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348990517c
* Bump API patch number and header version number to 29 for this update.
Github Issues:
* Remove redundant constraint on
slink:VkCommandBufferInheritanceInfo::pname:queryFlags (public issue
224).
* Fix typo and remove link in Note in the
<<extended-functionality-instance-extensions-and-devices, Instance
Extensions and Device Extensions>> section (public issue 359).
* Fix erroneous validation statement for the pname:layout member of
slink:VkComputePipelineCreateInfo (public issue 362).
Internal Issues:
* Restore long figure captions using asciidoc sidebar blocks, due to
restrictions of asciidoc syntax (internal issue 101).
* Replace most latexmath equations with comparable markup in straight
asciidoc, which significantly improves time required to fully load and
process the HTML forms of the Specification. There are known minor font
and alignment inconsistencies with MathJax and PDF rendering of
latexmath equations. Please do not file github issues about these. We
are aware of the inconsistencies and will make refinements over time,
while the performance improvements are compelling in at least some major
browsers (internal issue 313).
* Move handcoded validity statements from +vk.xml+ into the Specification
body, easing work in the single-branch model. Specify the distinction
between these explicit statements, and the implicit validity statements
inferred from vk.xml. Validity statements now appear in two blocks for
each command and structure - handcoded "Valid Usage" and the implicit
"Valid Usage (Implicit)" (internal issue 392).
* Add the +returnedonly="false"+ attribute to WSI output structures,
removing incorrectly generated implicit validity statements for
slink:VkDisplayPropertiesKHR, slink:VkDisplayPlanePropertiesKHR,
slink:VkDisplayModePropertiesKHR, slink:VkDisplayPlaneCapabilitiesKHR,
slink:VkSurfaceCapabilitiesKHR, and slink:VkSurfaceFormatKHR structures
(internal issue 486).
* Update slink:VkImageLayout to require the
ename:VK_IMAGE_USAGE_SAMPLED_BIT be set for sampled depth/stencil images
(internal issue 487).
* Use an explicit format specifier string for the date command invocation
in the +Makefile+ instead of the shorthand -R option, which doesn't work
on BSD and MaxOS X date commands (internal issue 500).
Other Issues:
* Use the terms ``allocation scope'' and ``extension scope'' instead of
just ``scope'', and add them to the glossary.
219 lines
8.6 KiB
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219 lines
8.6 KiB
Plaintext
// Copyright (c) 2015-2016 The Khronos Group Inc.
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// Copyright notice at https://www.khronos.org/registry/speccopyright.html
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[[introduction]]
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= Introduction
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This chapter is Informative except for the sections on Terminology and
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Normative References.
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This document, referred to as the ``Vulkan Specification'' or just the
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``Specification'' hereafter, describes the Vulkan graphics system: what it
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is, how it acts, and what is required to implement it.
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We assume that the reader has at least a rudimentary understanding of
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computer graphics.
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This means familiarity with the essentials of computer graphics algorithms
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and terminology as well as with modern GPUs (Graphic Processing Units).
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The canonical version of the Specification is available in the official
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Vulkan Registry, located at URL
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http://www.khronos.org/registry/vulkan/
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[[introduction-whatis]]
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== What is the Vulkan Graphics System?
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Vulkan is an API (Application Programming Interface) for graphics and
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compute hardware.
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The API consists of many commands that allow a programmer to specify shader
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programs, compute kernels, objects, and operations involved in producing
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high-quality graphical images, specifically color images of
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three-dimensional objects.
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[[introduction-programmer]]
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=== The Programmer's View of Vulkan
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To the programmer, Vulkan is a set of commands that allow the specification
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of _shader programs_ or _shaders_, _kernels_, data used by kernels or
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shaders, and state controlling aspects of Vulkan outside of shader
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execution.
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Typically, the data represents geometry in two or three dimensions and
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texture images, while the shaders and kernels control the processing of the
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data, rasterization of the geometry, and the lighting and shading of
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_fragments_ generated by rasterization, resulting in the rendering of
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geometry into the framebuffer.
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A typical Vulkan program begins with platform-specific calls to open a
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window or otherwise prepare a display device onto which the program will
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draw.
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Then, calls are made to open _queues_ to which _command buffers_ are
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submitted.
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The command buffers contain lists of commands which will be executed by the
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underlying hardware.
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The application can: also allocate device memory, associate _resources_ with
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memory and refer to these resources from within command buffers.
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Drawing commands cause application-defined shader programs to be invoked,
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which can: then consume the data in the resources and use them to produce
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graphical images.
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To display the resulting images, further platform-specific commands are made
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to transfer the resulting image to a display device or window.
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[[introduction-implementor]]
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=== The Implementor's View of Vulkan
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To the implementor, Vulkan is a set of commands that allow the construction
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and submission of command buffers to a device.
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Modern devices accelerate virtually all Vulkan operations, storing data and
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framebuffer images in high-speed memory and executing shaders in dedicated
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GPU processing resources.
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The implementor's task is to provide a software library on the host which
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implements the Vulkan API, while mapping the work for each Vulkan command to
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the graphics hardware as appropriate for the capabilities of the device.
