Name

VK_EXT_vertex_attribute_divisor - device extension

VK_EXT_vertex_attribute_divisor

Name String

VK_EXT_vertex_attribute_divisor

Extension Type

Device extension

Registered Extension Number

191

Revision

3

Extension and Version Dependencies

• Requires Vulkan 1.0
• Requires VK_KHR_get_physical_device_properties2

Contact

• Vikram Kushwaha https://github.com/KhronosGroup/Vulkan-Docs/issues/new?title=VK_EXT_vertex_attribute_divisor:%20&body=@vkushwaha%20

Other Extension Metadata

Last Modified Date

2018-08-03

IP Status

No known IP claims.

Contributors

• Vikram Kushwaha, NVIDIA
• Jason Ekstrand, Intel

Description

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 Structures

• VertexInputBindingDivisorDescriptionEXT

• Extending PhysicalDeviceFeatures2, DeviceCreateInfo:

  • PhysicalDeviceVertexAttributeDivisorFeaturesEXT

• Extending PhysicalDeviceProperties2:

  • PhysicalDeviceVertexAttributeDivisorPropertiesEXT

• Extending PipelineVertexInputStateCreateInfo:

  • PipelineVertexInputDivisorStateCreateInfoEXT

New Enum Constants

• EXT_VERTEX_ATTRIBUTE_DIVISOR_EXTENSION_NAME

• EXT_VERTEX_ATTRIBUTE_DIVISOR_SPEC_VERSION

• Extending StructureType:

  • STRUCTURE_TYPE_PHYSICAL_DEVICE_VERTEX_ATTRIBUTE_DIVISOR_FEATURES_EXT
  • STRUCTURE_TYPE_PHYSICAL_DEVICE_VERTEX_ATTRIBUTE_DIVISOR_PROPERTIES_EXT
  • STRUCTURE_TYPE_PIPELINE_VERTEX_INPUT_DIVISOR_STATE_CREATE_INFO_EXT

Issues

1) What is the effect of a non-zero value for firstInstance?

RESOLVED: The Vulkan API should follow the OpenGL convention and offset attribute fetching by 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:

    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 divisor and 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.

See Also

PhysicalDeviceVertexAttributeDivisorFeaturesEXT, PhysicalDeviceVertexAttributeDivisorPropertiesEXT, PipelineVertexInputDivisorStateCreateInfoEXT, VertexInputBindingDivisorDescriptionEXT

Document Notes

For more information, see the Vulkan Specification

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