# InstanceCustomIndexKHR(3) Manual Page

## Name

InstanceCustomIndexKHR - Custom index associated with an intersected instance

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## Description

`InstanceCustomIndexKHR`

  A variable decorated with the `InstanceCustomIndexKHR` decoration will contain the application-defined value of the instance that intersects the current ray. This variable contains the value that was specified in VkAccelerationStructureInstanceKHR::`instanceCustomIndex` for the current acceleration structure instance in the lower 24 bits and the upper 8 bits will be zero.

Valid Usage

- VUID-InstanceCustomIndexKHR-InstanceCustomIndexKHR-04251
  The `InstanceCustomIndexKHR` decoration must be used only within the `IntersectionKHR`, `AnyHitKHR`, or `ClosestHitKHR` `Execution` `Model`

- VUID-InstanceCustomIndexKHR-InstanceCustomIndexKHR-04252
  The variable decorated with `InstanceCustomIndexKHR` must be declared using the `Input` `Storage` `Class`

- VUID-InstanceCustomIndexKHR-InstanceCustomIndexKHR-04253
  The variable decorated with `InstanceCustomIndexKHR` must be declared as a scalar 32-bit integer value

## See Also

No cross-references are available

## 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