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[[introduction-ourview]]
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=== Our View of Vulkan
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We view Vulkan as a pipeline having some programmable stages and some
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state-driven fixed-function stages that are invoked by a set of specific
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drawing operations.
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We expect this model to result in a specification that satisfies the needs
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of both programmers and implementors.
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It does not, however, necessarily provide a model for implementation.
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An implementation must: produce results conforming to those produced by the
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specified methods, but may: carry out particular computations in ways that
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are more efficient than the one specified.
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[[introduction-bugs]]
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== Filing Bug Reports
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Issues with and bug reports on the Vulkan Specification and the API Registry
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can: be filed in the Khronos Vulkan GitHub repository, located at URL
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http://github.com/KhronosGroup/Vulkan-Docs
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Please tag issues with appropriate labels, such as ``Specification'', ``Ref
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Pages'' or ``Registry'', to help us triage and assign them appropriately.
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Unfortunately, GitHub does not currently let users who do not have write
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access to the repository set GitHub labels on issues.
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In the meantime, they can: be added to the title line of the issue set in
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brackets, e.g. ''[Specification]''.
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[[introduction-terminology]]
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== Terminology
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The key words *must*, *required*, *shall* *should*, *recommend*, *may*, and
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*optional* in this document are to be interpreted as described in RFC 2119:
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http://www.ietf.org/rfc/rfc2119.txt
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*must*::
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When used alone, this word, or the term *required*, means that the
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definition is an absolute requirement of the specification.
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When followed by *not* (``must: not'' ), the phrase means that the
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definition is an absolute prohibition of the specification.
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*should*::
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When used alone, this word, or the adjective *recommended*, means that there
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may exist valid reasons in particular circumstances to ignore a particular
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item, but the full implications must be understood and carefully weighed
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before choosing a different course.
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When followed by *not* (``should: not''), the phrase means that there may
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exist valid reasons in particular circumstances when the particular behavior
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is acceptable or even useful, but the full implications should: be
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understood and the case carefully weighed before implementing any behavior
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described with this label.
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*may*::
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This word, or the adjective *optional*, means that an item is truly
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optional.
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One vendor may choose to include the item because a particular marketplace
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requires it or because the vendor feels that it enhances the product while
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another vendor may omit the same item.
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An implementation which does not include a particular option must be
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prepared to interoperate with another implementation which does include the
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option, though perhaps with reduced functionality.
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In the same vein an implementation which does include a particular option
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must be prepared to interoperate with another implementation which does not
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include the option (except, of course, for the feature the option provides).
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The additional terms *can* and *cannot* are to be interpreted as follows:
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*can*::
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This word means that the particular behavior described is a valid choice for
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an application, and is never used to refer to implementation behavior.
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*cannot*::
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This word means that the particular behavior described is not achievable by
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an application.
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For example, an entry point does not exist, or shader code is not capable of
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expressing an operation.
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[NOTE]
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.Note
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==================
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There is an important distinction between *cannot* and *must not*, as used
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in this Specification.
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*Cannot* means something the application literally is unable to express or
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accomplish through the API, while *must not* means something that the
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application is capable of expressing through the API, but that the
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consequences of doing so are undefined and potentially unrecoverable for the
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implementation.
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==================
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ifdef::editing-notes[]
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[NOTE]
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.editing-note
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====
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TODO (Jon) - We might need to augment the RFC 2119 definition of *must not*
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to include some of the previous note, since at present it is defined solely
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in terms of implementation behavior.
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See Gitlab issue #9.
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====
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endif::editing-notes[]
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[[introduction-normative]]
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== Normative References
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Normative references are references to external documents or resources to
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which implementers of Vulkan must: comply.
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[[ieee-754]]
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_IEEE Standard for Floating-Point Arithmetic_, IEEE Std 754-2008,
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http://dx.doi.org/10.1109/IEEESTD.2008.4610935, August, 2008.
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[[data-format]] A.
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Garrard, _Khronos Data Format Specification, version 1.1_,
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https://www.khronos.org/registry/dataformat/specs/1.1/dataformat.1.1.html,
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June, 2016.
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// If the author name is placed on a standalone line, we see the mysterious
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// asciidoc error 'list item index: expected 2 got 10'. Apparently the 'A.'
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// of the previous paragraph and the 'J.' of this one get misinterpreted.
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[[spirv-extended]] J.
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Kessenich, _SPIR-V Extended Instructions for GLSL, Version 1.00_,
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https://www.khronos.org/registry/spir-v/, February 10, 2016.
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[[spirv-spec]] J.
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Kessenich and B.
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Ouriel, _The Khronos SPIR-V Specification, Version 1.00_,
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https://www.khronos.org/registry/spir-v/, February 10, 2016.
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[[vulkan-styleguide]] J.
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Leech and T.
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Hector, _Vulkan Documentation and Extensions: Procedures and Conventions_,
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https://www.khronos.org/registry/vulkan/, July 11, 2016
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[[LoaderAndValidationLayers]]
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_Vulkan Loader Specification and Architecture Overview_,
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https://github.com/KhronosGroup/Vulkan-LoaderAndValidationLayers/blob/master/loader/LoaderAndLayerInterface.md,
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August, 2016.
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