Vulkan-Docs/appendices/VK_EXT_vertex_attribute_divisor.txt
Jon Leech 279452463a Change log for November 12, 2018 Vulkan 1.1.92 spec update:
* Update release number to 92.

Public Issues:

  * Move and modify valid usage statements dealing with pname:aspectMask in
    flink:vkCmdClearColorImage, flink:vkCmdClearDepthStencilImage, and
    slink:VkClearAttachment, so they are in places where all necessary
    information is available (public issue 529).
  * Fix math markup in <<textures-texel-anisotropic-filtering, Texel
    Anisotropic Filtering>> (public pull request 840).
  * Fix misspellings (public pull request 845).

Internal Issues:

  * Add installation instructions and a Makefile "`chunked`" target for
    chunked HTML generation (internal issue 1352).
  * Fix pipeline mesh diagram style; also fix a minor bug in the classic
    pipeline diagram where vertex/index buffers wrongly fed into the vertex
    shader (internal issue 1436).
  * Make asciidoctor ERROR output raise an error, and don't suppress
    executed command output from CI make invocation (internal issue 1454).
  * Minor typo fixes and clarifications for `VK_NV_raytracing`.
  * Cleanup extension-specific properties
  ** Remove duplicated documentation for pname:maxDiscardRectangles,
     pname:pointClippingBehavior, and pname:maxVertexAttribDivisor (they
     shouldn't be documented with the other members of
     slink:VkPhysicalDeviceLimits at all).
  ** Remove duplicate anchor for pname:maxVertexAttribDivisor
  ** Consistently document stext:VkPhysicalDevice<Extension>PropertiesKHR
  *** Always document pname:sType/pname:pNext (was inconsistent before)
  *** Always mention chaining to slink:VkPhysicalDeviceProperties2 (and not
      as slink:VkPhysicalDeviceProperties2KHR)
  *** Always include Valid Usage statements last
  * Update Makefile 'checklinks' target and associated scripts, and fix
    markup problems identified by checkLinks.py, so that we can rely on the
    checklinks script as part of Gitlab CI.
2018-11-12 04:40:40 -08:00

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include::meta/VK_EXT_vertex_attribute_divisor.txt[]
*Last Modified Date*::
2018-08-03
*IP Status*::
No known IP claims.
*Contributors*::
- Vikram Kushwaha, NVIDIA
- Jason Ekstrand, Intel
This extension allows instance-rate vertex attributes to be repeated for
certain number of instances instead of advancing for every instance when
instanced rendering is enabled.
=== New Object Types
None.
=== New Enum Constants
Extending elink:VkStructureType:
** ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_VERTEX_ATTRIBUTE_DIVISOR_PROPERTIES_EXT
** ename:VK_STRUCTURE_TYPE_PIPELINE_VERTEX_INPUT_DIVISOR_STATE_CREATE_INFO_EXT
** ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_VERTEX_ATTRIBUTE_DIVISOR_FEATURES_EXT
=== New Enums
None.
=== New Structures
* Extending slink:VkPipelineVertexInputStateCreateInfo:
** slink:VkPipelineVertexInputDivisorStateCreateInfoEXT
* slink:VkPhysicalDeviceVertexAttributeDivisorPropertiesEXT
* slink:VkVertexInputBindingDivisorDescriptionEXT
* Extending slink:VkPhysicalDeviceFeatures2:
** slink:VkPhysicalDeviceVertexAttributeDivisorFeaturesEXT
=== New Functions
None.
=== Issues
1) What is the effect of a non-zero value for pname:firstInstance?
*RESOLVED*: The Vulkan API should follow the OpenGL convention and offset
attribute fetching by pname:firstInstance while computing vertex attribute
offsets.
2) Should zero be an allowed divisor?
*RESOLVED*: Yes.
A zero divisor means the vertex attribute is repeated for all instances.
=== Examples
To create a vertex binding such that the first binding uses instanced
rendering and the same attribute is used for every 4 draw instances, an
application could use the following set of structures:
[source,c++]
----------------------------------------
const VkVertexInputBindingDivisorDescriptionEXT divisorDesc =
{
0,
4
};
const VkPipelineVertexInputDivisorStateCreateInfoEXT divisorInfo =
{
VK_STRUCTURE_TYPE_PIPELINE_VERTEX_INPUT_DIVISOR_STATE_CREATE_INFO_EXT, // sType
NULL, // pNext
1, // vertexBindingDivisorCount
&divisorDesc // pVertexBindingDivisors
}
const VkVertexInputBindingDescription binding =
{
0, // binding
sizeof(Vertex), // stride
VK_VERTEX_INPUT_RATE_INSTANCE // inputRate
};
const VkPipelineVertexInputStateCreateInfo viInfo =
{
VK_STRUCTURE_TYPE_PIPELINE_VERTEX_INPUT_CREATE_INFO, // sType
&divisorInfo, // pNext
...
};
//...
----------------------------------------
=== Version History
* Revision 1, 2017-12-04 (Vikram Kushwaha)
- First Version
* Revision 2, 2018-07-16 (Jason Ekstrand)
- Adjust the interaction between pname:divisor and pname:firstInstance
to match the OpenGL convention.
- Disallow divisors of zero.
* Revision 3, 2018-08-03 (Vikram Kushwaha)
- Allow a zero divisor.
- Add a physical device features structure to query/enable this feature.