GDC : Mar16.pdf
Jan 02, 2017
Copyright Khronos Group 2016 - Page 142
Swapchains Unchained!(What you need to know about Vulkan WSI)
Alon Or-bach, Chair, Vulkan Window System Integration Sub-Group March 2016
Copyright Khronos Group 2016 - Page 143
Intro to Vulkan Window System Integration Explicit control for acquisition and
presentation of images - Designed to fit the Vulkan API and todays
compositing window systems
Not all extensions are supported by every platform- You MUST check and enable the extensions
your app/engine uses!!!
Todays presentation should help you get presentation working- Learn how to present through a swapchain- Overview of Vulkan objects used by the WSI
extensions
WSI Jargon Buster Platform
Our terminology for an OS
/ window system e.g.
Android, Windows,
Wayland, X11 via XCB
Presentation EngineThe platforms compositor or display engine
ApplicationYour app or game engine
Copyright Khronos Group 2016 - Page 144
How many WSI extensions are there? Two cross-platform instance extensions- VK_KHR_surface- VK_KHR_display
Six (platform) instance extensions- VK_KHR_android_surface- VK_KHR_mir_surface- VK_KHR_wayland_surface- VK_KHR_win32_surface- VK_KHR_xcb_surface- VK_KHR_xlib_surface
Two cross-platform device extensions- VK_KHR_swapchain- VK_KHR_display_swapchain
Copyright Khronos Group 2016 - Page 145
Vulkan Surfaces VkSurfaceKHR- Vulkans way to encapsulate a native
window / surface
Platform-independent surface queries- Find out crucial information about your
surfaces properties- e.g., if presentation is supported by a
particular queue on a particular device
- Some platforms provide additional queries An implementation may support multiple
platforms- e.g., both xlib and xcb
Physical Device A
Platform X
Queue Family 2
Queue Family 1 Queue
Family 0
Platform Y
Physical Device B
Queue Family 1Queue
Family 0
Surface from
Platform X
Physical Device C
Queue Family 1Queue
Family 0
Copyright Khronos Group 2016 - Page 146
Vulkan Swapchains: VK_KHR_swapchain Array of presentable images associated with
a surface- Application requests a minimum number
of presentable images
- Implementation creates at least that number
- Implementation may have a limit Upfront allocation of presentable images- No allocation hitching at crucial moment- Pre-record fixed content command buffers
Present mode determines behavior- FIFO support mandatory- Platforms can offer mailbox,
immediate, FIFO relaxed
const VkSwapchainCreateInfoKHR createInfo ={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};
Copyright Khronos Group 2016 - Page 147
Vulkan Swapchains: Theyre good! Application knows which image within a
swapchain it is presenting- Content of image preserved between
presents
Application is responsible for explicitly recreating swapchains - no surprises- Platform informs app if current swapchain- Suboptimal: e.g. after window resize,
swapchain still usable for present via image
scaling
- Surface Lost: swapchain no longer usable for present
- Application is responsible to create a new swapchain
Copyright Khronos Group 2016 - Page 148
Vulkan Swapchains: Theyre jolly good! Presenting and acquiring are separate
operations- No need to submit a new image to acquire
another one, unless presentation engine
cannot release it
Application must only modify presentable images it has acquired
Presentation engine must only display presentable images that have been presented!
Stalls in frame loop are very bad!
Copyright Khronos Group 2016 - Page 149
VK_KHR__surface
VK_KHR_surface
VK_KHR_swapchain
Platform-specific APIs
Steps to setup your presentable images1 Create a native window/surface
2 Create a Vulkan surface
3 Query information about your surface
4 Create a Vulkan swapchain
5 Get your presentable images
Copyright Khronos Group 2016 - Page 150
VK_KHR_swapchain
Vulkan Frame Loop as easy as 1-2-3!
