VK_AMD_texture_gather_bias_lod(3)

# VK_AMD_texture_gather_bias_lod(3) Manual Page

## Name

VK_AMD_texture_gather_bias_lod - device extension

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## Registered Extension Number

42

## Revision

1

## Extension and Version Dependencies

- Requires Vulkan 1.0

- Requires `VK_KHR_get_physical_device_properties2`

### Other Extension Metadata

Last Modified Date

  2017-03-21

IP Status

  No known IP claims.

Interactions and External Dependencies

  - Requires the `SPV_AMD_texture_gather_bias_lod` SPIR-V extension.

Contributors

  - Dominik Witczak, AMD

  - Daniel Rakos, AMD

  - Graham Sellers, AMD

  - Matthaeus G. Chajdas, AMD

  - Qun Lin, AMD

  - Rex Xu, AMD

  - Timothy Lottes, AMD

### Description

This extension adds two related features.

Firstly, support for the following SPIR-V extension in Vulkan is added:

- `SPV_AMD_texture_gather_bias_lod`

Secondly, the extension allows the application to query which formats can be used together with the new function prototypes introduced by the SPIR-V extension.

### New Structures

- Extending VkImageFormatProperties2:

  - VkTextureLODGatherFormatPropertiesAMD

### New Enum Constants

- `VK_AMD_TEXTURE_GATHER_BIAS_LOD_EXTENSION_NAME`

- `VK_AMD_TEXTURE_GATHER_BIAS_LOD_SPEC_VERSION`

- Extending VkStructureType:

  - `VK_STRUCTURE_TYPE_TEXTURE_LOD_GATHER_FORMAT_PROPERTIES_AMD`

### New SPIR-V Capabilities

- `ImageGatherBiasLodAMD`

### Examples

    struct VkTextureLODGatherFormatPropertiesAMD
    {
        VkStructureType sType;
        const void*     pNext;
        VkBool32        supportsTextureGatherLODBiasAMD;
    };

    // ----------------------------------------------------------------------------------------
    // How to detect if an image format can be used with the new function prototypes.
    VkPhysicalDeviceImageFormatInfo2   formatInfo;
    VkImageFormatProperties2           formatProps;
    VkTextureLODGatherFormatPropertiesAMD textureLODGatherSupport;

    textureLODGatherSupport.sType = VK_STRUCTURE_TYPE_TEXTURE_LOD_GATHER_FORMAT_PROPERTIES_AMD;
    textureLODGatherSupport.pNext = nullptr;

    formatInfo.sType  = VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_IMAGE_FORMAT_INFO_2;
    formatInfo.pNext  = nullptr;
    formatInfo.format = ...;
    formatInfo.type   = ...;
    formatInfo.tiling = ...;
    formatInfo.usage  = ...;
    formatInfo.flags  = ...;

    formatProps.sType = VK_STRUCTURE_TYPE_IMAGE_FORMAT_PROPERTIES_2;
    formatProps.pNext = &textureLODGatherSupport;

    vkGetPhysicalDeviceImageFormatProperties2(physical_device, &formatInfo, &formatProps);

    if (textureLODGatherSupport.supportsTextureGatherLODBiasAMD == VK_TRUE)
    {
        // physical device supports SPV_AMD_texture_gather_bias_lod for the specified
        // format configuration.
    }
    else
    {
        // physical device does not support SPV_AMD_texture_gather_bias_lod for the
        // specified format configuration.
    }

### Version History

- Revision 1, 2017-03-21 (Dominik Witczak)

  - Initial draft

## See Also

VkTextureLODGatherFormatPropertiesAMD

## Document Notes

For more information, see the Vulkan Specification

This page is a generated document. Fixes and changes should be made to the generator scripts, not directly.

## Copyright

Copyright (c) 2014-2020 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0