92 lines
2.9 KiB
Plaintext
92 lines
2.9 KiB
Plaintext
[[VK_NV_framebuffer_mixed_samples]]
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== VK_NV_framebuffer_mixed_samples
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*Name String*::
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VK_NV_framebuffer_mixed_samples
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*Extension Type*::
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Device extension
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*Registered Extension Number*::
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153
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*Status*::
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Complete
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*Last Modified Data*::
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2017-06-04
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*Revision*::
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1
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*Dependencies*::
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- This extension is written against version 1.0 of the Vulkan API.
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- This extension requires Vulkan 1.0.
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*Contributors*::
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*Contact*::
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- Jeff Bolz (jbolz 'at' nvidia.com)
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This extension allows multisample rendering with a raster and depth/stencil
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sample count that is larger than the color sample count.
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Rasterization and the results of the depth and stencil tests together
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determine the portion of a pixel that is "covered".
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It can be useful to evaluate coverage at a higher frequency than color
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samples are stored.
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This coverage is then "reduced" to a collection of covered color samples,
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each having an opacity value corresponding to the fraction of the color
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sample covered.
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The opacity can optionally be blended into individual color samples.
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Rendering with fewer color samples than depth/stencil samples greatly
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reduces the amount of memory and bandwidth consumed by the color buffer.
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However, converting the coverage values into opacity introduces artifacts
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where triangles share edges and may: not be suitable for normal triangle
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mesh rendering.
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One expected use case for this functionality is Stencil-then-Cover path
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rendering (similar to the OpenGL GL_NV_path_rendering extension).
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The stencil step determines the coverage (in the stencil buffer) for an
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entire path at the higher sample frequency, and then the cover step draws
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the path into the lower frequency color buffer using the coverage
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information to antialias path edges.
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With this two-step process, internal edges are fully covered when
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antialiasing is applied and there is no corruption on these edges.
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The key features of this extension are:
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* It allows render pass and framebuffer objects to be created where the
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number of samples in the depth/stencil attachment in a subpass is a
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multiple of the number of samples in the color attachments in the
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subpass.
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* A coverage reduction step is added to Fragment Operations which converts
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a set of covered raster/depth/stencil samples to a set of color samples
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that perform blending and color writes.
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The coverage reduction step also includes an optional coverage modulation
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step, multiplying color values by a fractional opacity corresponding to
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the number of associated raster/depth/stencil samples covered.
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=== New Object Types
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None.
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=== New Enum Constants
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None.
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=== New Enums
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* elink:VkCoverageModulationModeNV
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* elink:VkPipelineCoverageModulationStateCreateFlagsNV
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=== New Structures
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* slink:VkPipelineCoverageModulationStateCreateInfoNV
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=== New Functions
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None.
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=== Issues
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None.
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=== Version History
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* Revision 1, 2017-06-04 (Jeff Bolz)
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- Internal revisions
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