Q: With respect to some special details the behaviour of
SCHAKAL seems to be rather weird. Do you agree?
A: No doubt about it. Actually, you either might have found a new bug (hitherto
unknown to me) or you just encountered another example of unskilled, suboptimal
programming. Please
e-mail me in such a case. Also have a look at the other FAQ sections,
below.
Q:
The generation of H bonds by {cryst / bld+h} and {cryst / bld+hp} works correctly in many cases,
but sometimes wrong H bonds are generated; in other cases, some
H bonds are missing. What about this?
A: Several bugs in the H-bonds-finding routines have been removed from the
program over the last 5 years.
I wouldn't bet my life though that these routines are absolutely
free-of-bugs, by now, as H-bonds don't belong to our daily business.
(NEW)
Note that the detection of a H bond requires that the H atom in question
is positioned at a more or less reasonable position: a H bond is generated
only when the H---Donor distance is of suitable length. Length ranges for
the different donors can be adjusted in the file addhb.scf (each range
has to be modified several times).
C-H---Donor bridges are not generated by the program.
Q: (NEW)
How can I stop drawing once it has started?
A: By pressing the <ESC> key on the keyboard. Any time, the string "<ESC>"
appears in the 4th row of the GUI, the current action can be terminated by
pressing this key. If only "ESC" appears, the current action can also be
terminated by clicking the {ESC} button with the mouse.
Q: It's practically impossible to remember the meanings of all these
cryptically labeled control fields of the GUI. Any advice ?
A: The meaning of a control field (or an individually coloured part
of a control field) is - in most cases - briefly explained if you
click it with the right mouse button.
Q: How can I get rid of these parameter and colour boxes in the
2nd and 3d rows of the GUI once I don't need them any more ?
A: click on one of the two grey buttons just to the left of the large OK button
(the one on the left side).
Q: Why don't these things disappear automatically when clicking
the OK button ?
A: The advantage is that the command in question remains
"latently active". Suppose that you have made a shaded drawing by
clicking the yellow part of { shade }. As the drawing seems to be
too dark, you set a darkness parameter of 0.8
by means of the 'MDF darkness' parameter box.
After the image has been re-drawn (by clicking the red star in { USE }),
you feel that 0.9 would have been a better choice. You now may just
increase the value of 0.8 in the parameter box to 0.9 , click { OK },
and start the next drawing by clicking the red star in { USE }.
And so on, without having to re-generate the 'MDF Darkness'
box after each drawing.
Q: (NEW)
In the on-screen rotations box the default (wire) model undergoes simple rotations.
If I select a { Q } or { L } etc. drawing, however, the position of the rotation axis
and the size of the model apparently are continuously re-adjusted (i.e., the rotation doesnt
look "naturally"). Is this avoidable ?
A: Yes, just fix the scale factor by clicking somewhere at the unit (consisting of the
control bar and the two control buttons) to the right of the word "scale".
Q: TIFF Images taken from the screen are of poor quality when printed
in a medium or large format. This is especially true if pellucidity effects
have been used. What to do?
A: Try a larger resolution via the { resxn } procedure (2 or 3 times the
screen resolution should do it in most cases). I get best results when I first
read such a file with enhanced resolution into an image processor
(Micrografx' Picture Publisher). I then convert the file into an
RGB file, sometimes apply a weak blurring effect, cut the image (if necessary),
reduce its size "smoothly" to the desired one
(e.g. 20 cm width), then change to the desired printer resolution (e.g. 300 dpi).
Finally, in most cases, I use the "selective sharpening" effect of the image
processor. This gives images of very good quality on my 300 dpi HP 890C
colour printer (a very similar procedure is possible with Corel's Photopaint image
processor).
Q: When viewing SCHAKAL's TIFF files with some other software,
the images look o.k., some times, but some other times, I get
these strange grid-like patterns. Any comments?
A: This can happen if the image has been drawn using pellucidity effects
or regular dithering (some distributed command files use these effects). As these
effects base on periodic alterations in the pixel values, Moire-like patterns
may occur when the image is displayed with a pixel resolution (X x Y) which
differs from the image's original resolution. To overcome this, you may
modify the image file using a procedure similar to the one described in the previous answer.
Q: Can I convert a printer drawing into a TIFF/.pcx image?
A: Not with SCHAKAL.
Q: Can SCHAKAL read TIFF or .pcx files from other sources ?.
A: No. The same is valid for HPGL, EPS or WMF files.
Q: TIFF/.pcx images, when restored or printed, show atoms
with ugly white spots. What to do?
A: This happened on some Win32 systems with older program versions.
Use the command 'G D ! 3'. If this helps, you can insert the command into the file
sch99.ini (using a text editor). The versions released after April 2001 are
supposed to be free of this problem.
Q: (NEW)
We use .EPS and/or .WMF files to generate line style drawings. However, the lines
in these drawings are rather broad. How can we get thinner lines?
A: This can be achieved by means of the 'Set Resolution ...' command.
With the 1st parameter the lines in .EPS files can be controlled, the 1st and 2nd parameters
affect line widths in .WMF files. Examples:
| S R .012 | (for .EPS files; default parameter is .025) | |
| S R .011 4 | (for .WMF file; default parameters are 0.025 and 10) |
Note that the reduction of the resolution parameters will blow up the drawing times and file sizes especially for smoothly shaded drawings!
Once suitable resolution parameters have been found (say, the values given above) they could be made permanent by inserting the commands 'G D ! 603 .012' (EPS) or 'G D ! 703 .011 4' (WMF) into the file sch99.ini .
Q: Why do the scroll bars in the built-in editor work incorrectly ?
A: This is a bug in the Salford compiler system which is the link
between SCHAKAL's FORTRAN source code and Windows.
Q:
Which is the best way to make printouts on a LaserJet 3-6 or a
fully compatible printer?
A: Don't use the Windows Printer (Device no. 8) in this case, but use
device no. 4 . Per default, this device (like devices 3,5, and 6)
assumes, that the printer is
connected to your computer by the LPT1: interface. If it is another
interface, or if the LaserJet is accessible via the net, use the
command 'U P -104 "xxxxxx" '
to redirect the printer output. Example:
U P -104 "\\server2\printer1"
Once this is working you might insert the command into the file sch99.ini.