gl_wtriangle man page

gl_wtriangle — draw a shadowed pixmap mapped on a triangle

Synopsis

#include <triangle.h>

typedef struct {
unsigned char *bitmap1;
unsigned char *bitmap2;
int bf;
} TD_tridata;

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

Description

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

The xd and yd values represent the triangle on the bitmap and the x and y values represent the triangle on the screen. The 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 gl_triangle(3) for more details on shadowing.

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

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

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

bf = 2 defines the back to be drawn when the points are arranged clockwise, bf = 3 defines the back to be drawn when the points are arranged counter clockwise, 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 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 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 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 Also

vgagl(7), svgalib(7), threedkit(7), gl_striangle(3), gl_swtriangle(3), gl_triangle(3), gl_trigetcolorlookup(3), gl_trisetcolorlookup(3), gl_trisetdrawpoint(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.

Referenced By

gl_striangle(3), gl_swtriangle(3), gl_triangle(3), gl_trisetcolorlookup(3), gl_trisetdrawpoint(3), threedkit(7), vgagl(7).

2 Aug 1997 Svgalib (>= 1.2.11) Svgalib User Manual