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→Example: Tutorial Layer (TUT
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} | } | ||
} | } | ||
</syntaxhighlight> | |||
Next, we need to check tutorials.nas to see how it gets a list of targets for the corresponding tutorial, which can be seen below: | |||
<syntaxhighlight lang="nasal"> | |||
set_targets(tutorialN.getNode("targets")); | |||
</syntaxhighlight> | |||
So, basically, all we need to do is calling <code>tutorialN.getNode("targets");</code> to get a list of targets for the corresponding tutorial. | |||
Now, let's look up the definition of the set_targets() function, which is processing all targets, to see what we need to do to extract the latitude/longitude for each target: | |||
<syntaxhighlight lang="nasal"> | |||
## | |||
# For each <target><*><longitude-deg|latitude-deg> calculate and update | |||
# /sim/tutorials/targets/*/... | |||
# heading-deg ... absolute heading to target (0 -> North) | |||
# direction-deg ... relative angle to target (0 -> ahead, 90 -> to the right) | |||
# distance-m ... distance in meters | |||
# eta-min ... estimated time of arrival (assuming aircraft flies in | |||
# in current speed towards target) | |||
# | |||
var set_targets = func(node) { | |||
node != nil or return; | |||
var time = time_elapsedN.getValue(); | |||
var dest = props.globals.getNode("/sim/tutorials/targets", 1); | |||
var aircraft = geo.aircraft_position(); | |||
var hdg = headingN.getValue() + slipN.getValue(); | |||
foreach (var t; node.getChildren()) { | |||
var lon = t.getNode("longitude-deg"); | |||
var lat = t.getNode("latitude-deg"); | |||
if (lon == nil or lat == nil) | |||
die("target coords undefined"); | |||
var target = geo.Coord.new().set_latlon(lat.getValue(), lon.getValue()); | |||
var dist = aircraft.distance_to(target); | |||
var course = aircraft.course_to(target); | |||
var angle = geo.normdeg(course - hdg); | |||
if (angle >= 180) | |||
angle -= 360; | |||
var d = dest.getChild(t.getName(), t.getIndex(), 1); | |||
d.getNode("heading-deg", 1).setDoubleValue(course); | |||
d.getNode("direction-deg", 1).setDoubleValue(angle); | |||
var distN = d.getNode("distance-m", 1); | |||
var lastdist = distN.getValue(); | |||
distN.setDoubleValue(dist); | |||
if (lastdist != nil) { | |||
var speed = (lastdist - dist) / (time - last_step_time) + 0.00001; # m/s | |||
d.getNode("eta-min", 1).setDoubleValue(dist / (speed * 60)); | |||
} | |||
} | |||
last_step_time = time; | |||
} | |||
</syntaxhighlight> | </syntaxhighlight> | ||