volk is a meta-loader for Vulkan. It allows you to dynamically load entrypoints required to use Vulkan without linking to vulkan-1.dll or statically linking Vulkan loader. Additionally, volk simplifies the use of Vulkan extensions by automatically loading all associated entrypoints. Finally, volk enables loading Vulkan entrypoints directly from the driver which can increase performance by skipping loader dispatch overhead.
volk is written in C89 and supports Windows, Linux, Android and macOS (via MoltenVK).
volk comes with one header and source file; to build it, just add the source file, volk.c, to your build system.
To use volk, you have to include volk.h instead of vulkan/vulkan.h; this is necessary to use function definitions from volk.
If some files in your application include vulkan/vulkan.h and don't include volk.h, this can result in symbol conflicts; consider defining VK_NO_PROTOTYPES when compiling code that uses Vulkan to make sure this doesn't happen.
To initialize volk, call this function first:
VkResult volkInitialize();This will attempt to load Vulkan loader from the system; if this function returns VK_SUCCESS you can proceed to create Vulkan instance.
If this function fails, this means Vulkan loader isn't installed on your system.
After creating the Vulkan instance using Vulkan API, call this function:
void volkLoadInstance(VkInstance instance);This function will load all required Vulkan entrypoints, including all extensions; you can use Vulkan from here on as usual.
If you use volk as described in the previous section, all device-related function calls, such as vkCmdDraw, will go through Vulkan loader dispatch code.
This allows you to transparently support multiple VkDevice objects in the same application, but comes at a price of dispatch overhead which can be as high as 7% depending on the driver and application.
To avoid this, you have one of two options:
- For applications that use just one VkDevice object, load device-related Vulkan entrypoints directly from the driver with this function:
void volkLoadDevice(VkDevice device);- For applications that use multiple VkDevice objects, load device-related Vulkan entrypoints into a table:
void volkLoadDeviceTable(struct VolkDeviceTable* table, VkDevice device);The second option requires you to change the application code to store one VolkDeviceTable per VkDevice and call functions from this table instead.
Device entrypoints are loaded using vkGetDeviceProcAddr; when no layers are present, this commonly results in most function pointers pointing directly at the driver functions, minimizing the call overhead. When layers are loaded, the entrypoints will point at the implementations in the first applicable layer, so this is compatible with any layers including validation layers.
This library is available to anybody free of charge, under the terms of MIT License:
Copyright (c) 2018-2019 Arseny Kapoulkine
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