home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Atari Mega Archive 1
/
Atari Mega Archive - Volume 1.iso
/
graphics
/
qrt.lzh
/
LETTER.TXT
< prev
next >
Wrap
Text File
|
1989-02-18
|
10KB
|
216 lines
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.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