75 lines
2.2 KiB
Plaintext
75 lines
2.2 KiB
Plaintext
// Copyright (c) 2014-2016 Khronos Group. This work is licensed under a
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// Creative Commons Attribution 4.0 International License; see
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// http://creativecommons.org/licenses/by/4.0/
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VkFrontFace(3)
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==============
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Name
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----
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VkFrontFace - interpret polygon front-facing orientation
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C Specification
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---------------
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// refBegin VkFrontFace interpret polygon front-facing orientation
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The first step of polygon rasterization is to determine whether the triangle
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is _back-facing_ or _front-facing_. This determination is made based on the
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sign of the (clipped or unclipped) polygon's area computed in framebuffer
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coordinates. One way to compute this area is:
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[latexmath]
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++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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\[
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a = -{1 \over 2}\sum_{i=0}^{n-1}
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x_f^i y_f^{i \oplus 1} -
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x_f^{i \oplus 1} y_f^i
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\]
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++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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where latexmath:[$x_f^i$] and latexmath:[$y_f^i$] are the latexmath:[$x$]
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and latexmath:[$y$] framebuffer coordinates of the latexmath:[$i$]th vertex
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of the latexmath:[$n$]-vertex polygon (vertices are numbered starting at
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zero for the purposes of this computation) and latexmath:[$i \oplus 1$] is
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latexmath:[$(i + 1)~ \textrm{mod}~ n$].
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The interpretation of the sign of latexmath:[$a$]
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is determined by the
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slink:VkPipelineRasterizationStateCreateInfo::pname:frontFace property of
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the currently active pipeline, which takes the following values:
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include::../api/enums/VkFrontFace.txt[]
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Description
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-----------
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If pname:frontFace is set to ename:VK_FRONT_FACE_COUNTER_CLOCKWISE, a triangle with
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positive area is considered front-facing. If it is set to
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ename:VK_FRONT_FACE_CLOCKWISE, a triangle with negative area is considered
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front-facing. Any triangle which is not front-facing is back-facing,
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including zero-area triangles.
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// refEnd VkFrontFace
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See Also
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--------
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slink:VkPipelineRasterizationStateCreateInfo
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Document Notes
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--------------
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For more information, see the Vulkan Specification at URL
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https://www.khronos.org/registry/vulkan/specs/1.0/xhtml/vkspec.html#VkFrontFace
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This page is extracted from the Vulkan Specification.
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Fixes and changes should be made to the Specification,not directly.
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include::footer.txt[]
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