# vkCmdCopyAccelerationStructureToMemoryKHR(3) Manual Page

## Name

vkCmdCopyAccelerationStructureToMemoryKHR - Copy an acceleration structure to device memory

## C Specification

To copy an acceleration structure to device memory call:

    void vkCmdCopyAccelerationStructureToMemoryKHR(
        VkCommandBuffer                             commandBuffer,
        const VkCopyAccelerationStructureToMemoryInfoKHR* pInfo);

## Parameters

This command produces the same results as vkCopyAccelerationStructureToMemoryKHR, but writes its result to a device address, and is executed on the device rather than the host. The output may not necessarily be bit-for-bit identical, but it can be equally used by either vkCmdCopyMemoryToAccelerationStructureKHR or vkCopyMemoryToAccelerationStructureKHR.

## Description

- `commandBuffer` is the command buffer into which the command will be recorded.

- `pInfo` is an a pointer to a VkCopyAccelerationStructureToMemoryInfoKHR structure defining the copy operation.

The defined header structure for the serialized data consists of:

- `VK_UUID_SIZE` bytes of data matching `VkPhysicalDeviceIDProperties`::`driverUUID`

- `VK_UUID_SIZE` bytes of data identifying the compatibility for comparison using vkGetDeviceAccelerationStructureCompatibilityKHR

- A 64-bit integer of the total size matching the value queried using `VK_QUERY_TYPE_ACCELERATION_STRUCTURE_SERIALIZATION_SIZE_KHR`

- A 64-bit integer of the deserialized size to be passed in to `VkAccelerationStructureCreateInfoKHR`::`compactedSize`

- A 64-bit integer of the count of the number of acceleration structure handles following. This will be zero for a bottom-level acceleration structure.

The corresponding handles matching the values returned by vkGetAccelerationStructureDeviceAddressKHR or vkGetAccelerationStructureHandleNV are tightly packed in the buffer following the count. The application is expected to store a mapping between those handles and the original application-generated bottom-level acceleration structures to provide when deserializing.

Valid Usage

- All `VkDeviceOrHostAddressConstKHR` referenced by this command must contain valid device addresses.

- All `VkAccelerationStructureKHR` objects referenced by this command must be bound to device memory.

- The VkDeferredOperationInfoKHR structure must not be included in the `pNext` chain of the VkCopyAccelerationStructureToMemoryInfoKHR structure.

- [[VUID-{refpage}-mode-03412]] `mode` must be `VK_COPY_ACCELERATION_STRUCTURE_MODE_SERIALIZE_KHR`

Valid Usage (Implicit)

- `commandBuffer` must be a valid VkCommandBuffer handle

- `pInfo` must be a valid pointer to a valid VkCopyAccelerationStructureToMemoryInfoKHR structure

- `commandBuffer` must be in the recording state

- The `VkCommandPool` that `commandBuffer` was allocated from must support compute operations

- This command must only be called outside of a render pass instance

Host Synchronization

- 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 | Outside | Compute |

## See Also

VkCommandBuffer, VkCopyAccelerationStructureToMemoryInfoKHR

## 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 (c) 2014-2020 Khronos Group. This work is licensed under a Creative Commons Attribution 4.0 International License.