// Copyright (c) 2015-2017 The Khronos Group Inc. // Copyright notice at https://www.khronos.org/registry/speccopyright.html [[initialization]] = Initialization Before using Vulkan, an application must: initialize it by loading the Vulkan commands, and creating a sname:VkInstance object. [[initialization-functionpointers]] == Command Function Pointers // refBegin vkGetInstanceProcAddr Return a function pointer for a command Vulkan commands are not necessarily exposed statically on a platform. Function pointers for all Vulkan commands can: be obtained with the command: include::../api/protos/vkGetInstanceProcAddr.txt[] * pname:instance is the instance that the function pointer will be compatible with, or `NULL` for commands not dependent on any instance. * pname:pName is the name of the command to obtain. fname:vkGetInstanceProcAddr itself is obtained in a platform- and loader- specific manner. Typically, the loader library will export this command as a function symbol, so applications can: link against the loader library, or load it dynamically and look up the symbol using platform-specific APIs. Loaders are encouraged to export function symbols for all other core Vulkan commands as well; if this is done, then applications that use only the core Vulkan commands have no need to use fname:vkGetInstanceProcAddr. The table below defines the various use cases for fname:vkGetInstanceProcAddr and expected return value ("fp" is function pointer) for each case. The returned function pointer is of type tlink:PFN_vkVoidFunction, and must be cast to the type of the command being queried. .vkGetInstanceProcAddr behavior [width="80%",options="header"] |==== | pname:instance | pname:pName | return value | * | `NULL` | undefined | invalid instance | * | undefined | `NULL` | flink:vkEnumerateInstanceExtensionProperties | fp | `NULL` | flink:vkEnumerateInstanceLayerProperties | fp | `NULL` | flink:vkCreateInstance | fp | `NULL` | * (any pname:pName not covered above) | `NULL` | instance | core Vulkan command | fp^1^ | instance | enabled instance extension commands for pname:instance | fp^1^ | instance | available device extension^2^ commands for pname:instance | fp^1^ | instance | * (any pname:pName not covered above) | `NULL` |==== 1:: The returned function pointer must: only be called with a dispatchable object (the first parameter) that is pname:instance or a child of pname:instance. e.g. sname:VkInstance, sname:VkPhysicalDevice, sname:VkDevice, sname:VkQueue, or sname:VkCommandBuffer. 2:: An "`available extension`" is an extension function supported by any of the loader, driver or layer. include::../validity/protos/vkGetInstanceProcAddr.txt[] // refEnd vkGetInstanceProcAddr PFN_vkVoidFunction // refBegin vkGetDeviceProcAddr Return a function pointer for a command In order to support systems with multiple Vulkan implementations comprising heterogeneous collections of hardware and software, the function pointers returned by fname:vkGetInstanceProcAddr may: point to dispatch code, which calls a different real implementation for different sname:VkDevice objects (and objects created from them). The overhead of this internal dispatch can: be avoided by obtaining device-specific function pointers for any commands that use a device or device-child object as their dispatchable object. Such function pointers can: be obtained with the command: include::../api/protos/vkGetDeviceProcAddr.txt[] The table below defines the various use cases for fname:vkGetDeviceProcAddr and expected return value for each case. The returned function pointer is of type tlink:PFN_vkVoidFunction, and must be cast to the type of the command being queried. .vkGetDeviceProcAddr behavior [width="80%",options="header"] |==== | pname:device | pname:pName | return value | `NULL` | * | undefined | invalid device | * | undefined | device | `NULL` | undefined | device | core Vulkan command | fp^1^ | device | enabled extension commands | fp^1^ | device | * (any pname:pName not covered above) | `NULL` |==== 1:: The returned function pointer must: only be called with a dispatchable object (the first parameter) that is pname:device or a child of pname:device. e.g. sname:VkDevice, sname:VkQueue, or sname:VkCommandBuffer. include::../validity/protos/vkGetDeviceProcAddr.txt[] // refEnd vkGetDeviceProcAddr PFN_vkVoidFunction // refBegin PFN_vkVoidFunction Dummy function pointer type returned by queries The definition of tlink:PFN_vkVoidFunction is: include::../api/funcpointers/PFN_vkVoidFunction.txt[] // refEnd PFN_vkVoidFunction vkGetDeviceProcAddr vkGetInstanceProcAddr ifdef::VK_KHR_get_physical_device_properties2[] === Extending Physical Device From Device Extensions When the +VK_KHR_get_physical_device_properties2+ extension is enabled, physical device extension commands and structures can: be used with a physical device if the corresponding extension is enumerated by flink:vkEnumerateDeviceExtensionProperties for that physical device, even before a logical device has been created. To obtain a function pointer for a physical-device command from a device extension, an application can: use fname:vkGetInstanceProcAddr. This function pointer may: point to dispatch code, which calls a different real implementation for different sname:VkPhysicalDevice objects. Behavior