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: " [lf]" The X and Y resolution of the file, as ASCII strings seperated by a space, and terminated with a linefeed (chr$(10)). 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