Name

VK_EXT_legacy_dithering - device extension

VK_EXT_legacy_dithering

Name String

VK_EXT_legacy_dithering

Extension Type

Device extension

Registered Extension Number

466

Revision

1

Ratification Status

Not ratified

Extension and Version Dependencies

VK_KHR_get_physical_device_properties2

Special Use

• OpenGL / ES support

Contact

• Shahbaz Youssefi @syoussefi%0A*Here describe the issue or question you have about the VK_EXT_legacy_dithering extension*

Extension Proposal

VK_EXT_legacy_dithering

Other Extension Metadata

Last Modified Date

2022-03-31

Contributors

• Shahbaz Youssefi, Google
• Graeme Leese, Broadcom
• Jan-Harald Fredriksen, Arm

Description

This extension exposes a hardware feature used by some vendors to implement OpenGL’s dithering. The purpose of this extension is to support layering OpenGL over Vulkan, by allowing the layer to take advantage of the same hardware feature and provide equivalent dithering to OpenGL applications.

New Structures

• Extending PhysicalDeviceFeatures2, DeviceCreateInfo:

  • PhysicalDeviceLegacyDitheringFeaturesEXT

New Enum Constants

• EXT_LEGACY_DITHERING_EXTENSION_NAME

• EXT_LEGACY_DITHERING_SPEC_VERSION

• Extending StructureType:

  • STRUCTURE_TYPE_PHYSICAL_DEVICE_LEGACY_DITHERING_FEATURES_EXT

• Extending SubpassDescriptionFlagBits:

  • SUBPASS_DESCRIPTION_ENABLE_LEGACY_DITHERING_BIT_EXT

If VK_KHR_dynamic_rendering is supported:

• Extending RenderingFlagBits:

  • RENDERING_ENABLE_LEGACY_DITHERING_BIT_EXT

If Version 1.3 is supported:

• Extending RenderingFlagBits:

  • RENDERING_ENABLE_LEGACY_DITHERING_BIT_EXT

Version History

• Revision 1, 2022-03-31 (Shahbaz Youssefi)

  • Internal revisions

Issues

1) In OpenGL, the dither state can change dynamically. Should this extension add a pipeline state for dither?

RESOLVED: No. Changing dither state is rarely, if ever, done during rendering. Every surveyed Android application either entirely disables dither, explicitly enables it, or uses the default state (which is enabled). Additionally, on some hardware dither can only be specified in a render pass granularity, so a change in dither state would necessarily need to cause a render pass break. This extension considers dynamic changes in OpenGL dither state a theoretical situation, and expects the layer to break the render pass in such a situation without any practical downsides.

See Also

PhysicalDeviceLegacyDitheringFeaturesEXT

Document Notes

For more information, see the Vulkan Specification

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