# VkDescriptorMappingSourceIndirectIndexEXT(3) Manual Page

## Name

VkDescriptorMappingSourceIndirectIndexEXT - Structure specifying mapping resources to a heap index in indirect data

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## C Specification

The `VkDescriptorMappingSourceIndirectIndexEXT` structure is defined as:

    // Provided by VK_EXT_descriptor_heap
    typedef struct VkDescriptorMappingSourceIndirectIndexEXT {
        uint32_t                      heapOffset;
        uint32_t                      pushOffset;
        uint32_t                      addressOffset;
        uint32_t                      heapIndexStride;
        uint32_t                      heapArrayStride;
        const VkSamplerCreateInfo*    pEmbeddedSampler;
        VkBool32                      useCombinedImageSamplerIndex;
        uint32_t                      samplerHeapOffset;
        uint32_t                      samplerPushOffset;
        uint32_t                      samplerAddressOffset;
        uint32_t                      samplerHeapIndexStride;
        uint32_t                      samplerHeapArrayStride;
    } VkDescriptorMappingSourceIndirectIndexEXT;

## Members

- `heapOffset` is a constant byte offset added to the heap address for the mapped resource or sampler.

- `pushOffset` is an offset into push data where an the indirect address will be.

- `addressOffset` is an index into the address in push data where an index into the heap for the mapped resource will be retrieved.

- `heapIndexStride` is a constant byte stride that multiplies the index in indirect data.

- `heapArrayStride` is a constant byte stride that multiplies the shader binding and array index.

- `pEmbeddedSampler` is an optional VkSamplerCreateInfo structure specifying a sampler to embed into the shader, in place of looking the sampler up in a heap.

- `useCombinedImageSamplerIndex` specifies whether the generated index value will be decoded as two packed indices if the mapped resource is an `OpTypeSampledImage`.

- `samplerHeapOffset` is used only when mapping a combined image sampler, used in place of `heapOffset` to retrieve the sampler.

- `samplerPushOffset` is used only when mapping a combined image sampler, used in place of `pushOffset` to retrieve the sampler.

- `samplerAddressOffset` is used only when mapping a combined image sampler, used in place of `addressOffset` to retrieve the sampler.

- `samplerHeapIndexStride` is used only when mapping a combined image sampler, used in place of `heapIndexStride` to retrieve the sampler.

- `samplerHeapArrayStride` is used only when mapping a combined image sampler, used in place of `heapArrayStride` to retrieve the sampler.

## Description

Resources using this mapping will be backed by a descriptor in the heap, at an offset calculated as

  uint32_t *indirectAddress = ((VkDeviceAddress*)pPushData)[pushOffset/8]

  indirectIndex = indirectAddress[(addressOffset / 4)]

  shaderIndex = (Binding - firstBinding) + arrayIndex

  offset = heapOffset + (indirectIndex × heapIndexStride) + (shaderIndex × heapArrayStride)

where Binding is the binding value in the shader, arrayIndex is the index into the array if the shader binding is declared as an array, and pPushData is the total set of push data specified by vkCmdPushDataEXT. The value of the address in push data must be a multiple of 4. Index reads through indirectAddress are performed as non-volatile uniform buffer reads, and can be synchronized using VK_ACCESS_2_UNIFORM_READ_BIT. The value in memory must remain static while any shader invocation using this mapping is in flight to avoid a data race.

If the mapped resource is a `OpTypeSampledImage`, offset is instead calculated for the sampler as

  uint32_t *samplerIndirectAddress = ((VkDeviceAddress*)pPushData)[samplerPushOffset/8]

  samplerIndirectIndex = samplerIndirectAddress[(samplerAddressOffset / 4)]

  offset = samplerHeapOffset + (samplerIndirectIndex × samplerHeapIndexStride) + (shaderIndex × samplerHeapArrayStride)

If `useCombinedImageSamplerIndex` is VK_TRUE, and the mapped resource is a `OpTypeSampledImage`, indirectIndex and samplerIndirectIndex in the above equations are instead calculated as

  indirectIndex = indirectAddress[addressOffset/4] & 0xFFFFF

  samplerIndirectIndex = indirectAddress[addressOffset/4] >> 20) & 0xFFF

If the mapped resource is a `OpTypeSampler` or `OpTypeSampledImage`, and `pEmbeddedSampler` is not `NULL`, the specified embedded sampler will be used rather than accessing the sampler heap.

Valid Usage

- VUID-VkDescriptorMappingSourceIndirectIndexEXT-pushOffset-11260
  `pushOffset` must be a multiple of 8

- VUID-VkDescriptorMappingSourceIndirectIndexEXT-pushOffset-11261
  `pushOffset` must be less than or equal to `maxPushDataSize` - 8

- VUID-VkDescriptorMappingSourceIndirectIndexEXT-addressOffset-11262
  `addressOffset` must be a multiple of 4

- VUID-VkDescriptorMappingSourceIndirectIndexEXT-pEmbeddedSampler-11447
  If `pEmbeddedSampler` is a valid pointer to a VkSamplerCreateInfo, its `borderColor` must not be VK_BORDER_COLOR_FLOAT_CUSTOM_EXT or VK_BORDER_COLOR_INT_CUSTOM_EXT

- VUID-VkDescriptorMappingSourceIndirectIndexEXT-pEmbeddedSampler-11403
  If `pEmbeddedSampler` is a valid pointer to a VkSamplerCreateInfo, and there is a VkDebugUtilsObjectNameInfoEXT structure in its `pNext` chain, its `objectType` must be VK_OBJECT_TYPE_UNKNOWN

Valid Usage (Implicit)

- VUID-VkDescriptorMappingSourceIndirectIndexEXT-pEmbeddedSampler-parameter
  If `pEmbeddedSampler` is not `NULL`, `pEmbeddedSampler` must be a valid pointer to a valid VkSamplerCreateInfo structure

## See Also

VK_EXT_descriptor_heap, VkBool32, VkDescriptorMappingSourceDataEXT, VkSamplerCreateInfo

## 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 2014-2026 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0