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Using listeners and signals with Nasal: Difference between revisions
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Using listeners and signals with Nasal (view source)
Revision as of 19:50, 19 May 2013
, 19 May 2013→Nasal code coupled to the autopilot system: http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg13025.html
(→Nasal code coupled to the autopilot system: http://flightgear.org/forums/viewtopic.php?f=46&t=17069&hilit=nasal+fdm+autopilot&start=15#p165551) |
m (→Nasal code coupled to the autopilot system: http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg13025.html) |
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=== Nasal code coupled to the autopilot system === | === Nasal code coupled to the autopilot system === | ||
The FDM doesn't run at a fixed rate, either. It runs 120 times per second (if so configured), but it runs all iterations for a frame one after the other, then waits until the next frame. | |||
Some people have a need to run Nasal code at the same rate as the simulation. Currently, without modifying the source code for FlightGear, the only way | Some people have a need to run Nasal code at the same rate as the simulation. Currently, without modifying the source code for FlightGear, the only way | ||
to do this is to find a property updated at the right time in the simulation cycle and set a listener on it. From a code quality standpoint, this is less than ideal. | to do this is to find a property updated at the right time in the simulation cycle and set a listener on it. From a code quality standpoint, this is less than ideal. | ||
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</syntaxhighlight> | </syntaxhighlight> | ||
Some core developers are fairly opposed to the whole idea, i.e. want to avoid *any* Nasal in the fast simulation loop of the FDM, because Nasal execution is slow and non-deterministic because of its GC issue. Running it in the fast simulation loop is the last thing they want[http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg38172.html]. | |||
You can then use Nasal for the high level stuff, and enable/disable/switch the individual controller elements (e.g. in order to automatically switch the autopilot mode when capturing the ILS). There are some nice examples with fgdata/Git aircraft. You could look at the 777. | You can then use Nasal for the high level stuff, and enable/disable/switch the individual controller elements (e.g. in order to automatically switch the autopilot mode when capturing the ILS). There are some nice examples with fgdata/Git aircraft. You could look at the 777. | ||
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Some benefits to such an approach include (IMHO) better testability, more predictability, and easier interface (someday) with a GUI tool, should one | Some benefits to such an approach include (IMHO) better testability, more predictability, and easier interface (someday) with a GUI tool, should one | ||
materialize. The downside is that XML can be verbose. | materialize. The downside is that XML can be verbose. | ||
All that being said, it is definitely possible to run Nasal in the FDM update loop, so to make up your own mind, you could try this: | All that being said, it is definitely possible to run Nasal in the FDM update loop, so to make up your own mind, you could try this: | ||