Mops-FAQ.txt [27. Feb 2000]

This document tries to answer some commonly asked questions
regarding The Mops.

There is not much here, feel free to send mail to improve
this situation.

The latest version of this document can be found at:
http://www.informatik.uni-rostock.de/~rschultz/mops/Mops-FAQ.txt

Content/Questions:

0) I found a bug! What should I do?

Section 1 - Questions regarding compiling, installation and setup
-----------------------------------------------------------------
1.1) The hotkey Ctrl+T (Shift-Tab etc.pp.) does not work.
1.2) The Mops does not start, because of a missing libGLU or libGL, but
     I do have Mesa installed.
1.3) The Mops seems to start correctly, but all I get is an empty
     window and a strange "%" symbol in the shell.
1.4) The Mops crashes on startup but I have been able to read
     something of a "Tip of the day".
1.5) The Mops crashes when opening a second view, or when reading
     a scene with more than one view.
1.6) The Main window of The Mops jumps, when it automatically resizes
     to the property GUIs. What can I do about this?

Section 2 - "How do I"-questions
--------------------------------

2.1) How do I set up the reflectivity or refraction of an object?
2.2) How do I control the camera, setting exact from and to values?
2.3) How do I import data from my application to The Mops, do you
     publish The Mops file format?
2.4) How do I create a standard 3 or 4 view working environment,
     that is usable over more than one session?

-----------------------------------------------------------------
-----------------------------------------------------------------

Answers:

0) I found a bug! What should I do?

Before sending mail, check out the appropriate section
of The Mops Home Page to see if the bug is already known:
http://www.informatik.uni-rostock.de/~rschultz/mops/bugs.html

If it is not, please send mail containing at least the
following information:
- Mops version (see Help/About)
- your operating system
- what OpenGL and which version of BMRT are you using
- how to reproduce the error
  (do not send mails about non reproducible things!)
- a small example scene (if it is helpful).


Section 1 - Questions regarding compiling, installation and setup
-----------------------------------------------------------------


1.1) The hotkey Ctrl+T (Shift-Tab etc.pp.) does not work:

Take a look at the output of "xev" to check whether your X is configured to
send the right events. On some systems Shift+Tab generates
"ISO_Left_Tab" instead of "Tab". You can change that e.g.
using xmodmap by adding the line
keysym ISO_Left_Tab = Tab
to your ~/.Xmodmap (which you use in your .xinitrc this way:
xmodmap ~/.Xmodmap)

Alternatively, you can change the appropriate entries in your mopsrc
to customize the keyboard shortcuts.


1.2) The Mops does not start, because of a missing libGLU or libGL, but
     I do have Mesa installed.

Mesa, being just an implementation of OpenGL, is often installed
as libMesaGL.so, which surely will not be found by an application
which needs OpenGL, but not specifically Mesa, and therefore
has been linked with libGL.so.
The solution is to improve your crude Mesa installation by
establishing softlinks named libGL.so that point to your installed
libMesaGL.so.
Installing Mesa3.1 will also solve this problem, as from V3.1 on
Mesa installs as libGL.so.


1.3) The Mops seems to start correctly, but all I get is an empty
     window and a strange "%" symbol in the shell.

You built a shared version of The Mops which acts like
a wish (the Tcl/Tk shell) when started without arguments.
A "make install" would have created a shell script for you,
that calls the binary "mopssh" with the right argument,
but you can also start The Mops by hand:
> ./mopssh mopstcl.tcl


1.4) The Mops crashes on startup but I have been able to read
     something of a "Tip of the day".

The Mops were about to open a first view window, and crashed.
Several problems may lead to this:
- You did not compile Togl correctly; please go back to the Togl
  distribution, and try to compile a Togl example first, get that
  to run, then try The Mops again. Do not forget to recompile The
  Mops with the new togl.o!
- The Mops did not find an appropriate visual; make sure that you
  have OpenGL installed and that it really works;
  running The Mops on low-color-displays (e.g. 16 colors) may also lead
  to this behaviour, do not do this!


1.5) The Mops crashes when opening a second view, or when reading
     a scene with more than one view.

This might be a problem with GLX, which you may work around by
setting the environment variable DISPLAY to "localhostname:0.0".
(It did work for me on a NetBSD system, using the standard Mops
binary in the Linux emulation with Mesa3.1.)


1.6) The Main window of The Mops jumps, when it automatically resizes
     to the property GUIs. What can I do about this?

From V0.42d on, The Mops knows a preference setting named
"twmcompat" that controls a work-around for the different
behaviour of some window managers (like e.g. twm).
If you suffer from "jumping" windows, go to the mops console,
type:
> set prefs(twmcompat) 1
then save preferences.


Section 2 - "How do I"-questions
--------------------------------

2.1) How do I set up the reflectivity or refraction of an object?

There are no such attributes in the RenderMan standard,
thats why you do not find e.g. reflectivity in the attribute property.
You may set the reflectivity of a surface by applying the
right surface shader to the object (for instance "shiny"),
then use the right parameter of that shader (Kr is the reflectivity
parameter of the "shiny" shader).


2.2) How do I control the camera, setting exact from and to values?

Simply go to the top level of your scene, double-click on the
Scene object, and select the view you want to change. Then edit
its "Camera" property. 


2.3) How do I import data from my application to The Mops, do you
     publish The Mops file format?

No, and I do not intend to do so.

Your options are:
a) write your data in another format The Mops understands,
   this is e.g. 3DMF. I know, that you currently cannot import
   3DMF under Win32 but this will change with the next release.
b) write an import plugin for your data, if it is in a commonly
   used format more people could perhaps profit from that.
   Take a look at the mfio.c file, it should give you an idea
   about how easy it is to write such a thing.

2.4) How do I create a standard 3 or 4 view working environment,
     that is usable over more than one session?

This is simple:
o Start The Mops.
o Create and adjust your 3 or 4 views.
o Save the scene to a file "my3views.mop"
o Quit The Mops.
o Load the scene on next startup using the filename of your
  scene as argument to the Mops executable.

Remember that you now have to take care about the preference setting
"SaveViews" when saving scenes, because the 3 or 4 views get saved into
every scene by default!

# EOFAQ
