Safe Haskell	None
Language	Haskell2010

Vulkan.Extensions.VK_KHR_maintenance2

Description

Name

VK_KHR_maintenance2 - device extension

VK_KHR_maintenance2

Name String: VK_KHR_maintenance2

Extension Type

Device extension

Registered Extension Number

118

Revision

1

Extension and Version Dependencies

Requires Vulkan 1.0

Deprecation state

Promoted to Vulkan 1.1

Contact

Michael Worcester @michaelworcester%0A<<Here describe the issue or question you have about the VK_KHR_maintenance2 extension> >

Other Extension Metadata

Last Modified Date: 2017-09-05

Interactions and External Dependencies

Promoted to Vulkan 1.1 Core

Contributors

Michael Worcester, Imagination Technologies
Stuart Smith, Imagination Technologies
Jeff Bolz, NVIDIA
Daniel Koch, NVIDIA
Jan-Harald Fredriksen, ARM
Daniel Rakos, AMD
Neil Henning, Codeplay
Piers Daniell, NVIDIA

Description

VK_KHR_maintenance2 adds a collection of minor features that were intentionally left out or overlooked from the original Vulkan 1.0 release.

The new features are as follows:

Allow the application to specify which aspect of an input attachment might be read for a given subpass.
Allow implementations to express the clipping behavior of points.
Allow creating images with usage flags that may not be supported for the base image’s format, but are supported for image views of the image that have a different but compatible format.
Allow creating uncompressed image views of compressed images.
Allow the application to select between an upper-left and lower-left origin for the tessellation domain space.
Adds two new image layouts for depth stencil images to allow either the depth or stencil aspect to be read-only while the other aspect is writable.

Input Attachment Specification

Input attachment specification allows an application to specify which aspect of a multi-aspect image (e.g. a combined depth stencil format) will be accessed via a subpassLoad operation.

On some implementations there may be a performance penalty if the implementation does not know (at createRenderPass time) which aspect(s) of multi-aspect images can be accessed as input attachments.

Promotion to Vulkan 1.1

All functionality in this extension is included in core Vulkan 1.1, with the KHR suffix omitted. The original type, enum and command names are still available as aliases of the core functionality.

New Structures

InputAttachmentAspectReferenceKHR

Extending ImageViewCreateInfo:
- ImageViewUsageCreateInfoKHR
Extending PhysicalDeviceProperties2:
- PhysicalDevicePointClippingPropertiesKHR
Extending PipelineTessellationStateCreateInfo:
- PipelineTessellationDomainOriginStateCreateInfoKHR
Extending RenderPassCreateInfo:
- RenderPassInputAttachmentAspectCreateInfoKHR

New Enums

PointClippingBehaviorKHR

TessellationDomainOriginKHR

New Enum Constants

KHR_MAINTENANCE_2_EXTENSION_NAME

Input Attachment Specification Example

Consider the case where a render pass has two subpasses and two attachments.

Attachment 0 has the format FORMAT_D24_UNORM_S8_UINT, attachment 1 has some color format.

Subpass 0 writes to attachment 0, subpass 1 reads only the depth information from attachment 0 (using inputAttachmentRead) and writes to attachment 1.

    VkInputAttachmentAspectReferenceKHR references[] = {
        {
            .subpass = 1,
            .inputAttachmentIndex = 0,
            .aspectMask = VK_IMAGE_ASPECT_DEPTH_BIT
        }
    };

    VkRenderPassInputAttachmentAspectCreateInfoKHR specifyAspects = {
        .sType = VK_STRUCTURE_TYPE_RENDER_PASS_INPUT_ATTACHMENT_ASPECT_CREATE_INFO_KHR,
        .pNext = NULL,
        .aspectReferenceCount = 1,
        .pAspectReferences = references
    };


    VkRenderPassCreateInfo createInfo = {
        ...
        .pNext = &specifyAspects,
        ...
    };

    vkCreateRenderPass(...);

Issues

1) What is the default tessellation domain origin?

RESOLVED: Vulkan 1.0 originally inadvertently documented a lower-left origin, but the conformance tests and all implementations implemented an upper-left origin. This extension adds a control to select between lower-left (for compatibility with OpenGL) and upper-left, and we retroactively fix unextended Vulkan to have a default of an upper-left origin.