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)