代写代考 COMP5822M – High Perf. Graphics

Lecture 2: Vulkan, Part 1
COMP5822M – High Perf. Graphics

– Practicalstuff – WhyVulkan? – VulkanBasics

COMP5822M – High Perf. Graphics

Practical, I
– Labsupportsessions,suggestion
– Tuesday afternoon, online, 15.00 to <=17.00 - Friday afternoon, in pers., 14:00 to <=16.00 - (Overlap with other lab. Right now difficult to make it earlier. Might be able to adjust later.) - WillpostonTeams,candiscussfurther there. COMP5822M – High Perf. Graphics Practical, II - Vulkan 1.3 released with perfect timing - Will mention a few new features it brings - Was considering doing that anyway 😉 COMP5822M – High Perf. Graphics Practical, III - Exercises:Vulkan1.1+extensionsfornow? - Less problematic for Apple-y devices - One of the reasons for 1.2 was made obsolete by 1.3 anway... COMP5822M – High Perf. Graphics Practical, IV - Quickcheck–C++knowledge. COMP5822M – High Perf. Graphics Practical, IV - Quickcheck–C++knowledge. - Constructors & Destructors? - Exceptions? - Move semantics / move-only objects? - Templates? COMP5822M – High Perf. Graphics Why Vulkan? COMP5822M – High Perf. Graphics Why Vulkan? - Twoquestions,actually - Why would you (as a programmer) pick - Why did we pick Vulkan for COMP5822? COMP5822M – High Perf. Graphics Why Vulkan? - Twoquestions,actually - Why would you (as a programmer) pick - Why did we pick Vulkan for COMP5822? - Give you some insight into why Vulkan does things a certain way. COMP5822M – High Perf. Graphics A Modern System COMP5822M – High Perf. Graphics - GPU is a separate device/chip - Runs asynchronously with everything else - Has a lot of internal parallelism - Different GPUs with different tech/features - Multiple GPUs - Which can display stuff on the screen? COMP5822M – High Perf. Graphics Issues, II - Different types of memory - System RAM and VRAM - Not all GPUs have VRAM - Not all system RAM is equal (special regions) - Not all VRAM is equal (special regions) COMP5822M – High Perf. Graphics Issues, III - Minimize unnecessary processing - Need to “drive” the GPU from CPU - But CPU has other tasks too - “Draw calls” COMP5822M – High Perf. Graphics Vulkan Principles - Designprinciples - Multi-thread, multi-device - Low overhead - Explicit control - Repeatable & predictable - Other modern APIs similar - E.g.,DirectXorMetal COMP5822M – High Perf. Graphics Contrast: OpenGL? - Not multi-device - Badatmulti-threading - Pain to program - Global State - Difficult to write independent code - (Global State has been reduced lately) COMP5822M – High Perf. Graphics Contrast: OpenGL? - Behindthescenes“magic” - E.g., shadow buffers, shader recompiles, ... - Expensivealways-onvalidation - Required to report errors in some cases - Thatsaid... - Modern OpenGL is pretty nice - Still, lots of difficult-to-diagnose COMP5822M – High Perf. Graphics Vulkan vs OpenGL - Less “magic” - More explicit & verbose - Less “magic” - More explicit & verbose COMP5822M – High Perf. Graphics Vulkan vs OpenGL - No global state, little implicit state - Not actively hostile to multi-threading - Consistentstyleandconcepts - Validation on demand - Validation is standardized (and quite good) - More expensive than OpenGL, but that’s OK - Only enable it for development/debugging COMP5822M – High Perf. Graphics Other reasons - Crossplatform - Desktop: Windows, Linux, ~MacOS (MoltenVK) - Mobile: Android, ~iOS (MoltenVK) - Others? (Google Stadia?) - Needs to deal with different