gl_triangle(3)         Svgalib User Manual         gl_triangle(3)

NAME
       gl_triangle - draw a triangle with interpolated colors

SYNOPSIS
       #include <triangle.h>

       void  gl_triangle(int x0, int y0, int z0, int x1, int y1 ,
       int z1, int x2, int y2, int z2, int bf);

DESCRIPTION
       Draws a triangle between the three points 0, 1 and 2.

       z0, z1 and z2 are the colors at those  points.  Hence,  if
       you set the palette to a grayscale, the triangle will have
       an interpolated gray shade.

       If you are using more than 8 bit color, the z values  will
       be  interpreted  as  an index to a lookup table of at most
       4096 entries long. Each entry is of type long.

       You can set the entries with the function  gl_trisetcolor-
       lookup(3).

       The  bf  value is used to tell the routine not to draw the
       triangle if it is facing the other way.   bf  tells  which
       way  the triangle should be facing to be drawn.  since you
       will more than likely require both combinations.

       bf = 0 disables  drawing  when  the  points  are  arranged
       clockwise,  bf  =  1  disables drawing when the points are
       arranged counter clockwise.  bf = -1 will probably  always
       draw the triangle.

       Beware,  these  functions  are  not  a  direct part of the
       svgalib library.  Instead their source is part of  svgalib
       and  can  be  found  in the threeDkit/ subdirectory of the
       original  svgalib  distribution.  However,   it   is   not
       installed  in  the  system  by default, s.t. it is unclear
       where you can find it if your  svgalib  was  installed  by
       some linux distribution.

       In case of any such problem, simply get an svgalib distri-
       bution from the net. Yo don't need  to  install  it.  Just
       make  in  the threeDkit/ subdirectory. As of this writing,
       svgalib-1.2.12.tar.gz is the latest  version  and  can  be
       retrieved     by     ftp     from    sunsite.unc.edu    at
       /pub/Linux/libs/graphics     and     tsx-11.mit.edu     at
       /pub/linux/sources/libs  which  will most probably be mir-
       rored by a site close to you.

       The functions are defined in the tri.o and triangl.o files
       (or  their resp. sources) which you must link to your pro-
       gram.

SEE ALSO
       vgagl(7),   svgalib(7),   threedkit(7),   gl_striangle(3),
       gl_swtriangle(3), gl_trigetcolorlookup(3), gl_trisetcolor-
       lookup(3),     gl_trisetdrawpoint(3),     gl_wtriangle(3),
       plane(6), wrapdemo(6).

AUTHOR
       This manual page was edited by Michael Weller <eowmob@exp-
       math.uni-essen.de>. The demos, the  initial  documentation
       and  the  whole  threedkit  stuff  was  done by Paul Sheer
       <psheer@icon.co.za>.

       Paper mail:
              Paul Sheer
              P O BOX 890507
              Lyndhurst
              Johannesburg 2106
              South Africa

       Donations (by check or postal order) will  be  appreciated
       and  will  encourage further development of this software.
       However this is strictly on a voluntary basis  where  this
       software  falls  under  the  GNU  LIBRARY  GENERAL  PUBLIC
       LICENSE.

Svgalib (>= 1.2.11)         2 Aug 1997                          1