Quick start

Project setup

Vulkan Memory Allocator comes in form of a "stb-style" single header file. You don't need to build it as a separate library project. You can add this file directly to your project and submit it to code repository next to your other source files.

"Single header" doesn't mean that everything is contained in C/C++ declarations, like it tends to be in case of inline functions or C++ templates. It means that implementation is bundled with interface in a single file and needs to be extracted using preprocessor macro. If you don't do it properly, you will get linker errors.

To do it properly:

1. Include "vk_mem_alloc.h" file in each CPP file where you want to use the library. This includes declarations of all members of the library.
2. In exactly one CPP file define following macro before this include. It enables also internal definitions.

#define VMA_IMPLEMENTATION
#include "vk_mem_alloc.h"

It may be a good idea to create dedicated CPP file just for this purpose.

This library includes header <vulkan/vulkan.h>, which in turn includes <windows.h> on Windows. If you need some specific macros defined before including these headers (like WIN32_LEAN_AND_MEAN or WINVER for Windows, VK_USE_PLATFORM_WIN32_KHR for Vulkan), you must define them before every #include of this library.

This library is written in C++, but has C-compatible interface. Thus you can include and use vk_mem_alloc.h in C or C++ code, but full implementation with VMA_IMPLEMENTATION macro must be compiled as C++, NOT as C. Some features of C++14 used. STL containers, RTTI, or C++ exceptions are not used.

Initialization

At program startup:

1. Initialize Vulkan to have VkPhysicalDevice, VkDevice and VkInstance object.
2. Fill VmaAllocatorCreateInfo structure and create VmaAllocator object by calling vmaCreateAllocator().

Only members physicalDevice, device, instance are required. However, you should inform the library which Vulkan version do you use by setting VmaAllocatorCreateInfo::vulkanApiVersion and which extensions did you enable by setting VmaAllocatorCreateInfo::flags (like VMA_ALLOCATOR_CREATE_BUFFER_DEVICE_ADDRESS_BIT for VK_KHR_buffer_device_address). Otherwise, VMA would use only features of Vulkan 1.0 core with no extensions.

You may need to configure importing Vulkan functions. There are 3 ways to do this:

1. If you link with Vulkan static library (e.g. "vulkan-1.lib" on Windows):
   • You don't need to do anything.
   • VMA will use these, as macro VMA_STATIC_VULKAN_FUNCTIONS is defined to 1 by default.
2. If you want VMA to fetch pointers to Vulkan functions dynamically using vkGetInstanceProcAddr, vkGetDeviceProcAddr (this is the option presented in the example below):
   • Define VMA_STATIC_VULKAN_FUNCTIONS to 0, VMA_DYNAMIC_VULKAN_FUNCTIONS to 1.
   • Provide pointers to these two functions via VmaVulkanFunctions::vkGetInstanceProcAddr, VmaVulkanFunctions::vkGetDeviceProcAddr.
   • The library will fetch pointers to all other functions it needs internally.
3. If you fetch pointers to all Vulkan functions in a custom way, e.g. using some loader like Volk:
   • Define VMA_STATIC_VULKAN_FUNCTIONS and VMA_DYNAMIC_VULKAN_FUNCTIONS to 0.
   • Pass these pointers via structure VmaVulkanFunctions.

VmaVulkanFunctions vulkanFunctions = {};
vulkanFunctions.vkGetInstanceProcAddr = &vkGetInstanceProcAddr;
vulkanFunctions.vkGetDeviceProcAddr = &vkGetDeviceProcAddr;

VmaAllocatorCreateInfo allocatorCreateInfo = {};
allocatorCreateInfo.vulkanApiVersion = VK_API_VERSION_1_2;
allocatorCreateInfo.physicalDevice = physicalDevice;
allocatorCreateInfo.device = device;
allocatorCreateInfo.instance = instance;
allocatorCreateInfo.pVulkanFunctions = &vulkanFunctions;

VmaAllocator allocator;
vmaCreateAllocator(&allocatorCreateInfo, &allocator);

Resource allocation

When you want to create a buffer or image:

1. Fill VkBufferCreateInfo / VkImageCreateInfo structure.
2. Fill VmaAllocationCreateInfo structure.
3. Call vmaCreateBuffer() / vmaCreateImage() to get VkBuffer/VkImage with memory already allocated and bound to it, plus VmaAllocation objects that represents its underlying memory.

VkBufferCreateInfo bufferInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO };
bufferInfo.size = 65536;
bufferInfo.usage = VK_BUFFER_USAGE_VERTEX_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT;

VmaAllocationCreateInfo allocInfo = {};
allocInfo.usage = VMA_MEMORY_USAGE_AUTO;

VkBuffer buffer;
VmaAllocation allocation;
vmaCreateBuffer(allocator, &bufferInfo, &allocInfo, &buffer, &allocation, nullptr);

Don't forget to destroy your objects when no longer needed:

vmaDestroyBuffer(allocator, buffer, allocation);
vmaDestroyAllocator(allocator);