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| <div class="title">Vulkan Memory Allocator </div> </div> |
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| <div class="contents"> |
| <div class="textblock"><p>Version 1.0.1 (2017-07-04)</p> |
| <p>Members grouped: see <a href="modules.html"><b>Modules</b></a>.</p> |
| <p>All members: see <a class="el" href="vk__mem__alloc_8h.html">vk_mem_alloc.h</a>.</p> |
| <h1><a class="anchor" id="problem"></a> |
| Problem Statement</h1> |
| <p>Memory allocation and resource (buffer and image) creation in Vulkan is difficult (comparing to older graphics API-s, like D3D11 or OpenGL) for several reasons:</p> |
| <ul> |
| <li>It requires a lot of boilerplate code, just like everything else in Vulkan, because it is a low-level and high-performance API.</li> |
| <li>There is additional level of indirection: VkDeviceMemory is allocated separately from creating VkBuffer/VkImage and they must be bound together. The binding cannot be changed later - resource must be recreated.</li> |
| <li>Driver must be queried for supported memory heaps and memory types. Different IHV-s provide different types of it.</li> |
| <li>Resources that don't fit in VRAM are not automatically evicted to RAM. Developer must handle out-of-memory errors on his own.</li> |
| <li>It is recommended practice to allocate bigger chunks of memory and assign parts of them to particular resources.</li> |
| </ul> |
| <h1><a class="anchor" id="features"></a> |
| Features</h1> |
| <p>This library is helps game developers to manage memory allocations and resource creation by offering some higher-level functions. Features of the library could be divided into several layers, low level to high level:</p> |
| <ol type="1"> |
| <li>Functions that help to choose correct and optimal memory type based on intended usage of the memory.<ul> |
| <li>Required or preferred traits of the memory are expressed using higher-level description comparing to Vulkan flags.</li> |
| </ul> |
| </li> |
| <li>Functions that allocate memory blocks, reserve and return parts of them (VkDeviceMemory + offset + size) to the user.<ul> |
| <li>Library keeps track of allocated memory blocks, used and unused ranges inside them, finds best matching unused ranges for new allocations, takes all the rules of alignment into consideration.</li> |
| </ul> |
| </li> |
| <li>Functions that can create an image/buffer, allocate memory for it and bind them together - all in one call.</li> |
| </ol> |
| <h1><a class="anchor" id="prequisites"></a> |
| Prequisites</h1> |
| <ul> |
| <li>Self-contained C++ library in single header file. No external dependencies other than standard C and C++ library and of course Vulkan.</li> |
| <li>Public interface in C, in same convention as Vulkan API. Implementation in C++.</li> |
| <li>Interface documented using Doxygen-style comments.</li> |
| <li>Platform-independent, but developed and tested on Windows using Visual Studio.</li> |
| <li>Error handling implemented by returning VkResult error codes - same way as in Vulkan.</li> |
| </ul> |
| <h1><a class="anchor" id="quick_start"></a> |
| Quick Start</h1> |
| <p>In your project code:</p> |
| <ol type="1"> |
| <li>Include "vk_mem_alloc.h" file wherever you want to use the library.</li> |
| <li>In exacly one C++ file define following macro before include to build library implementation.</li> |
| </ol> |
| <pre class="fragment">#define VMA_IMPLEMENTATION |
| #include "vk_mem_alloc.h" |
| </pre><p>At program startup:</p> |
| <ol type="1"> |
| <li>Initialize Vulkan to have VkPhysicalDevice and VkDevice object.</li> |
| <li>Fill <a class="el" href="struct_vma_allocator_create_info.html" title="Description of a Allocator to be created. ">VmaAllocatorCreateInfo</a> structure and create VmaAllocator object by calling <a class="el" href="group__general.html#ga200692051ddb34240248234f5f4c17bb" title="Creates Allocator object. ">vmaCreateAllocator()</a>.</li> |
| </ol> |
| <pre class="fragment">VmaAllocatorCreateInfo allocatorInfo = {}; |
| allocatorInfo.physicalDevice = physicalDevice; |
| allocatorInfo.device = device; |
| |
| VmaAllocator allocator; |
| vmaCreateAllocator(&allocatorInfo, &allocator); |
| </pre><p>When you want to create a buffer or image:</p> |
| <ol type="1"> |
| <li>Fill VkBufferCreateInfo / VkImageCreateInfo structure.</li> |
| <li>Fill <a class="el" href="struct_vma_memory_requirements.html">VmaMemoryRequirements</a> structure.</li> |
| <li>Call <a class="el" href="group__layer3.html#ga6cafa3a644324a1e0c9165494db11648">vmaCreateBuffer()</a> / <a class="el" href="group__layer3.html#ga9646281a3d9abc9f4d0bc5632db117de" title="Function similar to vmaCreateBuffer(). ">vmaCreateImage()</a> to get VkBuffer/VkImage with memory already allocated and bound to it.</li> |
| </ol> |
| <pre class="fragment">VkBufferCreateInfo bufferInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO }; |
| bufferInfo.size = myBufferSize; |
| bufferInfo.usage = VK_BUFFER_USAGE_VERTEX_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT; |
| |
| VmaMemoryRequirements memReq = {}; |
| memReq.usage = VMA_MEMORY_USAGE_GPU_ONLY; |
| |
| VkBuffer buffer; |
| vmaCreateBuffer(allocator, &bufferInfo, &memReq, &buffer, nullptr, nullptr); |
| </pre><p>When no longer needed, destroy your buffer or image using <a class="el" href="group__layer3.html#ga967857c06b8232b2a54936daf36d1535">vmaDestroyBuffer()</a> / <a class="el" href="group__layer3.html#ga9377799736c4a1262b41ee441e5fc877">vmaDestroyImage()</a>. This function would also free memory bound to it.</p> |
| <pre class="fragment">vmaDestroyBuffer(allocator, buffer); |
| </pre><h1><a class="anchor" id="configuration"></a> |
| Configuration</h1> |
| <p>Please check "CONFIGURATION SECTION" in the code to find macros that you can define before each #include of this file or change directly in this file to provide your own implementation of basic facilities like assert, min and max functions, mutex etc. C++ STL is used by default, but changing these allows you to get rid of any STL usage if you want, as many game developers tend to do.</p> |
| <h1><a class="anchor" id="custom_memory_allocator"></a> |
| Custom memory allocator</h1> |
| <p>You can use custom memory allocator by filling optional member <a class="el" href="struct_vma_allocator_create_info.html#a6e409087e3be55400d0e4ccbe43c608d" title="Custom allocation callbacks. ">VmaAllocatorCreateInfo::pAllocationCallbacks</a>. These functions will be passed to Vulkan, as well as used by the library itself to make any CPU-side allocations.</p> |
| <h1><a class="anchor" id="thread_safety"></a> |
| Thread safety</h1> |
| <p>All calls to functions that take VmaAllocator as first parameter are safe to call from multiple threads simultaneously, synchronized internally when needed. </p> |
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