113 lines
3.8 KiB
Plaintext
113 lines
3.8 KiB
Plaintext
include::meta/VK_EXT_inline_uniform_block.txt[]
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*Last Modified Date*::
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2018-08-01
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*IP Status*::
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No known IP claims.
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*Contributors*::
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- Daniel Rakos, AMD
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- Jeff Bolz, NVIDIA
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- Slawomir Grajewski, Intel
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- Neil Henning, Codeplay
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This extension introduces the ability to back uniform blocks directly with
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descriptor sets by storing inline uniform data within descriptor pool
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storage.
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Compared to push constants this new construct allows uniform data to be
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reused across multiple disjoint sets of draw or dispatch commands and may:
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enable uniform data to be accessed with less indirections compared to
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uniforms backed by buffer memory.
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=== New Object Types
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None
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=== New Enum Constants
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* Extending elink:VkStructureType:
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** ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_INLINE_UNIFORM_BLOCK_FEATURES_EXT
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** ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_INLINE_UNIFORM_BLOCK_PROPERTIES_EXT
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** ename:VK_STRUCTURE_TYPE_WRITE_DESCRIPTOR_SET_INLINE_UNIFORM_BLOCK_EXT
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** ename:VK_STRUCTURE_TYPE_DESCRIPTOR_POOL_INLINE_UNIFORM_BLOCK_CREATE_INFO_EXT
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* Extending elink:VkDescriptorType:
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** ename:VK_DESCRIPTOR_TYPE_INLINE_UNIFORM_BLOCK_EXT
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=== New Enums
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None
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=== New Structures
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* slink:VkPhysicalDeviceInlineUniformBlockFeaturesEXT
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* slink:VkPhysicalDeviceInlineUniformBlockPropertiesEXT
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* slink:VkWriteDescriptorSetInlineUniformBlockEXT
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* slink:VkDescriptorPoolInlineUniformBlockCreateInfoEXT
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=== New Functions
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None
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=== New Built-In Variables
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None
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=== Issues
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1) Do we need a new storage class for inline uniform blocks vs uniform
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blocks?
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*RESOLVED*: No.
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The code:Uniform storage class is used to allow the same syntax used for
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both uniform buffers and inline uniform blocks.
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2) Is the descriptor array index and array size expressed in terms of bytes
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or dwords for inline uniform block descriptors?
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*RESOLVED*: In bytes, but both must: be a multiple of 4, similar to how push
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constant ranges are specified.
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The pname:descriptorCount of sname:VkDescriptorSetLayoutBinding thus
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provides the total number of bytes a particular binding with an inline
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uniform block descriptor type can hold, while the pname:srcArrayElement,
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pname:dstArrayElement, and pname:descriptorCount members of
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sname:VkWriteDescriptorSet, sname:VkCopyDescriptorSet, and
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sname:VkDescriptorUpdateTemplateEntry (where applicable) specify the byte
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offset and number of bytes to write/copy to the binding's backing store.
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Additionally, the pname:stride member of
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sname:VkDescriptorUpdateTemplateEntry is ignored for inline uniform blocks
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and a default value of one is used, meaning that the data to update inline
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uniform block bindings with must be contiguous in memory.
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3) What layout rules apply for uniform blocks corresponding to inline
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constants?
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*RESOLVED*: They use the same layout rules as uniform buffers.
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4) Do we need to add non-uniform indexing features/properties as introduced
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by `VK_EXT_descriptor_indexing` for inline uniform blocks?
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*RESOLVED*: No, because inline uniform blocks are not allowed to be
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"arrayed".
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A single binding with an inline uniform block descriptor type corresponds to
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a single uniform block instance and the array indices inside that binding
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refer to individual offsets within the uniform block (see issue #2).
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However, this extension does introduce new features/properties about the
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level of support for update-after-bind inline uniform blocks.
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5) Is the pname:descriptorBindingVariableDescriptorCount feature introduced
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by `VK_EXT_descriptor_indexing` supported for inline uniform blocks?
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*RESOLVED*: Yes, as long as other inline uniform block specific limits are
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respected.
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6) Do the robustness guarantees of pname:robustBufferAccess apply to inline
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uniform block accesses?
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*RESOLVED*: No, similarly to push constants, as they are not backed by
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buffer memory like uniform buffers.
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=== Version History
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* Revision 1, 2018-08-01 (Daniel Rakos)
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- Internal revisions
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