NAME

       fwidth - return the sum of the absolute value of derivatives in x and y

DECLARATION

       genType fwidth(genType p);

       genType fwidthCoarse(genType p);

       genType fwidthFine(genType p);

PARAMETERS

       p
           Specifies the expression of which to take the partial derivative.

DESCRIPTION

       Available only in the fragment shader, these functions return the sum of the absolute
       derivatives in $x$ and $y$ using local differencing for the input argument p.  fwidth is
       equivalent to abs(dFdx(p)) + abs(dFdy(p)).  fwidthCoarse is equivalent to
       abs(dFdxCoarse(p)) + abs(dFdyCoarse(p)).  fwidthFine is equivalent to abs(dFdxFine(p)) +
       abs(dFdyFine(p)).

VERSION SUPPORT

       ┌──────────────┬───────────────────────────────────────────────────────────────────────────────────┐
       │              │        OpenGL Shading Language Version                                            │
       ├──────────────┼──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┤
       │Function      │ 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          │      │      │      │      │      │      │      │      │      │      │      │      │
       ├──────────────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┤
       │fwidth        │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │
       ├──────────────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┤
       │fwidthCoarse, │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  ✔   │
       │fwidthFine    │      │      │      │      │      │      │      │      │      │      │      │      │
       └──────────────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┘

SEE ALSO

       dFdx()

COPYRIGHT

       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

       Copyright © 2011-2014 Khronos Group

[FIXME: source]                             07/22/2015                                 FWIDTH(3G)