is undefined if an extension physical-device command is called on a physical device that doesn't support the extension. Device extensions may: define structures that can: be added to the pNext-chain of physical-device commands. Behavior is undefined if such an extension structure is passed to a physical device command for a physical device that doesn't support the extension. endif::VK_KHR_get_physical_device_properties2[] [[initialization-instances]] == Instances // refBegin VkInstance Opaque handle to a instance object There is no global state in Vulkan and all per-application state is stored in a sname:VkInstance object. Creating a sname:VkInstance object initializes the Vulkan library and allows the application to pass information about itself to the implementation. Instances are represented by sname:VkInstance handles: include::../api/handles/VkInstance.txt[] // refEnd VkInstance // refBegin vkCreateInstance Create a new Vulkan instance To create an instance object, call: include::../api/protos/vkCreateInstance.txt[] * pname:pCreateInfo points to an instance of slink:VkInstanceCreateInfo controlling creation of the instance. * pname:pAllocator controls host memory allocation as described in the <> chapter. * pname:pInstance points a sname:VkInstance handle in which the resulting instance is returned. fname:vkCreateInstance creates the instance, then enables and initializes global layers and extensions requested by the application. If an extension is provided by a layer, both the layer and extension must: be specified at fname:vkCreateInstance time. If a specified layer cannot be found, no sname:VkInstance will be created and the function will return ename:VK_ERROR_LAYER_NOT_PRESENT. Likewise, if a specified extension cannot be found the call will return ename:VK_ERROR_EXTENSION_NOT_PRESENT. include::../validity/protos/vkCreateInstance.txt[] // refBegin VkInstanceCreateInfo Structure specifying parameters of a newly created instance The sname:VkInstanceCreateInfo structure is defined as: include::../api/structs/VkInstanceCreateInfo.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:flags is reserved for future use. * pname:pApplicationInfo is `NULL` or a pointer to an instance of sname:VkApplicationInfo. If not `NULL`, this information helps implementations recognize behavior inherent to classes of applications. slink:VkApplicationInfo is defined in detail below. * pname:enabledLayerCount is the number of global layers to enable. * pname:ppEnabledLayerNames is a pointer to an array of pname:enabledLayerCount null-terminated UTF-8 strings containing the names of layers to enable for the created instance. See the <> section for further details. * pname:enabledExtensionCount is the number of global extensions to enable. * pname:ppEnabledExtensionNames is a pointer to an array of pname:enabledExtensionCount null-terminated UTF-8 strings containing the names of extensions to enable. include::../validity/structs/VkInstanceCreateInfo.txt[] ifdef::VK_EXT_validation_flags[] include::VK_EXT_validation_flags.txt[] endif::VK_EXT_validation_flags[] // refBegin VkApplicationInfo Structure specifying application info The sname:VkApplicationInfo structure is defined as: include::../api/structs/VkApplicationInfo.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:pApplicationName is a pointer to a null-terminated UTF-8 string containing the name of the application. * pname:applicationVersion is an unsigned integer variable containing the developer-supplied version number of the application. * pname:pEngineName is a pointer to a null-terminated UTF-8 string containing the name of the engine (if any) used to create the application. * pname:engineVersion is an unsigned integer variable containing the developer-supplied version number of the engine used to create the application. * pname:apiVersion is the version of the Vulkan API against which the application expects to run, encoded as described in the <> section. If pname:apiVersion is 0 the implementation must: ignore it, otherwise if the implementation does not support the requested pname:apiVersion it must: return ename:VK_ERROR_INCOMPATIBLE_DRIVER. The patch version number specified in pname:apiVersion is ignored when creating an instance object. Only the major and minor versions of the instance must: match those requested in pname:apiVersion. .Valid Usage **** * pname:apiVersion must: be zero, or otherwise it must: be a version that the implementation supports, or supports an effective substitute for **** include::../validity/structs/VkApplicationInfo.txt[] // refBegin vkDestroyInstance Destroy an instance of Vulkan To destroy an instance, call: include::../api/protos/vkDestroyInstance.txt[] * pname:instance is the handle of the instance to destroy. * pname:pAllocator controls host memory allocation as described in the <> chapter. .Valid Usage **** * All child objects created using pname:instance must: have been destroyed prior to destroying pname:instance * If sname:VkAllocationCallbacks were provided when pname:instance was created, a compatible set of callbacks must: be provided here * If no sname:VkAllocationCallbacks were provided when pname:instance was created, pname:pAllocator must: be `NULL` **** include::../validity/protos/vkDestroyInstance.txt[]