How to use vkCmdSetVertexInputEXT

[TareHimself]

How do I call vkCmdSetVertexInputEXT,
in c++ I can just do
vkCmdSetVertexInputEXT(cmd,...params);
But in c# I cannot find a function to call

[tannergooding]

Extensions and many other APIs are not guaranteed exports and may not even be optimal to call via the export if they exist as one.

Rather, such APIs should be queried via Command Function Pointers instead, as per 46.4 in https://registry.khronos.org/vulkan/specs/1.3-extensions/html/chap46.html#extendingvulkan-extensions

TerraFX.Interop.Vulkan provides several *ManualImports types that contain function pointers to hold the resolved extensions for a given type, such as this one for vkCmdSetVertexInputEXT: https://source.terrafx.dev/#TerraFX.Interop.Vulkan/Vulkan/vulkan/vulkan_core/VkCommandBufferManualImports.cs,2aad28c9e5ec01cf

This helps ensure correctness by only exposing guaranteed exports and pushing developers to correctly enable features and resolve the non-static exports as part of initialization. This can also lead to better overall performance via bypassing the additional checks/queries that might be done for a general entry point that cannot be aware of whether the appropriate setup has taken place and thus must do additional validation or dispatch.

[TareHimself]

Thank you, but could I have an example of how to load and call a function using the c# bindings ?

[tannergooding]

_vkCommandBufferManualImports.vkCmdSetVertexInputEXT = (delegate* unmanaged<VkCommandBuffer, uint, VkVertexInputBindingDescription2EXT*, uint, VkVertexInputAttributeDescription2EXT*, void>)vkGetDeviceProcAddr(vkDevice, (sbyte*)"vkCmdSetVertexInputEXT"u8.GetPointerUnsafe());

That is, you just use vkGetDeviceProcAddr to resolve the method for the specific device as detailed by https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/vkGetDeviceProcAddr.html

This can avoid dispatch overhead and generally be faster than had you resolved it otherwise; noting that vkGetDeviceProcAddr is valid for device or sub-objects created from device such as a VkQueue or VkCommandBuffer.

For other imports, such as those taking a VkInstance you instead want vkGetInstanceProcAddr. This function pointer is also only usable with instance of sub-objects created from instance such as VkPhysicalDevice, VkDevice, VkQueue, or VkCommandBuffer. This means it would also resolve APIs like vkCmdSetVertexInputEXTbut may have overhead as it would need to dispatch to the specific instance for theVkDevice`.