gl_triangle(3) Svgalib User Manual gl_triangle(3)NAMEgl_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 inter‐
preted 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_trisetcolorlookup(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 com‐
binations.
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 threeD‐
kit/ 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 distribution from
the net. Yo don't need to install it. Just make in the threeDkit/ sub‐
directory. As of this writing, svgalib-1.2.12.tar.gz is the latest ver‐
sion 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 mirrored 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 program.
SEE ALSOvgagl(7), svgalib(7), threedkit(7), gl_striangle(3), gl_swtriangle(3),
gl_trigetcolorlookup(3), gl_trisetcolorlookup(3), gl_trisetdraw‐
point(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 gl_triangle(3)
