152 lines
4.7 KiB
Plaintext
152 lines
4.7 KiB
Plaintext
// Copyright (c) 2014-2018 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_KHR_shared_presentable_image.txt[]
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*Last Modified Date*::
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2017-03-20
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*IP Status*::
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No known IP claims.
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*Contributors*::
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- Alon Or-bach, Samsung Electronics
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- Ian Elliott, Google
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- Jesse Hall, Google
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- Pablo Ceballos, Google
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- Chris Forbes, Google
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- Jeff Juliano, NVIDIA
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- James Jones, NVIDIA
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- Daniel Rakos, AMD
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- Tobias Hector, Imagination Technologies
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- Graham Connor, Imagination Technologies
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- Michael Worcester, Imagination Technologies
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- Cass Everitt, Oculus
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- Johannes Van Waveren, Oculus
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This extension extends `<<VK_KHR_swapchain>>` to enable creation of a shared
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presentable image.
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This allows the application to use the image while the presention engine is
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accessing it, in order to reduce the latency between rendering and
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presentation.
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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:VkPresentModeKHR:
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** ename:VK_PRESENT_MODE_SHARED_DEMAND_REFRESH_KHR
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** ename:VK_PRESENT_MODE_SHARED_CONTINUOUS_REFRESH_KHR
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* Extending elink:VkImageLayout:
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** ename:VK_IMAGE_LAYOUT_SHARED_PRESENT_KHR
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* Extending elink:VkStructureType:
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** ename:VK_STRUCTURE_TYPE_SHARED_PRESENT_SURFACE_CAPABILITIES_KHR
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=== New Enums
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None.
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=== New Structures
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* slink:VkSharedPresentSurfaceCapabilitiesKHR
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=== New Functions
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* flink:vkGetSwapchainStatusKHR
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=== Issues
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1) Should we allow a Vulkan WSI swapchain to toggle between normal usage and
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shared presentation usage?
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*RESOLVED*: No.
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WSI swapchains are typically recreated with new properties instead of having
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their properties changed.
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This can also save resources, assuming that fewer images are needed for
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shared presentation, and assuming that most VR applications do not need to
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switch between normal and shared usage.
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2) Should we have a query for determining how the presentation engine
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refresh is triggered?
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*RESOLVED*: Yes.
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This is done via which presentation modes a surface supports.
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3) Should the object representing a shared presentable image be an extension
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of a slink:VkSwapchainKHR or a separate object?
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*RESOLVED*: Extension of a swapchain due to overlap in creation properties
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and to allow common functionality between shared and normal presentable
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images and swapchains.
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4) What should we call the extension and the new structures it creates?
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*RESOLVED*: Shared presentable image / shared present.
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5) Should the pname:minImageCount and pname:presentMode values of the
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slink:VkSwapchainCreateInfoKHR be ignored, or required to be compatible
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values?
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*RESOLVED*: pname:minImageCount must be set to 1, and pname:presentMode
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should be set to either ename:VK_PRESENT_MODE_SHARED_DEMAND_REFRESH_KHR or
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ename:VK_PRESENT_MODE_SHARED_CONTINUOUS_REFRESH_KHR.
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6) What should the layout of the shared presentable image be?
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*RESOLVED*: After acquiring the shared presentable image, the application
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must transition it to the ename:VK_IMAGE_LAYOUT_SHARED_PRESENT_KHR layout
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prior to it being used.
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After this initial transition, any image usage that was requested during
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swapchain creation can: be performed on the image without layout transitions
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being performed.
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7) Do we need a new API for the trigger to refresh new content?
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*RESOLVED*: flink:vkQueuePresentKHR to act as API to trigger a refresh, as
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will allow combination with other compatible extensions to
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flink:vkQueuePresentKHR.
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8) How should an application detect a ename:VK_ERROR_OUT_OF_DATE_KHR error
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on a swapchain using the ename:VK_PRESENT_MODE_SHARED_CONTINUOUS_REFRESH_KHR
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present mode?
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*RESOLVED*: Introduce flink:vkGetSwapchainStatusKHR to allow applications to
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query the status of a swapchain using a shared presentation mode.
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9) What should subsequent calls to flink:vkQueuePresentKHR for
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ename:VK_PRESENT_MODE_SHARED_CONTINUOUS_REFRESH_KHR swapchains be defined to
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do?
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*RESOLVED*: State that implementations may use it as a hint for updated
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content.
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10) Can the ownership of a shared presentable image be transferred to a
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different queue?
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*RESOLVED*: No.
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It is not possible to transfer ownership of a shared presentable image
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obtained from a swapchain created using ename:VK_SHARING_MODE_EXCLUSIVE
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after it has been presented.
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11) How should flink:vkQueueSubmit behave if a command buffer uses an image
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from an ename:VK_ERROR_OUT_OF_DATE_KHR swapchain?
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*RESOLVED*: flink:vkQueueSubmit is expected to return the
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ename:VK_ERROR_DEVICE_LOST error.
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12) Can Vulkan provide any guarantee on the order of rendering, to enable
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beam chasing?
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*RESOLVED*: This could be achieved via use of render passes to ensure strip
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rendering.
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=== Version History
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* Revision 1, 2017-03-20 (Alon Or-bach)
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- Internal revisions
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