2 Submit command buffer(s) for that image
1 Acquire the next presentable image 3 Present the image
0 Create your swapchain
LegendSetup
Steady-state
Response to suboptimal
/ surface_lost
Copyright Khronos Group 2016 - Page 151
Vulkan Displays: VK_KHR_display Vulkans way to discover display devices
(screens, panels) outside a window system- Reminder: Not supported on all platforms
Defines VkDisplayKHR and VkDisplayModeKHR objects- Represent the display devices and the
modes they support connected to a
VkPhysicalDevice
- Determine if a display supports multiple planes that are blended together
Enables creation of a VkSurfaceKHR to represent a display plane
Physical Device
Surface
Display 0
Plane 2Plane 1
Plane 0
Display Mode 1Display
Mode 0
Display 1
Display Mode 1Display
Mode 0
Copyright Khronos Group 2016 - Page 152
VK_KHR_display_swapchain Extends the information provided at vkQueuePresentKHR- What region to present from the swapchain image- What region to present to on the display- Whether the display should persist the image
Adds ability to create a shared swapchain- Swapchain that takes multiple VkSwapchainCreateInfoKHR structs- Allows multiple displays to be presented to simultaneously- No guarantee that presents are atomic ...presently!
Copyright Khronos Group 2016 - Page 153
Any question?
[email protected]@alonorbach (disclaimers apply!)
Copyright Khronos Group 2016 - Page 1
LunarG SDK for VulkanKaren Ghavam, CEO
Karl Schultz, Principal EngineerJon Ashburn, Principal Engineer
Copyright Khronos Group 2016 - Page 2
Enter the Raffle for your prize!Congratulations!
You are the recipient of the Vulkan Programming Guide, courtesy of LunarG!
Is your OpenGL Programming Guide getting lonely? Well, it will soon have a companion. In August 2016, when the Vulkan Programming Guide becomes available, LunarG will ship it directly to you!
In the meantime, visit LunarXchange (Vulkan.lunarg.com) for the LunarG SDK for Vulkan, and accept this book bag, anxiously awaiting its Vulkan Programming Guide.
Copyright Khronos Group 2016 - Page 3
LunarG SDK Loader Binary Validation Layer Libraries Vulkan trace and replay tools- vktrace- vkreplay
SPIR-V Tools- GLSL Validator - SPIR-V Disassembler and Assembler - SPIR-V Remapper
RenderDoc* Sample Programs
*For a detailed demonstration of RenderDoc dont miss:Practical Development for Vulkan (presented by Valve Software). Thursday. 12:45 1:45. Room 3009, West Hall
Copyright Khronos Group 2016 - Page 4
Download the LunarG SDK for Vulkan at LunarXchange: vulkan.lunarg.com
Version 1.0.5.0 now available!
Copyright Khronos Group 2016 - Page 5
The Power of a Layered Ecosystem
Development pathValidation
layer
Debug layer
Other layers
Production path
Vulkan application
Installable Client Driver
Vulkan application
Installable Client Driver
Loader
Loader
Copyright Khronos Group 2016 - Page 6
Layers: Fully IntegratedProgrammatic Approach
Vulkan application
Debug Report
Callback
Installable Client Driver
Layer
Application supplies list
of layers
Application handles messages in
callback
Layers report results as
messages
Loader
Copyright Khronos Group 2016 - Page 7
Layers: Externally ActivatedAd-hoc Approach
Vulkan application
Debug Report
Callback
Installable Client Driver
Layer
User sets environment variables:
VK_INSTANCE_LAYER=layer name
Default Debug Report writes to output stream
Layers report results as
messages
Loader
Layer Settings File
Copyright Khronos Group 2016 - Page 8
Demo Well Be Using
HologramBy
Chia-I Wu (olv)
Well-written Vulkan demo Simulation of 5000 moving objects Demonstrates multi-threaded command
buffer recording Can be found in: https://github.com/LunarG/VulkanSamples
Copyright Khronos Group 2016 - Page 9
Demo!
Watch the demo for a minute or so
Copyright Khronos Group 2016 - Page 10
A Few Hologram Internals Object Data
5000 ShaderParamBlocks
struct ShaderParamBlock {float light_pos[4];float light_color[4];float model[4 * 4];float view_projection[4 * 4];
};
One ShaderParamBlock per Object
For Each Frame and For Each Object: Modify ShaderParamBlock BindDescriptorSet
Two Frames of Object Data
Copyright Khronos Group 2016 - Page 11
Modify DemoLets add code to modulate the transparency
