vkCmdCopyAccelerationStructureToMemoryKHR(3)

# vkCmdCopyAccelerationStructureToMemoryKHR(3) Manual Page

## Name

vkCmdCopyAccelerationStructureToMemoryKHR - Copy an acceleration structure to device memory

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## C Specification

To copy an acceleration structure to device memory call:

    // Provided by VK_KHR_acceleration_structure
    void vkCmdCopyAccelerationStructureToMemoryKHR(
        VkCommandBuffer                             commandBuffer,
        const VkCopyAccelerationStructureToMemoryInfoKHR* pInfo);

## Parameters

- `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.

## Description

Accesses to `pInfo`->`src` must be synchronized with the `VK_PIPELINE_STAGE_ACCELERATION_STRUCTURE_BUILD_BIT_KHR` pipeline stage and an access type of `VK_ACCESS_ACCELERATION_STRUCTURE_READ_BIT_KHR`. Accesses to the buffer indicated by `pInfo`->`dst.deviceAddress` must be synchronized with the `VK_PIPELINE_STAGE_ACCELERATION_STRUCTURE_BUILD_BIT_KHR` pipeline stage and an access type of `VK_ACCESS_TRANSFER_WRITE_BIT`.

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.

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`::`size`

- 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. The serialized data is written to the buffer (or read from the buffer) according to the host endianness.

Valid Usage

- VUID-vkCmdCopyAccelerationStructureToMemoryKHR-pInfo-03739
  `pInfo`->`dst.deviceAddress` must be a valid device address for a buffer bound to device memory.

- VUID-vkCmdCopyAccelerationStructureToMemoryKHR-pInfo-03740
  `pInfo`->`dst.deviceAddress` must be aligned to `256` bytes

- VUID-vkCmdCopyAccelerationStructureToMemoryKHR-pInfo-03741
  If the buffer pointed to by `pInfo`->`dst.deviceAddress` is non-sparse then it must be bound completely and contiguously to a single VkDeviceMemory object

- VUID-vkCmdCopyAccelerationStructureToMemoryKHR-None-03559
  The `buffer` used to create `pInfo`->`src` must be bound to device memory

Valid Usage (Implicit)

- VUID-vkCmdCopyAccelerationStructureToMemoryKHR-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdCopyAccelerationStructureToMemoryKHR-pInfo-parameter
  `pInfo` must be a valid pointer to a valid VkCopyAccelerationStructureToMemoryInfoKHR structure

- VUID-vkCmdCopyAccelerationStructureToMemoryKHR-commandBuffer-recording
  `commandBuffer` must be in the recording state

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

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

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 | 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 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0