
GFORGE  -   Graphical Fractal Forgery                   v0.01   jpb 5/22/95

Generates 16-bit heightfields for POV-Ray, using a high-quality algorithm:
the IFFT of 1/f noise.  Several parameters give you control over the
appearance of the output, which can range from sand to hills to mountains.

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COMPILING:
----------

The program is not fancy and should compile directly under GNU C (gcc),
just unpack the program and type "make". If you use another compiler, edit
the Makefile and swap out "gcc" for "cc" or whatever you use.  If
successful, make will produce the executable "gforge" which you can invoke
without arguments and it should generate a sample landscape file
"output.tga".

DOS users: executable included in ZIP file. Note that you need the included
GO32.EXE file to be present somewhere in your path.


Purpose:
--------

"gforge" uses an inverse-fourier transform on 1/f filtered gaussian white
noise to produce bumpy surfaces that have the appearance of realistic
landscapes. Output is in a 16 bit (8 bit optional) graphic format for
smooth heightfields in raytracers such as POV-Ray. The program is not at
all original with me; see the man page for history. My sole contribution
was addition of 16-bit output.

"gforge" does not produce any immediate graphical images on the screen, it
just writes a file for a raytracer or graphics viewer. Note the the "TGA"
output is physically the standard 24-bit Targa file format but arranged
with the red and green bytes to represent 16-bit grayscale, so a standard
viewer will display it as green-speckled noise. It appears as a smooth
heightfield when imported into POV, however. PGM (Portable Grey Map) (ASCII
variant) is available also, as 0-65535 integers as ascii strings. If you
just want 8-bit output for viewing directly, select PG8 which is a standard
8-bit binary PGM format, which should be compatible with most viewers.  All
the output formats are greyscales; coloring is left up to you.

For more details, see the man page.



	John Beale
	P.O Box 8188
	Stanford CA 94309-8188
--------------------------------------
  email: beale@jumpjibe.stanford.edu
<http://www-leland.stanford.edu/~beale>
