bionic (3) gl_FrontFacing.3G.gz

Provided by: opengl-4-man-doc_1.0~svn33624-1_all bug

NAME
       gl_FrontFacing - indicates whether a primitive is front or back facing


DECLARATION
       in bool gl_FrontFacing ;.SH "DESCRIPTION"

       Available only in the fragment language, gl_FrontFacing is an input variable whose value is true if the
       fragment belongs to a front-facing primitive and false otherwise. The determination of whether a triangle
       primitive is front-facing is made by examining the sign of the area of the triangle, including a possible
       reversal of this sign as controlled by glFrontFace. One way to compute this area is:

       a=12 ∑ j=0 n-1 x w i y w i+1 - x w i+1 y w i

       where x w i and y w i are the x and y window coordinates of the ith vertex of the n-vertex polygon.

       The sign of this computation is negated when the value of GL_CLIP_ORIGIN (the clip volume origin, set
       with glClipControl()) is GL_UPPER_LEFT.


VERSION SUPPORT
       ┌───────────────┬───────────────────────────────────────────────────────────────────────────────────┐
       │               │        OpenGL Shading Language Version                                            │
       ├───────────────┼──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┤
       │Variable       │ 1.10 │ 1.20 │ 1.30 │ 1.40 │ 1.50 │ 3.30 │ 4.00 │ 4.10 │ 4.20 │ 4.30 │ 4.40 │ 4.50 │
       │Name           │      │      │      │      │      │      │      │      │      │      │      │      │
       ├───────────────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┤
       │gl_FrontFacing │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │
       └───────────────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┘


SEE ALSO
       gl_FragCoord(), glClipControl()


       Copyright © 2011-2014 Khronos Group. This material may be distributed subject to the terms and conditions
       set forth in the Open Publication License, v 1.0, 8 June 1999.  http://opencontent.org/openpub/.


       Copyright © 2011-2014 Khronos Group

[FIXME: source]                                    01/03/2018                                 GL_FRONTFACING(3G)