VK_KHR_maintenance2
Other Extension Metadata
Last Modified Date
2017-09-05
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 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 vkCreateRenderPass 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
- VkInputAttachmentAspectReferenceKHR
- Extending VkImageViewCreateInfo:
- Extending VkPhysicalDeviceProperties2:
- Extending VkPipelineTessellationStateCreateInfo:
- Extending VkRenderPassCreateInfo:
New Enums
New Enum Constants
VK_KHR_MAINTENANCE2_EXTENSION_NAME
VK_KHR_MAINTENANCE2_SPEC_VERSION
VK_KHR_MAINTENANCE_2_EXTENSION_NAME
VK_KHR_MAINTENANCE_2_SPEC_VERSION
- Extending VkImageCreateFlagBits:
VK_IMAGE_CREATE_BLOCK_TEXEL_VIEW_COMPATIBLE_BIT_KHR
VK_IMAGE_CREATE_EXTENDED_USAGE_BIT_KHR
- Extending VkImageLayout:
VK_IMAGE_LAYOUT_DEPTH_ATTACHMENT_STENCIL_READ_ONLY_OPTIMAL_KHR
VK_IMAGE_LAYOUT_DEPTH_READ_ONLY_STENCIL_ATTACHMENT_OPTIMAL_KHR
- Extending VkPointClippingBehavior:
VK_POINT_CLIPPING_BEHAVIOR_ALL_CLIP_PLANES_KHR
VK_POINT_CLIPPING_BEHAVIOR_USER_CLIP_PLANES_ONLY_KHR
- Extending VkStructureType:
VK_STRUCTURE_TYPE_IMAGE_VIEW_USAGE_CREATE_INFO_KHR
VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_POINT_CLIPPING_PROPERTIES_KHR
VK_STRUCTURE_TYPE_PIPELINE_TESSELLATION_DOMAIN_ORIGIN_STATE_CREATE_INFO_KHR
VK_STRUCTURE_TYPE_RENDER_PASS_INPUT_ATTACHMENT_ASPECT_CREATE_INFO_KHR
- Extending VkTessellationDomainOrigin:
VK_TESSELLATION_DOMAIN_ORIGIN_LOWER_LEFT_KHR
VK_TESSELLATION_DOMAIN_ORIGIN_UPPER_LEFT_KHR
Input Attachment Specification Example
Consider the case where a render pass has two subpasses and two attachments.
Attachment 0 has the format VK_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.
Version History
- Revision 1, 2017-04-28