1  include::meta/VK_AMD_texture_gather_bias_lod.txt[]
  2  
  3  *Last Modified Date*::
  4      2017-03-21
  5  *IP Status*::
  6      No known IP claims.
  7  *Interactions and External Dependencies*::
  8    - Requires the
  9      https://www.khronos.org/registry/spir-v/extensions/AMD/SPV_AMD_texture_gather_bias_lod.html[`SPV_AMD_texture_gather_bias_lod`]
 10      SPIR-V extension.
 11  *Contributors*::
 12    - Dominik Witczak, AMD
 13    - Daniel Rakos, AMD
 14    - Graham Sellers, AMD
 15    - Matthaeus G. Chajdas, AMD
 16    - Qun Lin, AMD
 17    - Rex Xu, AMD
 18    - Timothy Lottes, AMD
 19  
 20  This extension adds two related features.
 21  
 22  Firstly, support for the following SPIR-V extension in Vulkan is added:
 23  
 24    * `SPV_AMD_texture_gather_bias_lod`
 25  
 26  Secondly, the extension allows the application to query which formats can be
 27  used together with the new function prototypes introduced by the SPIR-V
 28  extension.
 29  
 30  === New Object Types
 31  
 32  None.
 33  
 34  === New Enum Constants
 35  
 36    * Extending elink:VkStructureType:
 37    ** ename:VK_STRUCTURE_TYPE_TEXTURE_LOD_GATHER_FORMAT_PROPERTIES_AMD
 38  
 39  === New Enums
 40  
 41  None.
 42  
 43  === New SPIR-V Capabilities
 44  
 45    * <<spirvenv-capabilities-table-imagegatherbiaslodamd,code:ImageGatherBiasLodAMD>>
 46  
 47  === New Structures
 48  
 49    * slink:VkTextureLODGatherFormatPropertiesAMD
 50  
 51  === New Functions
 52  
 53  None.
 54  
 55  === Examples
 56  
 57  [source,c++]
 58  --------------------------------------
 59  
 60  struct VkTextureLODGatherFormatPropertiesAMD
 61  {
 62      VkStructureType sType;
 63      const void*     pNext;
 64      VkBool32        supportsTextureGatherLODBiasAMD;
 65  };
 66  
 67  // ----------------------------------------------------------------------------------------
 68  // How to detect if an image format can be used with the new function prototypes.
 69  VkPhysicalDeviceImageFormatInfo2   formatInfo;
 70  VkImageFormatProperties2           formatProps;
 71  VkTextureLODGatherFormatPropertiesAMD textureLODGatherSupport;
 72  
 73  textureLODGatherSupport.sType = VK_STRUCTURE_TYPE_TEXTURE_LOD_GATHER_FORMAT_PROPERTIES_AMD;
 74  textureLODGatherSupport.pNext = nullptr;
 75  
 76  formatInfo.sType  = VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_IMAGE_FORMAT_INFO_2;
 77  formatInfo.pNext  = nullptr;
 78  formatInfo.format = ...;
 79  formatInfo.type   = ...;
 80  formatInfo.tiling = ...;
 81  formatInfo.usage  = ...;
 82  formatInfo.flags  = ...;
 83  
 84  formatProps.sType = VK_STRUCTURE_TYPE_IMAGE_FORMAT_PROPERTIES_2;
 85  formatProps.pNext = &textureLODGatherSupport;
 86  
 87  vkGetPhysicalDeviceImageFormatProperties2(physical_device, &formatInfo, &formatProps);
 88  
 89  if (textureLODGatherSupport.supportsTextureGatherLODBiasAMD == VK_TRUE)
 90  {
 91      // physical device supports SPV_AMD_texture_gather_bias_lod for the specified
 92      // format configuration.
 93  }
 94  else
 95  {
 96      // physical device does not support SPV_AMD_texture_gather_bias_lod for the
 97      // specified format configuration.
 98  }
 99  --------------------------------------
100  
101  === Version History
102  
103    * Revision 1, 2017-03-21 (Dominik Witczak)
104      - Initial draft