VK_VALVE_mutable_descriptor_type

Other Extension Metadata

Last Modified Date

2020-12-02

IP Status

No known IP claims.

Contributors

Joshua Ashton, Valve
Hans-Kristian Arntzen, Valve

This extension allows applications to reduce descriptor memory footprint by allowing a descriptor to be able to mutate to a given list of descriptor types depending on which descriptor types are written into, or copied into a descriptor set.

The main use case this extension intends to address is descriptor indexing with VK_DESCRIPTOR_BINDING_VARIABLE_DESCRIPTOR_COUNT_BIT where the descriptor types are completely generic, as this means applications can allocate one large descriptor set, rather than having one large descriptor set per descriptor type, which significantly bloats descriptor memory usage and causes performance issues.

This extension also adds a mechanism to declare that a descriptor pool, and therefore the descriptor sets that are allocated from it, reside only in host memory; as such these descriptors can only be updated/copied, but not bound.

These features together allow much more efficient emulation of the raw D3D12 binding model. This extension is primarily intended to be useful for API layering efforts.

New Structures

New Enum Constants

VK_VALVE_MUTABLE_DESCRIPTOR_TYPE_EXTENSION_NAME
VK_VALVE_MUTABLE_DESCRIPTOR_TYPE_SPEC_VERSION
Extending VkDescriptorPoolCreateFlagBits:
- VK_DESCRIPTOR_POOL_CREATE_HOST_ONLY_BIT_VALVE
Extending VkDescriptorSetLayoutCreateFlagBits:
- VK_DESCRIPTOR_SET_LAYOUT_CREATE_HOST_ONLY_POOL_BIT_VALVE
Extending VkDescriptorType:
- VK_DESCRIPTOR_TYPE_MUTABLE_VALVE
Extending VkStructureType:
- VK_STRUCTURE_TYPE_MUTABLE_DESCRIPTOR_TYPE_CREATE_INFO_VALVE
- VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_MUTABLE_DESCRIPTOR_TYPE_FEATURES_VALVE

Version History

Revision 1, 2020-12-01 (Joshua Ashton, Hans-Kristian Arntzen)
- Initial specification, squashed from public draft.