vkGetDescriptorSetLayoutBindingOffsetEXT(3)

# vkGetDescriptorSetLayoutBindingOffsetEXT(3) Manual Page

## Name

vkGetDescriptorSetLayoutBindingOffsetEXT - Get the offset of a binding within a descriptor set layout

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## C Specification

To get the offset of a binding within a descriptor set layout in memory, call:

    // Provided by VK_EXT_descriptor_buffer
    void vkGetDescriptorSetLayoutBindingOffsetEXT(
        VkDevice                                    device,
        VkDescriptorSetLayout                       layout,
        uint32_t                                    binding,
        VkDeviceSize*                               pOffset);

## Parameters

- `device` is the logical device that gets the offset.

- `layout` is the descriptor set layout being queried.

- `binding` is the binding number being queried.

- `pOffset` is a pointer to VkDeviceSize where the byte offset of the binding will be written.

## Description

Each binding in a descriptor set layout is assigned an offset in memory by the implementation. When a shader accesses a resource with that binding, it will access the bound descriptor buffer from that offset to look for its descriptor. This command provides an application with that offset, so that descriptors can be placed in the correct locations. The precise location accessed by a shader for a given descriptor is as follows:

  location = bufferAddress + setOffset + descriptorOffset + (arrayElement × descriptorSize)

where bufferAddress and setOffset are the base address and offset for the identified descriptor set as specified by vkCmdBindDescriptorBuffersEXT and vkCmdSetDescriptorBufferOffsetsEXT, descriptorOffset is the offset for the binding returned by this command, arrayElement is the index into the array specified in the shader, and descriptorSize is the size of the relevant descriptor as obtained from VkPhysicalDeviceDescriptorBufferPropertiesEXT. Applications are responsible for placing valid descriptors at the expected location in order for a shader to access it. The overall offset added to bufferAddress to calculate location must be less than VkPhysicalDeviceDescriptorBufferPropertiesEXT::`maxSamplerDescriptorBufferRange` for samplers and VkPhysicalDeviceDescriptorBufferPropertiesEXT::`maxResourceDescriptorBufferRange` for resources.

If any `binding` in `layout` is `VK_DESCRIPTOR_BINDING_VARIABLE_DESCRIPTOR_COUNT_BIT`, that `binding` must have the largest offset of any `binding`.

A descriptor `binding` with type `VK_DESCRIPTOR_TYPE_MUTABLE_VALVE` can be used. Any potential types in VkMutableDescriptorTypeCreateInfoVALVE::`pDescriptorTypes` for `binding` share the same offset. If the size of the mutable descriptor is larger than the size of a concrete descriptor type being accessed, the padding area is ignored by the implementation.

Valid Usage

- VUID-vkGetDescriptorSetLayoutBindingOffsetEXT-None-08013
  The `descriptorBuffer` feature must be enabled

- VUID-vkGetDescriptorSetLayoutBindingOffsetEXT-layout-08014
  `layout` must have been created with the `VK_DESCRIPTOR_SET_LAYOUT_CREATE_DESCRIPTOR_BUFFER_BIT_EXT` flag set

Valid Usage (Implicit)

- VUID-vkGetDescriptorSetLayoutBindingOffsetEXT-device-parameter
  `device` must be a valid VkDevice handle

- VUID-vkGetDescriptorSetLayoutBindingOffsetEXT-layout-parameter
  `layout` must be a valid VkDescriptorSetLayout handle

- VUID-vkGetDescriptorSetLayoutBindingOffsetEXT-pOffset-parameter
  `pOffset` must be a valid pointer to a VkDeviceSize value

- VUID-vkGetDescriptorSetLayoutBindingOffsetEXT-layout-parent
  `layout` must have been created, allocated, or retrieved from `device`

## See Also

VK_EXT_descriptor_buffer, VkDescriptorSetLayout, VkDevice, VkDeviceSize

## 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 2014-2024 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0