archs - Traditional (sort-last) vs Tiled (~sort-middle) - Extra complexity. COMP5822M – High Perf. Graphics Additional facts - Extensions (similar to OpenGL) - Fast support for new features. - Layersystem - E.g. used for validation - Can write your own - Many existing ones are open source COMP5822M – High Perf. Graphics COMP5822M – High Perf. Graphics - At the core, Vulkan is an API specification that conformant hardware implementations follow. (https://github.com/KhronosGroup/Vulkan- Guide/blob/master/chapters/what_is_vulkan.md) - Note: software implementations do exist. COMP5822M – High Perf. Graphics - Vulkan specification defines an interface - We use it to talk to the GPU / implementation - Interface defines functions relating to - Graphics - Ray tracing (extension) - Video encoding/decoding (extension) -... - (Resource management) COMP5822M – High Perf. Graphics - Specificationdefineswhatthe implementation should do - You can read it online - XML file (vk.xml) with definitions/names - “Cinterface” COMP5822M – High Perf. Graphics The C Interface - DefaultAPIforVulkan - “Lowest level” - We’ll use it in COMP5822 - Common elsewhere (vulkan-tutorial, ...) - Easiest to find via Google et al. - Distinct naming scheme COMP5822M – High Perf. Graphics Side note: other options - C++:vulkan.hpp(plusothers?) - Otherlanguagebindings(Rust,...) - Typically generated from the same XML - Rollyourown? - Parse the XML, output desired API/wrappers - LoadLibrary() / dlopen() etc COMP5822M – High Perf. Graphics Vulkan Stack Application COMP5822M – High Perf. Graphics Vulkan Stack vkFoo( deviceA, ... ) Application COMP5822M – High Perf. Graphics Vulkan Stack vkFoo( deviceA, ... ) Application vkFoo( deviceA, ... ) COMP5822M – High Perf. Graphics Vulkan Stack vkFoo( deviceA, ... ) Application vkBar( deviceB, ... ) vkFoo( deviceA, ... ) COMP5822M – High Perf. Graphics vkBar( deviceB, ... ) Vulkan Stack Application vkFoo( deviceA, ... ) vkBar( deviceB, ... ) vkFoo( deviceA, ... ) COMP5822M – High Perf. Graphics vkBar( deviceB, ... ) vkBar( deviceB, ... ) Vulkan Stack Application COMP5822M – High Perf. Graphics - Vulkan allows us to load layers - LayerscaninterceptVulkanAPIcalls COMP5822M – High Perf. Graphics Vulkan Stack vkFoo( deviceA, ... ) Application vkFoo( deviceA, ... ) Layer A Device A vkFoo( deviceA, ... ) COMP5822M – High Perf. Graphics See: https://renderdoc.org/vulkan-layer-guide.html - Example:VK_KHRONOS_validation - Checks for various errors. - Whylayersforthis? - Validation is expensive - Load only during development - Skip during “normal” deployment COMP5822M – High Perf. Graphics Vulkan Stack vkFoo( deviceA, ... ) Application Loader Layer A vkFoo( deviceA, ... ) vkFoo( deviceA, ... ) COMP5822M – High Perf. Graphics See: https://renderdoc.org/vulkan-layer-guide.html vkBar( deviceB, ... ) Vulkan Stack Application COMP5822M – High Perf. Graphics Vulkan Stack Application Volk Vulkan Device A Loader “Meta-loader for Vulkan” https://github.com/zeux/volk COMP5822M – High Perf. Graphics - Meta-loader, 3rd party - LoadstheVulkanLoaderatruntime - LoadLibrary() / dlopen() - Simplifies my life. 🙂 - I can give you Volk (2 sources) - Don’t need to figure out how to link etc. on your system. COMP5822M – High Perf. Graphics - Volk’s API looks just like the standard API. - However: #include instead of
#include
– Calls to volkInitialize(), volkLoadInstance() andoptionally
volkLoadDevice()
COMP5822M – High Perf. Graphics

