* timo van Overbrüggen -- Monday 29 January 2007:
> I know, there is a "listener-command" but it do not work with
> properties in ".../jsbim/aero/.." so I can not link the
> listener-command to the aerodynamical forces.

listeners are triggered whenever something writes to the listened-to
property by means of SGPropertyNode methods (foo->setBoolValue() etc.)
But some properties are for performance reasons "tied". That is, the
tying C++ code can write to and read from the property value directly,
without using those methods. In that case listeners aren't triggered.

This is the case with jsbsim/aero/*. It wouldn't make much sense to
listen to those, anyway, as they probably change several times per
frame. I suggest to use a simple loop for your purpose, which should
in this case even be faster.



> My second problem is, that I only want to show the force-or the
> momentarrows. Is there somebody who can explain me how to do that? 

I had once planned to do that myself. Just make an extra 3D model
with the arrows and load that to your aircraft model in your main
*.xml animation file. You can add a <condition> to turn the whole
submodel on and off.

  <model>
      <path>moment_arrows.xml</path>
      <condition>
          <property>/path/to/switch</property>
      </condition>
  </model>

In the moment_arrows.xml file you define animations to rotate the
arrows. Their length can be controlled with scale animations along
one axis. I almost want to write the code myself now ...  :-)

m.

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