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Implementation Specific Questions
X Windows Specific Questions
See the discussion of rendering options in the next question.
These control allow you to change how the X11 version renders
objects. The dithering checkbox, which only appears when running
on an eight bit display, allows you to turn dithering on and off.
Dithering is the method by which Geomview uses a small set of
colors (less than 217) to show any color you request. This is
done by placing pixels of slightly different color next to each
other and letting your eye blend them together. Unfortunately,
it takes a fair bit of computing to do this. Turning it
dithering off will speed up rendering, but colors used won't be
exactly what you want. Depending upon your scene, this may be an
acceptable tradeoff.
The Z-Buffer popup menu allows you to select between three different
methods of hidden line/surface removal: z-buffering, depth sort,
and none. Z-buffering is the most accurate and enables the near
and far clipping planes. Depth sort uses less computing, but
will be inaccurate if objects intersect (polygons will pop in
front when they should be partially obscured) and in certain
other circumstances (long, narrow polygons close to other
polygons are one example). Depending on your scene, using this
method could look just the same as z-buffering but be much
faster. The "None" option turns off all hidden line/surface
removal. This is only recommended for a scene which consists of
just lines in one color.
This happens when using the X11 version on an eight bit
display (currently common on workstations). An eight
bit display can only show 256 colors simultaneously. These
colors are shared by all the programs running. Once a
colorcell has been allocated by an application, its color is
fixed. Geomview tries to grab many colors when it starts.
If it fails to get them, it prints this message and uses a
private colormap. A private colormap means that Geomview now has
access to all 256 colorcells. Unfortunately, these colors will
only be displayed when the cursor is inside one of Geomview's
windows. The switching of colormaps when the cursor enters and
leaves the windows will give a technicolor look to the rest of
the display.
If you don't like the technicolor effect, you will have to quit
the programs which are using up colormap space. Examples of
programs which use lots of colormap space are background
pictures, image viewers, visualization software, and WWW browsers.
The X11 version of Geomview uses the shared memory extension to
move images quickly between the program and the X server.
However, this method of communicating with the X server only
works when running Geomview on the same machine as the display.
If Geomview can't use shared memory, it prints this message and
goes back to using standard X calls. Everything will work the
same, it will just run much slower, especially if you're running
over the network.
The current release of Geomview (1.5.0) doesn't accept any
standard X command line options. This will be fixed for the next
release. In the meantime, you can accomplish the same thing by
typing setenv DISPLAY whatever:0 in [t]csh or
DISPLAY=whatever:0 ; export DISPLAY in sh.
You're trying to compile the X11 version and the compiler can't
find the Motif header files. If you have Motif but the headers
are in a nonstandard place, change the "SYSCOPTS" in your
makefiles/mk.${MACHTYPE} file. If you don't have Motif, you
won't be able to compile Geomview. In this case, use one of the
binary distributions, if you can.
Yes, Geomview can be built to use the Motif interface on the SGI.
We don't distribute binaries for this, so you'll have to compile
it yourself. There are comments in makefiles/mk.sgi showing
how to build this version. This configuration of Geomview is not
fully tested, so you may run into problems.
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Created: Fri Sep 8 11:39:00 1995 ---
Last modified: Mon Sep 25 12:02:10 1995