, call:

VkResult vkBeginCommandBuffer(
    VkCommandBuffer                             commandBuffer,
    const VkCommandBufferBeginInfo*             pBeginInfo);

commandBuffer is the handle of the command buffer which is to be put in the recording state.
pBeginInfo is an instance of the VkCommandBufferBeginInfo structure, which defines additional information about how the command buffer begins recording.

Valid Usage

commandBuffer must be a valid VkCommandBuffer handle
pBeginInfo must be a pointer to a valid VkCommandBufferBeginInfo structure
commandBuffer must not be in the recording state
commandBuffer must not currently be pending execution
If commandBuffer was allocated from a VkCommandPool which did not have the VK_COMMAND_POOL_CREATE_RESET_COMMAND_BUFFER_BIT flag set, commandBuffer must be in the initial state.
If commandBuffer is a secondary command buffer, the pInheritanceInfo member of pBeginInfo must be a valid VkCommandBufferInheritanceInfo structure
If commandBuffer is a secondary command buffer and either the occlusionQueryEnable member of the pInheritanceInfo member of pBeginInfo is VK_FALSE, or the precise occlusion queries feature is not enabled, the queryFlags member of the pInheritanceInfo member pBeginInfo must not contain VK_QUERY_CONTROL_PRECISE_BIT

The VkCommandBufferBeginInfo structure is defined as:

typedef struct VkCommandBufferBeginInfo {
    VkStructureType                          sType;
    const void*                              pNext;
    VkCommandBufferUsageFlags                flags;
    const VkCommandBufferInheritanceInfo*    pInheritanceInfo;
} VkCommandBufferBeginInfo;

sType is the type of this structure.
pNext is NULL or a pointer to an extension-specific structure.
flags is a bitmask indicating usage behavior for the command buffer. Bits which can be set include:
```
typedef enum VkCommandBufferUsageFlagBits {
    VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT = 0x00000001,
    VK_COMMAND_BUFFER_USAGE_RENDER_PASS_CONTINUE_BIT = 0x00000002,
    VK_COMMAND_BUFFER_USAGE_SIMULTANEOUS_USE_BIT = 0x00000004,
} VkCommandBufferUsageFlagBits;
```
- VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT indicates that each recording of the command buffer will only be submitted once, and the command buffer will be reset and recorded again between each submission.
- VK_COMMAND_BUFFER_USAGE_RENDER_PASS_CONTINUE_BIT indicates that a secondary command buffer is considered to be entirely inside a render pass. If this is a primary command buffer, then this bit is ignored.
- Setting VK_COMMAND_BUFFER_USAGE_SIMULTANEOUS_USE_BIT allows the command buffer to be resubmitted to a queue or recorded into a primary command buffer while it is pending execution.
pInheritanceInfo is a pointer to a VkCommandBufferInheritanceInfo structure, which is used if commandBuffer is a secondary command buffer. If this is a primary command buffer, then this value is ignored.

Valid Usage

sType must be VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO
pNext must be NULL
flags must be a valid combination of VkCommandBufferUsageFlagBits values
If flags contains VK_COMMAND_BUFFER_USAGE_RENDER_PASS_CONTINUE_BIT, the renderPass member of pInheritanceInfo must be a valid VkRenderPass
If flags contains VK_COMMAND_BUFFER_USAGE_RENDER_PASS_CONTINUE_BIT, the subpass member of pInheritanceInfo must be a valid subpass index within the renderPass member of pInheritanceInfo
If flags contains VK_COMMAND_BUFFER_USAGE_RENDER_PASS_CONTINUE_BIT, the framebuffer member of pInheritanceInfo must be either VK_NULL_HANDLE, or a valid VkFramebuffer that is compatible with the renderPass member of pInheritanceInfo

If the command buffer is a secondary command buffer, then the VkCommandBufferInheritanceInfo structure defines any state that will be inherited from the primary command buffer:

typedef struct VkCommandBufferInheritanceInfo {
    VkStructureType                  sType;
    const void*                      pNext;
    VkRenderPass                     renderPass;
    uint32_t                         subpass;
    VkFramebuffer                    framebuffer;
    VkBool32                         occlusionQueryEnable;
    VkQueryControlFlags              queryFlags;
    VkQueryPipelineStatisticFlags    pipelineStatistics;
} VkCommandBufferInheritanceInfo;

