xlibswap

CopyrightKhronosGroup2016-Page193SwapchainsUnchained!
(WhatyouneedtoknowaboutVulkanWSI)AlonOr-bach,Chair,VulkanSystemIntegrationSub-Group–May2016@alonorbach(disclaimersapply!
)CopyrightKhronosGroup2016-Page194IntrotoVulkanWindowSystemIntegrationExplicitcontrolforacquisitionandpresentationofimages-DesignedtofittheVulkanAPIandtoday'scompositingwindowsystemsNotallextensionsaresupportedbyeveryplatform-YouMUSTcheckandenabletheextensionsyourapp/engineuses!
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Today'spresentationshouldhelpyougetpresentationworking-Learnhowtopresentthroughaswapchain-OverviewofVulkanobjectsusedbytheWSIextensionsWSIJargonBusterPlatformOurterminologyforanOS/windowsysteme.
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Android,Windows,Wayland,X11viaXCBPresentationEngineTheplatform'scompositorordisplayengineApplicationYourapporgameengineCopyrightKhronosGroup2016-Page195HowmanyWSIextensionsarethereTwocross-platforminstanceextensions-VK_KHR_surface-VK_KHR_displaySix(platform)instanceextensions-VK_KHR_android_surface-VK_KHR_mir_surface-VK_KHR_wayland_surface-VK_KHR_win32_surface-VK_KHR_xcb_surface-VK_KHR_xlib_surfaceTwocross-platformdeviceextensions-VK_KHR_swapchain-VK_KHR_display_swapchainCopyrightKhronosGroup2016-Page196VulkanSurfacesVkSurfaceKHR-Vulkan'swaytoencapsulateanativewindow/surfacePlatform-independentsurfacequeries-Findoutcrucialinformationaboutyoursurface'sproperties-Suchasformat,transform,imageusage-SomeplatformsprovideadditionalqueriesPresentationsupportisperqueuefamily-Animplementationmaysupportmultipleplatformse.
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bothxlibandxcb-OrmaynotsupportpresentationatallPhysicalDeviceAPlatformXQueueFamily2QueueFamily1QueueFamily0PlatformYPhysicalDeviceBQueueFamily1QueueFamily0PhysicalDeviceCQueueFamily1QueueFamily0UnlikeanEGLSurface,creatingaVulkanSurfacedoesn'tmeanyou'vegotyourrendertargetscreated…yetCopyrightKhronosGroup2016-Page197VulkanSwapchains:VK_KHR_swapchainArrayofpresentableimagesassociatedwithasurface-Applicationrequestsaminimumnumberofpresentableimages-Implementationcreatesatleastthatnumber-ImplementationmayhavealimitUpfrontallocationofpresentableimages-Noallocationhitchingatcrucialmoment-Pre-recordfixedcontentcommandbuffersPresentmodedeterminesbehavior-FIFOsupportmandatory-Platformscanoffermailbox,immediate,FIFOrelaxedconstVkSwapchainCreateInfoKHRcreateInfo={VK_STRUCTURE_TYPE_SWAPCHAIN_CREATE_INFO_KHR,//sTypeNULL,//pNext0,//flagsmySurface,//surfacedesiredNumberOfPresentableImages,//minImageCountsurfaceFormat,//imageFormatsurfaceColorSpace,//imageColorSpacemyExtent,//imageExtent1,//imageArrayLayersVK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT,//imageUsageVK_SHARING_MODE_EXCLUSIVE,//imageSharingMode0,//queueFamilyIndexCountNULL,//pQueueFamilyIndicessurfaceProperties.
currentTransform,//preTransformVK_COMPOSITE_ALPHA_INHERIT_BIT_KHR,//compositeAlphaswapchainPresentMode,//presentModeVK_TRUE,//clippedVK_NULL_HANDLE//oldSwapchain};FIFOislikeeglSwapInterval=1Mailbox/ImmediateislikeeglSwapInterval0FIFOrelaxedislikeEXT_swap_control_tearCopyrightKhronosGroup2016-Page198SimilarbutneaterthanhowEGL_KHR_partial_update/EGL_EXT_buffer_ageandpreservedbehaviorachievesthisVulkanSwapchains:They'regood!
Applicationknowswhichimagewithinaswapchainitispresenting-ContentofimagepreservedbetweenpresentsApplicationisresponsibleforexplicitlyrecreatingswapchains-nosurprises-Platforminformsappifcurrentswapchain-Suboptimal:e.
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afterwindowresize,swapchainstillusableforpresentviaimagescaling-SurfaceLost:swapchainnolongerusableforpresent-ApplicationisresponsibletocreateanewswapchainInEGL,theEGLSurfacemayberesizedbytheplatformafteraneglSwapBufferscall.
VulkanrequirestheapplicationtointerveneCopyrightKhronosGroup2016-Page199VulkanSwapchains:They'rejollygood!
Presentingandacquiringareseparateoperations-Noneedtosubmitanewimagetoacquireanotherone,unlesspresentationenginecannotreleaseitApplicationmustonlymodifypresentableimagesithasacquiredPresentationenginemustonlydisplaypresentableimagesthathavebeenpresented!
Stallsinframeloopareverybad!
InEGL,callingeglSwapBuffersbothpresentsthecurrentbackbufferandacquiresanewoneVulkansplitsthisupintoseparateoperationsCopyrightKhronosGroup2016-Page200VK_KHR__surfaceVK_KHR_surfaceVK_KHR_swapchainPlatform-specificAPIsStepstosetupyourpresentableimages1–Createanativewindow/surface2–CreateaVulkansurface3–Queryinformationaboutyoursurface4–CreateaVulkanswapchain5–GetyourpresentableimagesCopyrightKhronosGroup2016-Page201VK_KHR_swapchainVulkanFrameLoop–aseasyas1-2-3!
2–Submitcommandbuffer(s)forthatimage1–Acquirethenextpresentableimage3–Presenttheimage0–CreateyourswapchainLegendSetupSteady-stateResponsetosuboptimal/surface_lostCopyrightKhronosGroup2016-Page202VulkanDisplays:VK_KHR_displayVulkan'swaytodiscoverdisplaydevices(screens,panels)outsideawindowsystem-Reminder:NotsupportedonallplatformsDefinesVkDisplayKHRandVkDisplayModeKHRobjects-RepresentthedisplaydevicesandthemodestheysupportconnectedtoaVkPhysicalDevice-DetermineifadisplaysupportsmultipleplanesthatareblendedtogetherEnablescreationofaVkSurfaceKHRtorepresentadisplayplanePhysicalDeviceSurfaceDisplay0Plane2Plane1Plane0DisplayMode1DisplayMode0Display1DisplayMode1DisplayMode0AVulkandisplayrepresentsanactualdisplay!
(WhereasanEGLDisplayisactuallyjustaconnectiontoadriver–likeaVulkanDevice)CopyrightKhronosGroup2016-Page203VK_KHR_display_swapchainExtendstheinformationprovidedatvkQueuePresentKHR-Whatregiontopresentfromtheswapchainimage-Whatregiontopresenttoonthedisplay-WhetherthedisplayshouldpersisttheimageAddsabilitytocreateasharedswapchain-SwapchainthattakesmultipleVkSwapchainCreateInfoKHRstructs-Allowsmultipledisplaystobepresentedtosimultaneously-Noguaranteethatpresentsareatomic.
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CopyrightKhronosGroup2016-Page204Anyquestionalon.
orbach@samsung.
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