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## Extension and Version Dependencies

• Requires Vulkan 1.0

• Requires VK_NV_framebuffer_mixed_samples

2019-01-29

Contributors
• Kedarnath Thangudu, NVIDIA

• Jeff Bolz, NVIDIA

### Description

When using a framebuffer with mixed samples, a per-fragment coverage reduction operation is performed which generates a color sample mask from the coverage mask. This extension defines the following modes to control how this reduction is performed.

• Merge: When there are more raster samples than color samples, there is an implementation dependent association of each raster sample to a color sample. In the merge mode, the reduced color sample mask is computed such that the bit for each color sample is 1 if any of the associated bits in the fragment’s coverage is on, and 0 otherwise. This is the default mode.

• Truncate: When there are more raster samples (N) than color samples(M), there is one to one association of the first M raster samples to the M color samples and the coverage bits for the other raster samples are ignored.

When the number of raster samples is equal to the color samples, there is a one to one mapping between them in either of the above modes.

The new command vkGetPhysicalDeviceSupportedFramebufferMixedSamplesCombinationsNV can be used to query the various raster, color, depth/stencil sample count and reduction mode combinations that are supported by the implementation. This extension would allow an implementation to support the behavior of both VK_NV_framebuffer_mixed_samples and VK_AMD_mixed_attachment_samples extensions simultaneously.

None.

### New Enum Constants

• Extending VkStructureType

• VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_COVERAGE_REDUCTION_MODE_FEATURES_NV

• VK_STRUCTURE_TYPE_PIPELINE_COVERAGE_REDUCTION_STATE_CREATE_INFO_NV

• VK_STRUCTURE_TYPE_FRAMEBUFFER_MIXED_SAMPLES_COMBINATION_NV

None.

### Version History

• Revision 1, 2019-01-29 (Kedarnath Thangudu)

• Internal revisions