162

2

## Extension and Version Dependencies

• Requires Vulkan 1.0

• Requires VK_KHR_get_physical_device_properties2

• Requires VK_KHR_maintenance3

## Contact

2017-10-02

Interactions and External Dependencies
• Promoted to Vulkan 1.2 Core

Contributors
• Jeff Bolz, NVIDIA

• Daniel Rakos, AMD

• Slawomir Grajewski, Intel

• Tobias Hector, Imagination Technologies

### Description

This extension adds several small features which together enable applications to create large descriptor sets containing substantially all of their resources, and selecting amongst those resources with dynamic (non-uniform) indexes in the shader. There are feature enables and SPIR-V capabilities for non-uniform descriptor indexing in the shader, and non-uniform indexing in the shader requires use of a new NonUniformEXT decoration defined in the SPV_EXT_descriptor_indexing SPIR-V extension. There are descriptor set layout binding creation flags enabling several features:

• Descriptors can be updated after they are bound to a command buffer, such that the execution of the command buffer reflects the most recent update to the descriptors.

• Descriptors that are not used by any pending command buffers can be updated, which enables writing new descriptors for frame N+1 while frame N is executing.

• Relax the requirement that all descriptors in a binding that is “statically used” must be valid, such that descriptors that are not accessed by a submission need not be valid and can be updated while that submission is executing.

• The final binding in a descriptor set layout can have a variable size (and unsized arrays of resources are allowed in the GL_EXT_nonuniform_qualifier and SPV_EXT_descriptor_indexing extensions).

Note that it is valid for multiple descriptor arrays in a shader to use the same set and binding number, as long as they are all compatible with the descriptor type in the pipeline layout. This means a single array binding in the descriptor set can serve multiple texture dimensionalities, or an array of buffer descriptors can be used with multiple different block layouts.

There are new descriptor set layout and descriptor pool creation flags that are required to opt in to the update-after-bind functionality, and there are separate maxPerStage* and maxDescriptorSet* limits that apply to these descriptor set layouts which may be much higher than the pre-existing limits. The old limits only count descriptors in non-updateAfterBind descriptor set layouts, and the new limits count descriptors in all descriptor set layouts in the pipeline layout.

### New Enum Constants

• VK_EXT_DESCRIPTOR_INDEXING_EXTENSION_NAME

• VK_EXT_DESCRIPTOR_INDEXING_SPEC_VERSION

• Extending VkDescriptorBindingFlagBits:

• VK_DESCRIPTOR_BINDING_PARTIALLY_BOUND_BIT_EXT

• VK_DESCRIPTOR_BINDING_UPDATE_AFTER_BIND_BIT_EXT

• VK_DESCRIPTOR_BINDING_UPDATE_UNUSED_WHILE_PENDING_BIT_EXT

• VK_DESCRIPTOR_BINDING_VARIABLE_DESCRIPTOR_COUNT_BIT_EXT

• Extending VkDescriptorPoolCreateFlagBits:

• VK_DESCRIPTOR_POOL_CREATE_UPDATE_AFTER_BIND_BIT_EXT

• Extending VkDescriptorSetLayoutCreateFlagBits:

• VK_DESCRIPTOR_SET_LAYOUT_CREATE_UPDATE_AFTER_BIND_POOL_BIT_EXT

• Extending VkResult:

• VK_ERROR_FRAGMENTATION_EXT

• Extending VkStructureType:

• VK_STRUCTURE_TYPE_DESCRIPTOR_SET_LAYOUT_BINDING_FLAGS_CREATE_INFO_EXT

• VK_STRUCTURE_TYPE_DESCRIPTOR_SET_VARIABLE_DESCRIPTOR_COUNT_ALLOCATE_INFO_EXT

• VK_STRUCTURE_TYPE_DESCRIPTOR_SET_VARIABLE_DESCRIPTOR_COUNT_LAYOUT_SUPPORT_EXT

• VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_DESCRIPTOR_INDEXING_FEATURES_EXT

• VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_DESCRIPTOR_INDEXING_PROPERTIES_EXT

### Promotion to Vulkan 1.2

Functionality in this extension is included in core Vulkan 1.2, with the EXT suffix omitted. However, if Vulkan 1.2 is supported and this extension is not, the descriptorIndexing capability is optional. The original type, enum and command names are still available as aliases of the core functionality.

### Version History

• Revision 1, 2017-07-26 (Jeff Bolz)

• Internal revisions

• Revision 2, 2017-10-02 (Jeff Bolz)

• ???