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qrt_st.txt
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QRT/ST Machine Specific Reference
Robert Barnhardt
COPYRIGHT INFORMATION
QRT source and executable is Copyright 1988 Steve Koren. It may
be freely copied, modified, and distributed under the following
conditions:
1) Notice of any changes is posted and distributed with
subsequent versions.
2) Neither the source nor executable is sold for profit.
3) This message is distributed unmodified with the source and
executable.
Any images created with QRT are yours to do with as you wish.
INTRODUCTION
The QRT ray tracer was ported from Steve Koren's original Amiga
sources, and thus it should be 100% compatible, the few
exceptions being noted in the remainder of this document.
The general usage of QRT is a simple, 3-step process:
o Create a scene description file (.QRT), in accordance with
the accompanying QRT documentation.
o Render the scene with QRT, to produce a graphical output
image file (.RAW).
o Convert the image to a format displayable on your equipment
(for the ST, Spectrum 512 format).
QRT/ST USAGE
The command line of QRT/ST differs slightly from that of the Amiga
version. Because of the extremely short TTP line, the command
line keywords -aspect, -foclen, -xres, and -yres have been
shortened to -a, -f, -x, and -y, respectively.
Usage: QRT [-x +i] [-y +i] [-a +f] [-f +f] filename.qrt
-x specifies the x resolution of the output file.
-y " " y " " " " " .
-a " " aspect ratio of the output file.
-f " " focal length of the observer.
( Where +i and +f are positive integer and floating point. )
Command line options will override information in the input file.
If you do not specify an input file, QRT/ST will wait for you to
enter a description by hand: to abort, press Control-C; to signal
that your description is complete, press Control-Z.
QRT Ray Tracer Page 1 ST Reference
QRT/ST INPUT FILES
All keywords supported in the current release (1.4) of QRT for the
Amiga are supported, with the exception of DITHER; its inclusion
or exclusion will be completely ignored, generating no errors.
With an output resolution of 16 million colours, dithering (in the
source) is redundant; the rendering of the output image is left
wholly to the post-processor.
In addition to the FIRST_SCAN and LAST_SCAN keywords, FIRST_X and
LAST_X have been added, so that you can select any section of an
image to ray trace. For example, you might wish to get the
lighting correct on a certain object; with the above keywords, you
can 'single out' that object, making for faster (preliminary)
traces, until you get the lighting correct.
Not noted in the accompanying (original) QRT documentation are the
following DEFAULT parameters: x_res, y_res, and aspect, which work
exactly as you'd expect them to.
QRT/ST OUTPUT FILES
QRT/ST outputs a non-format that I call 'RAW', for lack of a
better name. It has an extremely simple format, as follows:
"<xres> <yres>[lf]" The X and Y resolution of the file, as
ASCII strings seperated by a space, and
terminated with a linefeed (chr$(10)).
<r><g><b> One byte each of red, green, and blue for
each pixel. The bytes are in the range
of 0 to 255, proving a 24 bit colour
resolution (16 million colours).
The post-processor provided with QRT/ST, RAW2SPEC, uses advanced
dithering methods to reduce the 16 million colour output to 512
colours. For more information, read RAW2SPEC's documentation.
IMPORTANT NOTE
As of 03/08/91, I've not found an address of any sort for Steve
Koren, the author of QRT. If you know of any way to contact him,
let me know, because I'd like to notify him of this conversion.
As usual in this sort of thing, QRT/ST is yours to use at your own
discretion, and in the event of any accidental damages, neither I
nor Steve Koren may be held responsible.
QRT Ray Tracer Page 2 ST Reference
UNIMPORTANT NOTES
I chose QRT to port (as opposed to MTV or DKB) because I felt it
represented the best compromise of speed and features. You won't
be creating photorealistic images with QRT/ST (and if you could,
the ST certainly couldn't display them), but you can make some
incredible pictures, with a bit of time and effort.
I won't release the Laser C source for QRT/ST, so don't ask; not
only is it not mine to give, it has become unnecessarily cryptic
(partly Megamax, partly me). If you want the original Amiga
source, look on a few Amiga bulletin boards; that's where I found
it, at any rate.
If you create any images with QRT/ST and plan to upload them, you
might consider uploading the .QRT source as well, as there seems
to be a dearth of .QRT source in the public domain (those that I
included in the QRT/ST archive are all that I could find).
BUGS...
If you find any, please report them to me, rather than to Steve
Koren; they'll most likely be my fault, and if they're not, I'll
try to pass them on (if I ever find him).
I can be reached at the following:
Robert Barnhardt CompuServe: 73707,533
869 Garrison Road GEnie : R.BARNHARDT1
Fort Erie, Ontario
CANADA L2A 1N6
POST-SCRIPT
As of this writing, 04/08/91 02:00, I've just finished hardwiring
my floppy drive directly to my 520. At about 22:00 yesterday,
the drive ceased to respond to the constant cable-jiggling that
had previously kept it alive (if just barely).
If this setup goes on me, I'll have no way to call the on-line
services mentioned above; if you leave mail to me and I haven't
replied within a month, you can safely assume that I won't be
responding. At any rate, you can always reach me at the above
(real-world) address.
QRT Ray Tracer Page 3 ST Reference