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adadfce8a3
* Update release number to 84.
Public Issues:
* Fix code sample in the `<<VK_EXT_debug_utils>>` extension (public issue
751).
* Fix misleading comment in `vk.xml` for
slink:VkDescriptorBufferInfo::pname:buffer (public pull request 762).
* Fix formatting of deprecation attributes in schema doc (public pull
request 767).
* Change `can` to `may` in the description of
elink:VkSparseImageFormatFlagBits, which are return values from queries
(public pull request 768).
* Prettify generated contact list in extension appendices, adding logos
and a New Issue link (public pull request 770).
* Enable sRGB conversion based on the image view format, not the image
format, in the <<textures-format-conversion, Format Conversion>> section
(public pull request 773).
* Fix typo in equation in the <<primsrast-lines-basic, Basic Line Segment
Rasterization>> section (public pull request 780).
* Fix special characters in GitHub contacts links (public pull request
783).
* Make clean_pdf target remove pdf folder (public pull request 784).
* Fix styleguide bad markup of block continuation (public pull request
792).
Other Issues:
* Allow a zero vertex attribute divisor in the
`<<VK_EXT_vertex_attribute_divisor>>` extension, exposed via the
slink:VkPhysicalDeviceVertexAttributeDivisorFeaturesEXT feature.
* Add missing `structextends="VkDeviceCreateInfo"` to
slink:VkPhysicalDeviceShaderDrawParameterFeatures and
slink:VkPhysicalDeviceBlendOperationAdvancedFeaturesEXT.
New Extensions:
* `VK_KHR_memory_model`
* `VK_EXT_astc_decode_mode`
* `VK_EXT_inline_uniform_block`
114 lines
3.5 KiB
Plaintext
114 lines
3.5 KiB
Plaintext
// Copyright (c) 2018 Khronos Group. This work is licensed under a
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// Creative Commons Attribution 4.0 International License; see
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// http://creativecommons.org/licenses/by/4.0/
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include::meta/VK_EXT_astc_decode_mode.txt[]
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Last Modified Date::
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2018-08-07
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Contributors::
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- Jan-Harald Fredriksen, Arm
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The existing specification requires that low dynamic range (LDR) ASTC
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textures are decompressed to FP16 values per component.
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In many cases, decompressing LDR textures to a lower precision intermediate
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result gives acceptable image quality.
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Source material for LDR textures is typically authored as 8-bit UNORM
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values, so decoding to FP16 values adds little value.
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On the other hand, reducing precision of the decoded result reduces the size
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of the decompressed data, potentially improving texture cache performance
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and saving power.
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The goal of this extension is to enable this efficiency gain on existing
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ASTC texture data.
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This is achieved by giving the application the ability to select the
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intermediate decoding precision.
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Three decoding options are provided:
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* Decode to elink:VK_FORMAT_R16G16B16A16_SFLOAT precision: This is the
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default, and matches the required behavior in the core API.
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* Decode to elink:VK_FORMAT_R8G8B8A8_UNORM precision: This is provided as
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an option in LDR mode.
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* Decode to elink:VK_FORMAT_E5B9G9R9_UFLOAT_PACK32 precision: This is
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provided as an option in both LDR and HDR mode.
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In this mode, negative values cannot be represented and are clamped to
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zero.
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The alpha component is ignored, and the results are as if alpha was 1.0.
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This decode mode is optional and support can be queried via the physical
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device properties.
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=== New Enum Constants
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* Extending elink:VkStructureType:
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** ename:VK_STRUCTURE_TYPE_IMAGE_VIEW_ASTC_DECODE_MODE_EXT
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** ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_ASTC_DECODE_FEATURES_EXT
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=== New Enums
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None.
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=== New Structures
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* slink:VkImageViewASTCDecodeModeEXT
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* slink:VkPhysicalDeviceASTCDecodeFeaturesEXT
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=== New Functions
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None.
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=== Issues
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1) Are implementations allowed to decode at a higher precision than what is
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requested?
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RESOLUTION: No.
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If we allow this, then this extension could be exposed on all
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implementations that support ASTC.
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But developers would have no way of knowing what precision was actually
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used, and thus whether the image quality is sufficient at reduced
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precision.
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2) Should the decode mode be image view state and/or sampler state?
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RESOLUTION: Image view state only.
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Some implementations treat the different decode modes as different
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texture formats.
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=== Example
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Create an image view that decodes to VK_FORMAT_R8G8B8A8_UNORM precision:
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[source,c++]
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----------------------------------------
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VkImageViewASTCDecodeModeEXT decodeMode =
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{
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VK_STRUCTURE_TYPE_IMAGE_VIEW_ASTC_DECODE_MODE_EXT, // sType
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NULL, // pNext
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VK_FORMAT_R8G8B8A8_UNORM // decode mode
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};
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VkImageViewCreateInfo createInfo =
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{
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VK_STRUCTURE_TYPE_IMAGE_VIEW_CREATE_INFO, // sType
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&decodeMode, // pNext
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// flags, image, viewType set to application-desired values
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VK_FORMAT_ASTC_8x8_UNORM_BLOCK, // format
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// components, subresourceRange set to application-desired values
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};
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VkImageView imageView;
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VkResult result = vkCreateImageView(
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device,
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&createInfo,
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NULL,
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&imageView);
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----------------------------------------
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=== Version History
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* Revision 1, 2018-08-07 (Jan-Harald Fredriksen)
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- Initial revision
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