[[VK_NV_external_memory]]
== VK_NV_external_memory

*Name String*::
    +VK_NV_external_memory+
*Extension Type*::
    Device extension
*Registered Extension Number*::
    57
*Status*::
    Complete
*Last Modified Date*::
    2016-08-19
*Revision*::
    1
*IP Status*::
    No known IP claims.
*Dependencies*::
    - This extension is written against version 1.0 of the Vulkan API.
    - Requires +VK_NV_external_memory_capabilities+
*Contributors*::
    - James Jones, NVIDIA
    - Carsten Rohde, NVIDIA
*Contact*::
    - James Jones (jajones 'at' nvidia.com)

Applications may wish to export memory to other Vulkan instances or other
APIs, or import memory from other Vulkan instances or other APIs to enable
Vulkan workloads to be split up across application module, process, or API
boundaries.
This extension enables applications to create exportable Vulkan memory
objects such that the underlying resources can be referenced outside the
Vulkan instance that created them.

=== New Object Types

None.

=== New Enum Constants

Extending elink:VkStructureType:

  ** ename:VK_STRUCTURE_TYPE_EXTERNAL_MEMORY_IMAGE_CREATE_INFO_NV
  ** ename:VK_STRUCTURE_TYPE_EXPORT_MEMORY_ALLOCATE_INFO_NV

=== New Enums

None.

=== New Structures

  * Extending slink:VkImageCreateInfo:
  ** slink:VkExternalMemoryImageCreateInfoNV
  * Extending slink:VkMemoryAllocateInfo
  ** slink:VkExportMemoryAllocateInfoNV

=== New Functions

None.

=== Issues

1) If memory objects are shared between processes and APIs, is this
    considered aliasing according to the rules outlined in section 11.8,
    Memory Aliasing?

    RESOLUTION: Yes, but strict exceptions to the rules are added to allow
    some forms of aliasing in these cases.
    Further, other extensions may build upon these new aliasing rules to
    define specific support usage within Vulkan for imported native memory
    objects, or memory objects from other APIs.

2) Are new image layouts or metadata required to specify image layouts and
    layout transitions compatible with non-Vulkan APIs, or with other
    instances of the same Vulkan driver?

    RESOLUTION: No.
    Separate instances of the same Vulkan driver running on the same GPU
    should have identical internal layout semantics, so applictions have the
    tools they need to ensure views of images are consistent between the two
    instances.
    Other APIs will fall into two categories: Those that are Vulkan-
    compatible (A term to be defined by subsequent interopability
    extensions), or Vulkan incompatible.
    When sharing images with Vulkan incompatible APIs, the Vulkan image must
    be transitioned to the GENERAL layout before handing it off to the
    external API.

    Note this does not attempt to address cross-device transitions, nor
    transitions to engines on the same device which are not visible within
    the Vulkan API.
    Both of these are beyond the scope of this extension.

=== Examples

[source,{basebackend@docbook:c++:cpp}]
----------------------------------------

    // TODO: Write some sample code here.

----------------------------------------

=== Version History

  * Revision 1, 2016-08-19 (James Jones)
    - Initial draft