---
id: vk
title: Vk
order: 61
---

Vulkan for Ludic. <code>Vk.*</code> binds <strong>Vulkan 1.0–1.4</strong> and the extensions a modern renderer is built around — swapchain and HDR colour spaces, ray query and acceleration structures, opacity micromaps, mesh shaders, variable rate shading, memory budget, pipeline libraries, NVIDIA low latency, and portability enumeration for MoltenVK. Every command is a method named by its snake case (<code>vkCreateInstance</code> → <code>Vk.create_instance</code>, <code>vkCmdDrawIndexedIndirectCount</code> → <code>Vk.cmd_draw_indexed_indirect_count</code>), every <code>VK_*</code> constant is available as written, and every struct has its size and field offsets as constants: <code>VkDeviceCreateInfo_sizeof</code>, <code>VkDeviceCreateInfo_queueCreateInfoCount</code>. The binding is generated by <code>ludic-dev vkgen</code> from the Vulkan registry (<code>vk.xml</code>), and every size and offset is checked against the SDK's C headers.

A struct is plain memory filled by field name: <code>bytes(Vk…_sizeof)</code>, <code>Vk.zero(p, n)</code>, then <code>Vk.put_i32</code> / <code>Vk.put_i64</code> / <code>Vk.put_ptr(p, offset, value)</code>, read back with <code>Vk.get_i32</code> / <code>get_i64</code> / <code>get_ptr</code>, and <code>Vk.at(p, offset)</code> for a nested struct or an inline array. Numbers follow the C types: a <code>float</code> is its IEEE bit pattern in an <code>int</code>, and <code>uint64_t</code>, <code>VkDeviceSize</code> and non-dispatchable handles are <code>long</code>. A negative <code>long</code> has to come from a <code>long</code> variable — an <code>int</code> literal passed straight to a <code>long</code> parameter is zero-extended.

The loader is opened <strong>at run time</strong> by <code>Vk.open()</code>, never linked: <code>vulkan-1.dll</code> on Windows, <code>libvulkan.1.dylib</code> (the LunarG loader and MoltenVK) on macOS — beside the executable, in the library paths, or under <code>$VULKAN_SDK</code>. It returns 0 on a machine without Vulkan, and the program carries on; <code>Vk.has(name)</code> says whether one command is there. Using <code>Vk.*</code> links the generated thunks and the loader; a program that does not is unchanged. See <code>examples/rendering/vk_probe.ludic</code> (what a machine's Vulkan can do) and <code>vk_compute.ludic</code> (a Slang compute shader, dispatched and read back).

```ludic
program Probe {
  property Marker { on: int = 1 }
  model Anchor { Marker }
  handler Boot phase Start {
    spawn Anchor {}
    if Vk.open() == 0 { print("no Vulkan here");  quit() }
    let app = bytes(VkApplicationInfo_sizeof)
    Vk.zero(app, VkApplicationInfo_sizeof)
    Vk.put_i32(app, VkApplicationInfo_sType, VK_STRUCTURE_TYPE_APPLICATION_INFO)
    Vk.put_i32(app, VkApplicationInfo_apiVersion, (1 << 22) | (3 << 12))
    let ci = bytes(VkInstanceCreateInfo_sizeof)
    Vk.zero(ci, VkInstanceCreateInfo_sizeof)
    Vk.put_i32(ci, VkInstanceCreateInfo_sType, VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO)
    Vk.put_ptr(ci, VkInstanceCreateInfo_pApplicationInfo, app)
    let out = bytes(8)
    if Vk.create_instance(ci, null, out) == VK_SUCCESS {
      print("a Vulkan instance")
      Vk.destroy_instance(Vk.get_ptr(out, 0), null)
    }
    quit()
  }
}
```