251

1

## 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 color sample coverage from the pixel coverage. This extension defines the following modes to control how this reduction is performed.

• Merge: When there are more samples in the pixel coverage than color samples, there is an implementation dependent association of each pixel coverage sample to a color sample. In the merge mode, the color sample coverage is computed such that only if any associated sample in the pixel coverage is covered, the color sample is covered. 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; 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.

### New Enum Constants

• VK_NV_COVERAGE_REDUCTION_MODE_EXTENSION_NAME

• VK_NV_COVERAGE_REDUCTION_MODE_SPEC_VERSION

• Extending VkStructureType:

• VK_STRUCTURE_TYPE_FRAMEBUFFER_MIXED_SAMPLES_COMBINATION_NV

• VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_COVERAGE_REDUCTION_MODE_FEATURES_NV

• VK_STRUCTURE_TYPE_PIPELINE_COVERAGE_REDUCTION_STATE_CREATE_INFO_NV

### Version History

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

• Internal revisions