.TH gl_wtriangle 3 "2 Aug 1997" "Svgalib (>= 1.2.11)" "Svgalib User Manual"
.SH NAME
gl_wtriangle \- draw a shadowed pixmap mapped on a triangle

.SH SYNOPSIS
.B #include <triangle.h>

.B typedef struct {
.br
.BI "    unsigned char *" bitmap1 ;
.br
.BI "    unsigned char *" bitmap2 ;
.br
.BI "    int " bf ;
.br
.BI "} " TD_tridata ;

.BI "void gl_wtriangle(int " x0 ", int " y0 ", int " xd0 ", int " yd0 ", int " z0
.BI ", int " x1 ", int " y1 ", int " xd1 ", int " yd1 ", int " z1
.BI ", int " x2 ", int " y2 ", int " xd2 ", int " yd2 ", int " z2 ", TD_tridata *" tri );

.SH DESCRIPTION
Draws a triangle at points 0, 1, 2 by mapping the pixmaps defined
in the
.B TD_triangle
structure into the triangle.

The
.IR xd " and " yd
values represent the triangle on the
bitmap and the
.IR x " and " y
values represent the triangle
on the screen. The
.I z
values represent an additional
value which will be added to the color that is looked
up from the pixmap data. Once again, if the
current context is more than 8 bits then the result
is interpreted as an index to the same lookup table. See
.BR gl_triangle (3)
for more details on shadowing.

.B gl_wtriangle
is used to draw wrapped surfaces
.B with
shadowing interpolation. The function
.BR gl_swtriangle (3)
does it without shadowing.

.I bitmap1
defines the back side of the triangle,
.I bitmap2
the front.

The
.I bf
value is used to tell the routine to draw the backside
if it is facing the other way.
.I bf
tells
which way the triangle should be facing to show the front,
since you will more than likely require both
combinations.

.IB bf " = 2"
defines the back to be drawn when the points are arranged clockwise,
.IB bf " = 3"
defines the back to be drawn when the points are arranged counter clockwise,
.IB bf " = -1"
will probably always draw the front.

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
.I 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 distribution from the net. Yo
don't need to install it. Just
.B make
in the
.I threeDkit/
subdirectory. As of this writing,
.I svgalib-1.2.12.tar.gz
is the latest version and can be retrieved by ftp from
.IR "sunsite.unc.edu" " at " "/pub/Linux/libs/graphics"
and
.IR "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
.IR tri.o " and " triangl.o
files (or their resp. sources) which you must link to your program.

.SH SEE ALSO
.BR vgagl (7),
.BR svgalib (7),
.BR threedkit (7),
.BR gl_striangle (3),
.BR gl_swtriangle (3),
.BR gl_triangle (3),
.BR gl_trigetcolorlookup (3),
.BR gl_trisetcolorlookup (3),
.BR gl_trisetdrawpoint (3),
.BR plane (6),
.BR wrapdemo (6).

.SH 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:
.RS
Paul Sheer
.br
P O BOX 890507
.br
Lyndhurst
.br
Johannesburg 2106
.br
South Africa
.RE

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.