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
Variable | Version 1.10 | Version 1.20 | Version 1.30 | Version 1.40 | Version 1.50 | Version 3.30 | Version 4.00 | Version 4.10 |
---|---|---|---|---|---|---|---|---|
gl_FrontFacing | Y | Y | Y | Y | Y | Y | Y | Y |
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