20,741
edits
Using listeners and signals with Nasal: Difference between revisions
Jump to navigation
Jump to search
m
Using listeners and signals with Nasal (view source)
Revision as of 19:56, 19 May 2013
, 19 May 2013→Nasal code coupled to the autopilot system
m (→Nasal code coupled to the autopilot system: https://code.google.com/p/flightgear-bugs/issues/detail?id=421#c13) |
|||
| Line 217: | Line 217: | ||
There's just one (minor) problem at the moment. There's no generic FDM update() function where one could put a sig.setDoubleValue(dt).This would have to be done in all FDMs. | There's just one (minor) problem at the moment. There's no generic FDM update() function where one could put a sig.setDoubleValue(dt).This would have to be done in all FDMs. | ||
There are several options, such as 1) Run a second events system and add an additional parameter to Nasal's settimer allowing you to use this new events system. 2) Add in a signal that is fired each simulation step, probably right before the Autopilot system is run: | Another possibility is to extend the declarative expression logic, which is already supported by the autopilot components, to allow a Nasal expression. Then you mix the declarative components (which you're going to want for most autopilot laws) with some scripted ones. | ||
Since the expression evaluation would be driven by the autopilot subsystem, it would run at whatever frame-rate that itself runs at - which is currently in lock-step with the FDM [http://flightgear.org/forums/viewtopic.php?f=46&t=17069&hilit=nasal+fdm+autopilot&start=15#p165596]. | |||
There are several other options, such as 1) Run a second events system and add an additional parameter to Nasal's settimer allowing you to use this new events system. 2) Add in a signal that is fired each simulation step, probably right before the Autopilot system is run: | |||
<syntaxhighlight lang="php"> | <syntaxhighlight lang="php"> | ||
| Line 238: | Line 241: | ||
is the way that JSBSim has approached the solution. | is the way that JSBSim has approached the solution. | ||
Some benefits to such an approach include | Some benefits to such an approach include 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: | ||