renderPass is a VkRenderPass object defining which render passes the VkCommandBuffer will be compatible with and can be executed within. If the VkCommandBuffer will not be executed within a render pass instance, renderPass is ignored.
subpass is the index of the subpass within renderPass that the VkCommandBuffer will be executed within. If the VkCommandBuffer will not be executed within a render pass instance, subpass is ignored.
framebuffer optionally refers to the VkFramebuffer object that the VkCommandBuffer will be rendering to if it is executed within a render pass instance. It can be VK_NULL_HANDLE if the framebuffer is not known, or if the VkCommandBuffer will not be executed within a render pass instance.
Note
Specifying the exact framebuffer that the secondary command buffer will be executed with may result in better performance at command buffer execution time.
occlusionQueryEnable indicates whether the command buffer can be executed while an occlusion query is active in the primary command buffer. If this is VK_TRUE, then this command buffer can be executed whether the primary command buffer has an occlusion query active or not. If this is VK_FALSE, then the primary command buffer must not have an occlusion query active.
queryFlags indicates the query flags that can be used by an active occlusion query in the primary command buffer when this secondary command buffer is executed. If this value includes the VK_QUERY_CONTROL_PRECISE_BIT bit, then the active query can return boolean results or actual sample counts. If this bit is not set, then the active query must not use the VK_QUERY_CONTROL_PRECISE_BIT bit. If this is a primary command buffer, then this value is ignored.
pipelineStatistics indicates the set of pipeline statistics that can be counted by an active query in the primary command buffer when this secondary command buffer is executed. If this value includes a given bit, then this command buffer can be executed whether the primary command buffer has a pipeline statistics query active that includes this bit or not. If this value excludes a given bit, then the active pipeline statistics query must not be from a query pool that counts that statistic.

Valid Usage

sType must be VK_STRUCTURE_TYPE_COMMAND_BUFFER_INHERITANCE_INFO
pNext must be NULL
Both of framebuffer, and renderPass that are valid handles must have been created, allocated, or retrieved from the same VkDevice
If the inherited queries feature is not enabled, occlusionQueryEnable must be VK_FALSE
If the inherited queries feature is enabled, queryFlags must be a valid combination of VkQueryControlFlagBits values
If the pipeline statistics queries feature is not enabled, pipelineStatistics must be 0

A primary command buffer is considered to be pending execution from the time it is submitted via vkQueueSubmit until that submission completes.

A secondary command buffer is considered to be pending execution from the time its execution is recorded into a primary buffer (via vkCmdExecuteCommands) until the final time that primary buffer’s submission to a queue completes. If, after the primary buffer completes, the secondary command buffer is recorded to execute on a different primary buffer, the first primary buffer must not be resubmitted until after it is reset with vkResetCommandBuffer unless the secondary command buffer was recorded with VK_COMMAND_BUFFER_USAGE_SIMULTANEOUS_USE_BIT.

If VK_COMMAND_BUFFER_USAGE_SIMULTANEOUS_USE_BIT is not set on a secondary command buffer, that command buffer must not be used more than once in a given primary command buffer. Furthermore, if a secondary command buffer without VK_COMMAND_BUFFER_USAGE_SIMULTANEOUS_USE_BIT set is recorded to execute in a primary command buffer with VK_COMMAND_BUFFER_USAGE_SIMULTANEOUS_USE_BIT set, the primary command buffer must not be pending execution more than once at a time.

	Note
	On some implementations, not using the `VK_COMMAND_BUFFER_USAGE_SIMULTANEOUS_USE_BIT` bit enables command buffers to be patched in-place if needed, rather than creating a copy of the command buffer.

If a command buffer is in the executable state and the command buffer was allocated from a command pool with the VK_COMMAND_POOL_CREATE_RESET_COMMAND_BUFFER_BIT flag set, then vkBeginCommandBuffer implicitly resets the command buffer, behaving as if vkResetCommandBuffer had been called with VK_COMMAND_BUFFER_RESET_RELEASE_RESOURCES_BIT not set. It then puts the command buffer in the recording state.

Once recording starts, an application records a sequence of commands (vkCmd*) to set state in the command buffer, draw, dispatch, and other commands.

To complete recording of a command buffer, call:

VkResult vkEndCommandBuffer(
    VkCommandBuffer                             commandBuffer);

commandBuffer is the command buffer to complete recording. The command buffer must have been in the recording state, and is moved to the executable state.

If there was an error during recording, the application will be notified by an unsuccessful return code returned by vkEndCommandBuffer. If the application wishes to further use the command buffer, the command buffer must be reset.

When a command buffer is in the executable state, it can be submitted to a queue for execution.

	Note
	Specifying the exact framebuffer that the secondary command buffer will be executed with may result in better performance at command buffer execution time.