VK_EXT_inline_uniform_block
Other Extension Metadata
Last Modified Date
2018-08-01
IP Status
No known IP claims.
Contributors
- Daniel Rakos, AMD
- Jeff Bolz, NVIDIA
- Slawomir Grajewski, Intel
- Neil Henning, Codeplay
Description
This extension introduces the ability to back uniform blocks directly with descriptor sets by storing inline uniform data within descriptor pool storage. Compared to push constants this new construct allows uniform data to be reused across multiple disjoint sets of drawing or dispatching commands and may enable uniform data to be accessed with fewer indirections compared to uniforms backed by buffer memory.
New Structures
- Extending VkDescriptorPoolCreateInfo:
- Extending VkPhysicalDeviceFeatures2, VkDeviceCreateInfo:
- Extending VkPhysicalDeviceProperties2:
- Extending VkWriteDescriptorSet:
New Enum Constants
VK_EXT_INLINE_UNIFORM_BLOCK_EXTENSION_NAME
VK_EXT_INLINE_UNIFORM_BLOCK_SPEC_VERSION
- Extending VkDescriptorType:
VK_DESCRIPTOR_TYPE_INLINE_UNIFORM_BLOCK_EXT
- Extending VkStructureType:
VK_STRUCTURE_TYPE_DESCRIPTOR_POOL_INLINE_UNIFORM_BLOCK_CREATE_INFO_EXT
VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_INLINE_UNIFORM_BLOCK_FEATURES_EXT
VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_INLINE_UNIFORM_BLOCK_PROPERTIES_EXT
VK_STRUCTURE_TYPE_WRITE_DESCRIPTOR_SET_INLINE_UNIFORM_BLOCK_EXT
Promotion to Vulkan 1.3
Functionality in this extension is included in core Vulkan 1.3, with the EXT suffix omitted. The original type, enum and command names are still available as aliases of the core functionality.
Vulkan 1.3 adds additional functionality
related to this extension in the form of the
maxInlineUniformTotalSize
limit.
Issues
1) Do we need a new storage class for inline uniform blocks vs. uniform blocks?
RESOLVED: No.
The Uniform
storage class is used to allow the same syntax used for
both uniform buffers and inline uniform blocks.
2) Is the descriptor array index and array size expressed in terms of bytes or dwords for inline uniform block descriptors?
RESOLVED: In bytes, but both must be a multiple of 4, similar to how push
constant ranges are specified.
The descriptorCount
of VkDescriptorSetLayoutBinding
thus
provides the total number of bytes a particular binding with an inline
uniform block descriptor type can hold, while the srcArrayElement
,
dstArrayElement
, and descriptorCount
members of
VkWriteDescriptorSet
, VkCopyDescriptorSet
, and
VkDescriptorUpdateTemplateEntry
(where applicable) specify the byte
offset and number of bytes to write/copy to the binding’s backing store.
Additionally, the stride
member of
VkDescriptorUpdateTemplateEntry
is ignored for inline uniform blocks
and a default value of one is used, meaning that the data to update inline
uniform block bindings with must be contiguous in memory.
3) What layout rules apply for uniform blocks corresponding to inline constants?
RESOLVED: They use the same layout rules as uniform buffers.
4) Do we need to add non-uniform indexing features/properties as introduced
by VK_EXT_descriptor_indexing
for inline uniform blocks?
RESOLVED: No, because inline uniform blocks are not allowed to be
arrayed
.
A single binding with an inline uniform block descriptor type corresponds to
a single uniform block instance and the array indices inside that binding
refer to individual offsets within the uniform block (see issue #2).
However, this extension does introduce new features/properties about the
level of support for update-after-bind inline uniform blocks.
5) Is the descriptorBindingVariableDescriptorCount
feature introduced
by VK_EXT_descriptor_indexing
supported for inline uniform blocks?
RESOLVED: Yes, as long as other inline uniform block specific limits are respected.
6) Do the robustness guarantees of robustBufferAccess
apply to inline
uniform block accesses?
RESOLVED: No, similarly to push constants, as they are not backed by buffer memory like uniform buffers.
Version History
- Revision 1, 2018-08-01 (Daniel Rakos)
- Internal revisions