gl_FrontFacing — indicates whether a primitive is front or back facing
in bool gl_FrontFacing ;
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:
where
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.
| OpenGL Shading Language Version | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Variable Name | 1.10 | 1.20 | 1.30 | 1.40 | 1.50 | 3.30 | 4.00 | 4.10 | 4.20 | 4.30 | 4.40 | 4.50 |
| gl_FrontFacing | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
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/.