Name

VK_KHR_incremental_present - device extension

VK_KHR_incremental_present

Name String

VK_KHR_incremental_present

Extension Type

Device extension

Registered Extension Number

85

Revision

2

Ratification Status

Ratified

Extension and Version Dependencies

VK_KHR_swapchain

Contact

• Ian Elliott @ianelliottus%0A*Here describe the issue or question you have about the VK_KHR_incremental_present extension*

Other Extension Metadata

Last Modified Date

2016-11-02

IP Status

No known IP claims.

Contributors

• Ian Elliott, Google
• Jesse Hall, Google
• Alon Or-bach, Samsung
• James Jones, NVIDIA
• Daniel Rakos, AMD
• Ray Smith, ARM
• Mika Isojarvi, Google
• Jeff Juliano, NVIDIA
• Jeff Bolz, NVIDIA

Description

This device extension extends queuePresentKHR, from the VK_KHR_swapchain extension, allowing an application to specify a list of rectangular, modified regions of each image to present. This should be used in situations where an application is only changing a small portion of the presentable images within a swapchain, since it enables the presentation engine to avoid wasting time presenting parts of the surface that have not changed.

This extension is leveraged from the EGL_KHR_swap_buffers_with_damage extension.

New Structures

• PresentRegionKHR

• RectLayerKHR

• Extending PresentInfoKHR:

  • PresentRegionsKHR

New Enum Constants

• KHR_INCREMENTAL_PRESENT_EXTENSION_NAME

• KHR_INCREMENTAL_PRESENT_SPEC_VERSION

• Extending StructureType:

  • STRUCTURE_TYPE_PRESENT_REGIONS_KHR

Issues

1) How should we handle steroescopic-3D swapchains? We need to add a layer for each rectangle. One approach is to create another struct containing the Rect2D plus layer, and have PresentRegionsKHR point to an array of that struct. Another approach is to have two parallel arrays, pRectangles and pLayers, where pRectangles[i] and pLayers[i] must be used together. Which approach should we use, and if the array of a new structure, what should that be called?

RESOLVED: Create a new structure, which is a Rect2D plus a layer, and will be called RectLayerKHR.

2) Where is the origin of the RectLayerKHR?

RESOLVED: The upper left corner of the presentable image(s) of the swapchain, per the definition of framebuffer coordinates.

3) Does the rectangular region, RectLayerKHR, specify pixels of the swapchain’s image(s), or of the surface?

RESOLVED: Of the image(s). Some presentation engines may scale the pixels of a swapchain’s image(s) to the size of the surface. The size of the swapchain’s image(s) will be consistent, where the size of the surface may vary over time.

4) What if all of the rectangles for a given swapchain contain a width and/or height of zero?

RESOLVED: The application is indicating that no pixels changed since the last present. The presentation engine may use such a hint and not update any pixels for the swapchain. However, all other semantics of queuePresentKHR must still be honored, including waiting for semaphores to signal.

5) When the swapchain is created with SwapchainCreateInfoKHR::preTransform set to a value other than SURFACE_TRANSFORM_IDENTITY_BIT_KHR, should the rectangular region, RectLayerKHR, be transformed to align with the preTransform?

RESOLVED: No. The rectangular region in RectLayerKHR should not be transformed. As such, it may not align with the extents of the swapchain’s image(s). It is the responsibility of the presentation engine to transform the rectangular region. This matches the behavior of the Android presentation engine, which set the precedent.

Version History

• Revision 1, 2016-11-02 (Ian Elliott)

  • Internal revisions

• Revision 2, 2021-03-18 (Ian Elliott)

  • Clarified alignment of rectangles for presentation engines that support transformed swapchains.

See Also

PresentRegionKHR, PresentRegionsKHR, RectLayerKHR

Document Notes

For more information, see the Vulkan Specification

This page is a generated document. Fixes and changes should be made to the generator scripts, not directly.