VK_EXT_fragment_density_map2(3)

# VK_EXT_fragment_density_map2(3) Manual Page

## Name

VK_EXT_fragment_density_map2 - device extension

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## Registered Extension Number

333

## Revision

1

## Extension and Version Dependencies

VK_EXT_fragment_density_map

## Contact

- Matthew Netsch mnetsch

## Other Extension Metadata

Last Modified Date

  2020-06-16

Interactions and External Dependencies

  - Interacts with Vulkan 1.1

Contributors

  - Matthew Netsch, Qualcomm Technologies, Inc.

  - Jonathan Tinkham, Qualcomm Technologies, Inc.

  - Jonathan Wicks, Qualcomm Technologies, Inc.

  - Jan-Harald Fredriksen, ARM

## Description

This extension adds additional features and properties to `VK_EXT_fragment_density_map` in order to reduce fragment density map host latency as well as improved queries for subsampled sampler implementation-dependent behavior.

## New Structures

- Extending VkPhysicalDeviceFeatures2, VkDeviceCreateInfo:

  - VkPhysicalDeviceFragmentDensityMap2FeaturesEXT

- Extending VkPhysicalDeviceProperties2:

  - VkPhysicalDeviceFragmentDensityMap2PropertiesEXT

## New Enum Constants

- `VK_EXT_FRAGMENT_DENSITY_MAP_2_EXTENSION_NAME`

- `VK_EXT_FRAGMENT_DENSITY_MAP_2_SPEC_VERSION`

- Extending VkImageViewCreateFlagBits:

  - `VK_IMAGE_VIEW_CREATE_FRAGMENT_DENSITY_MAP_DEFERRED_BIT_EXT`

- Extending VkStructureType:

  - `VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_FRAGMENT_DENSITY_MAP_2_FEATURES_EXT`

  - `VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_FRAGMENT_DENSITY_MAP_2_PROPERTIES_EXT`

## Examples

### Additional limits for subsampling

Some implementations may not support subsampled samplers if certain implementation limits are not observed by the app. VkPhysicalDeviceFragmentDensityMap2PropertiesEXT provides additional limits to require apps remain within these boundaries if they wish to use subsampling.

### Improved host latency

By default, the fragment density map is locked by the host for reading between vkCmdBeginRenderPass during recording and `VK_PIPELINE_STAGE_FRAGMENT_DENSITY_PROCESS_BIT_EXT` during draw execution.

This can introduce large latency for certain use cases between recording the frame and displaying the frame. Apps may wish to modify the fragment density map just before draw execution.

`VK_IMAGE_VIEW_CREATE_FRAGMENT_DENSITY_MAP_DEFERRED_BIT_EXT` is intended to help address this for implementations that do not support the `fragmentDensityMapDynamic` feature by deferring the start of the locked range to vkEndCommandBuffer.

    // Create view for fragment density map
    VkImageViewCreateInfo createInfo =
    {
       VK_STRUCTURE_TYPE_IMAGE_VIEW_CREATE_INFO,
       // ...
       VK_IMAGE_VIEW_CREATE_FRAGMENT_DENSITY_MAP_DEFERRED_BIT_EXT,
       fdmImage, // Created with VK_IMAGE_USAGE_FRAGMENT_DENSITY_MAP_BIT_EXT
       // ...
    };

    // ...

    // Begin fragment density map render pass with deferred view.
    // By default, fdmImage must not be modified after this call
    // unless view is created with the FDM dynamic or deferred flags.
    vkCmdBeginRenderPass(commandBuffer, pRenderPassBegin, contents);

    // ...

    vkCmdEndRenderPass(VkCommandBuffer commandBuffer);

    // Can keep making modifications to deferred fragment density maps
    // while recording commandBuffer ...

    result = vkEndCommandBuffer(commandBuffer);

    // Must now freeze modifying fdmImage until after the
    // VK_PIPELINE_STAGE_FRAGMENT_DENSITY_PROCESS_BIT_EXT of
    // the last executing draw that uses the fdmImage in the
    // last submit of commandBuffer.

## Version History

- Revision 1, 2020-06-16 (Matthew Netsch)

  - Initial version

## See Also

VkPhysicalDeviceFragmentDensityMap2FeaturesEXT, VkPhysicalDeviceFragmentDensityMap2PropertiesEXT

## 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.

## Copyright

Copyright 2014-2023 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0