Dear QRT user(s), Once upon a time, when there were only a few people interested in QRT, I used to write individual replies to anyone from whom I received a letter. I also sent the complete QRT source on disk to anyone who was missing various pieces. This worked fine until recently, when there has been a large increase in the number of people interested in the system. I am currently receiving 1 or 2 letters a day. At first I tried to respond to all these with a "custom" letter, but I ended up spending 2 hours each evening typing and printing letters. Also I've probably spend around $75 to send disks to various people. Since QRT is not a commercial product, nor is it even shareware, I can afford neither the time or money necessary to continue the individual replies. Hence this "form" letter. I hope this does not insult anyone - while I really do enjoy hearing from people who are using QRT, I just do not have the time to reply to everyone individually. There are a number of questions and comments that I hear often enough that I will try to address them here, in hopes this will answer a large percentage of the questions asked. If there are any other questions, I will try to append a short note to this letter to address these. So here we go: the List of 13 Most Frequently Asked QRT Questions: ---------------------------------------------- 1) Q. "I do not have source to QRT, but I have read in the docs that it should be provided. Where is it?" A. I do not distribute QRT myself to all the BBS systems it is on. Instead I upload it to the Cleveland Area Amiga Users Group BBS, and it propegates around in a very uncontrolled manner, as various people copy it to other places. If someone in this chain decides to omit, say, the source code, I cannot change the fact that all copies made from this person or BBS will have the source code ommitted. The full and complete system, (currently in release 1.4), is available from the aforementioned BBS, at (216)-581-2284. I have also given 1.4 to Fred Fish, in hopes he will include it in his PD Amiga library. The files are: QRTSRC14.ARC (source code) QRT14.ARC (executables) QRTDOC4A.ARC (documents) QRTINP.ARC (small collection of QRT input file) (demos): TABLE.ARC (a nice demo of a glass table) MIRROR.ARC (sample of various mirror characteristics) WALLSPH.ARC (sample of pattern mapping to spheres) PIANO.ARC (sample of complex patterns) These demos are much nicer than the ones included with the original 1.1 release of QRT. You might want to check them out. 2) Q. "I don't have the user manual for QRT, even though I have the other manuals." A. Ok, this one is my fault. When I put 1.4 on the BBS system in Cleveland, I accidentally left out the user manual. I quickly noticed my mistake, and put the correct version out (QRTDOC4A.ARC), but it seems that the bad version has been copied to a near endless number of places. I can't possibly hunt them all down, so I'm depending on the people who copied the bad manuals to just use the version from QRT 1.3, if you have that. If not, you can perhaps get it from the above BBS. 3) Q. "I type QRT, and nothing happens." A. There could be a few possible causes. First, ray tracers, even fast ones, take a long time to generate an image. You have to wait, anywhere from 15 minutes to 8 hours depending on the image. Also, alot of people forget to re-direct standard input. You MUST do this. If you type "RUN QRT IMAGE.QRT", it WILL NOT WORK. The correct form is "RUN QRT IMAGE.OUT". The RUN command runs QRT in the background (use an & to do this on UNIX). 4) Q. "I don't have enough memory to run QRT." A. Sorry. Buy more memory - its very useful for alot of things besides QRT. I recommend at least 1 megabyte, or more if you commonly run alot of things all at once. 5) Q. "My drive runs off an on for an hour." A. QRT is writing the image file as it generates it. I recommend saving the file to either a ram disk, if you have enough memory, or a hard drive. The hard drive will NOT be run continuously, since QRT spends most of its time thinking and very little actually writing to the disk. 6) Q. "Triangles don't seem to work properly." A. Indeed, they do not work properly. This is a bug (sorry!). They tend to work for right triangles, but no others. I have stopped all work on the code due to time constraints, but if anyone wants to fix this bug, it will be simple. The problem is in the line/triangle intersection routine in INTERSECT.C. Fix that, and your problem will go away. Also, you can simulate a triangle by using a parallelogram and the REMOVE command. This should work OK. 7) Q. "I am having troubles with glass objects." A. Yeah, I know, there are alot of parameters to be fiddled with to get nice looking glass. First of all, if you have version 1.3 or earlier, glass won't work at all. Version 1.4 fixes this problem (see the TABLE.QRT and TABLE.ILBM files for a nice example of glass objects). QRT will also correctly handle hollow glass objects; I may yet release a sample file for this. The only thing I can say is that you should understand what the different parameters do, and be prepared to play around with the image. Its complex, but it works. 8) Q. "I can't map patterns to quadratic surfaces." A. Another bug. Patterns will, however, map correctly to the other object types (see the files PIANO.QRT and PIANO.ILBM for an example of some complicated pattern definitions). 9) Q. "I'd like to be able to simulate wood/marble/etc surfaces." A. This is not all that easy, but it IS possible. The PIANO files mentioned above have a reasonable wood grain definition. Someday I may add support for mapping IFF pictures to objects, but this will remove the machine independence from QRT. Another approach is to add wood, marble, etc as hardcoded QRT surfaces. This would be very easy given the current QRT architecture. Just add a function that takes in x and y positions and returns the appropriate COLORINFO structure. 10) Q. "Do QRT post processors exist for other machines besides the Amiga?" A. Yep. I haven't written any of them, however, as I only have an Amiga. You're on your own to find them. Here are some machines that post processors are supposed to exist for: Amiga (of course) Amiga + 68020 + 68881 (rumor only - somebody recompiled to + 68030 + 68882 make optimal use of the fancy hardware) IBM/HP Vectra (needs a 386 or 286 with math co-processor. Also, these machines have no multitasking, so the machine will be unusable while QRT runs. You'll need *at least* 64 simultanious colors - 256 is really much better. 16 doesn't cut it.) HP 800 series (825, 835, 850, etc - these are FAST high end graphics workstations - somebody is supposed to be developing a post processor for them - we're talking 1280x1024 in 24 bit planes here) Mac II (heard rumors, but nothing concrete. Same comment about lack of multitasking applies here). 11) Q. "I've heard there is a QRT 2.0. Where can I get it?" A. Beats me. I've heard of a version 2.0, but I certainly didn't write it, so apparently somebody else has done something else with it. If it is a simple re-compile using 68881 libraries, I'd say it only warrents a 1.4fp, but if somebody developed, say, an interactive 3d graphics editor or something, this is significant. If anybody knows anything about this, I'd certainly like to know. 12) Q. "Is there a QRT mailing list or user's group?" A. I can't promise that I'll keep a mailing list of QRT users. If QRT was a shareware or commercial product, I certainly would, but since its free, I can't devote the resources to it. Also, I don't think there is a user's group. I do, however, upload all new versions to the Cleveland Area Amiga User's Group BBS, and message can be left there for me. 13) Q. "What features will I see in future versions of QRT?" A. I can't even promise there will BE any future versions after 1.4. First of all, I am sick of doing software development on a floppy based system, so until I get an A2000 with a hard drive, I probably won't touch the source. Second, I have less time than I used to. Third, there are other things I'd like to work on. Any future version will probably be mostly bug fixes and small upgrades; I don't have anything major planned. Ok, that should answer about 90% or so of the questions asked. If there are others, I will try to answer them individually on a case by case basis. Sincerely, Steve Koren 4501 Boardwalk Dr. Apt D-38 Fort Collins, CO 80525 USA