volkLoadDevice()
volkLoadDevice( deviceB )
Application Volk Vulkan Device A Loader
If you need to work with multiple devices, read Volk’s documentation.
COMP5822M – High Perf. Graphics

volkLoadDevice()
volkLoadDevice( deviceB )
Application Volk

COMP5822M – High Perf. Graphics
Works with layers, just no/less benefit.

– Note: loading device functions is only really useful if you’re bound by CPU performance
– Even then, the gains are likely to be quite small.
COMP5822M – High Perf. Graphics

Vulkan C API
COMP5822M – High Perf. Graphics

Vulkan C API
– Objectoriented.
COMP5822M – High Perf. Graphics

Vulkan C API
– Objectoriented.
– Handles = references to objects
– vkCreateFoo() … vkDestroyFoo()
– vkDoThing( fooHandle, … )
COMP5822M – High Perf. Graphics

Vulkan C API
– We are required to clean up after ourselves.
– I.e., call vkDestroyFoo()
– Cannot do that while object is in use
– Either on GPU or on CPU
– No internal reference counting or similar
COMP5822M – High Perf. Graphics

Vulkan C API – Conventions
– Constants:VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO – Types:VkResult, VkInstance, VkInstanceCreateInfo – Functions:vkCreateInstance()
COMP5822M – High Perf. Graphics

Vulkan C API – Conventions
– Constants:VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO – Types:VkResult, VkInstance, VkInstanceCreateInfo – Functions:vkCreateInstance()
Enumeration
COMP5822M – High Perf. Graphics

Vulkan C API – General Style
VkResult vkCreateImage(
VkDevice device, // object handle VkImageCreateInfo const* pInfo, // parameters VkAllocationCallbacks const* pCallbacks, // nullptr (ignored for now) VkImage* pImage // “output”
COMP5822M – High Perf. Graphics

Vulkan C API – General Style
– Returnvalue:VkResult – VK_SUCCESS
– error codes
– “conditional” success conditions
– Typicalreturnvalue
– Thoughsomefunctionsarevoid
– E.g. vkDestroyImage()
COMP5822M – High Perf. Graphics

Vulkan C API – General Style
– VkDevice: handle to device
– Image is created for/on this device
COMP5822M – High Perf. Graphics

Vulkan C API – General Style
– VkImageCreateInfo
– Parameters to image creation
COMP5822M – High Perf. Graphics

Vulkan C API – General Style
COMP5822M – High Perf. Graphics

Vulkan C API – General Style
– VkAllocationCallbacks
– Enables control over internal memory allocations
– System member
– We ignore this mostly (=set to nullptr)
– System memory allocator is good enough – Difficult to beat in the general case anyway
COMP5822M – High Perf. Graphics

Vulkan C API – General Style
– VkImage: out pointer
– Handle to newly created image is placed here
COMP5822M – High Perf. Graphics

Vulkan C API – Code Example
VkDevice device = …;
VkImageCreateInfo imageInfo{}; // “value initialize”, i.e. zero out struct imageInfo.sType = VK_STRUCTURE_TYPE_IMAGE_CREATE_INFO;
//imageInfo.pNext = nullptr; // already nullptr due to init with {}
imageInfo.format = VK_FORMAT_R8G8B8A8_SRGB; …
VkImage image = VK_NULL_HANDLE;
auto const res = vkCreateImage( device, &imageInfo, nullptr, &image );
if( VK_SUCCESS != res ) error( … );
COMP5822M – High Perf. Graphics

Vulkan C API – Code Example
VkDevice device = …;
VkImageCreateInfo imageInfo{}; // “value initialize”, i.e. zero out struct imageInfo.sType = VK_STRUCTURE_TYPE_IMAGE_CREATE_INFO;
//imageInfo.pNext = nullptr; // already nullptr due to init with {}
imageInfo.format = VK_FORMAT_R8G8B8A8_SRGB; …
VkImage image = VK_NULL_HANDLE;
if( auto const res = vkCreateImage( … ); VK_SUCCESS != res ) // C++17 if()
error( … );
COMP5822M – High Perf. Graphics

– Typicallypackparametersintostructs
– Manystructshave.sType and.pNext
– sType needs to be set correctly
– pNext mostly left at nullptr
– Used for extensions (pNext points at additional
structs with more parameters)
– Someexceptions(VkExtent2D,…)
– Although some have been updated to have
them after all.
COMP5822M – High Perf. Graphics

Thanks for your attention.
COMP5822M – High Perf. Graphics

Bonus Slide – Extensions / sType, .pNext
VkPhysicalDeviceVulkan12Features featsV12{};
featsV12.sType = VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_VULKAN12_FEATURES; …
VkPhysicalDeviceFeatures2 feats{};
feats.sType = VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_FEATURES_2; feats.pNext = &featsV12;
vkGetPhysicalDeviceFeatures2( physicalDevice, &feats );
COMP5822M – High Perf. Graphics

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