Source glide_slope_tunnel.nas
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# Draw 3 degree glide slope tunnel for the nearest airport's most suitable runway
# considering wind direction and runway size.
# Activate with --prop:sim/rendering/glide-slope-tunnel=1 or via Help menu
var MARKER = "Models/Geometry/square.xml"; # tunnel marker
var DIST = 1000; # distance between markers
var NUM = 30; # number of tunnel markers
var ANGLE = 3 * math.pi / 180; # glide slope angle in radian
var HOFFSET = 274; # distance between begin of runway and touchdown area (900 ft)
var INTERVAL = 5; # check for nearest airport
var voffset = DIST * math.sin(ANGLE) / math.cos(ANGLE);
var apt = nil;
var tunnel = [];
setsize(tunnel, NUM);
var normdeg = func(a) {
while (a >= 180)
a -= 360;
while (a < -180)
a += 360;
return a;
}
# Find best runway for current wind direction (or 270), also considering length and width.
#
var best_runway = func(apt) {
var wind_speed = getprop("/environment/wind-speed-kt");
var wind_from = wind_speed ? getprop("/environment/wind-from-heading-deg") : 270;
var max = -1;
var rwy = nil;
foreach (var r; keys(apt.runways)) {
var curr = apt.runways[r];
var deviation = math.abs(normdeg(wind_from - curr.heading)) + 1e-20;
var v = (0.01 * curr.length + 0.01 * curr.width) / deviation;
if (v > max) {
max = v;
rwy = curr;
}
}
return rwy;
}
# Draw 3 degree glide slope tunnel.
#
var draw_tunnel = func(rwy) {
var m = geo.Coord.new().set_latlon(rwy.lat, rwy.lon);
m.apply_course_distance(rwy.heading, rwy.threshold + HOFFSET);
var g = geodinfo(m.lat(), m.lon());
var elev = g != nil ? g[0] : apt.elevation;
forindex (var i; tunnel) {
if (tunnel[i] != nil)
tunnel[i].remove();
m.set_alt(elev);
tunnel[i] = geo.put_model(MARKER, m, rwy.heading);
m.apply_course_distance(rwy.heading + 180, DIST);
elev += voffset;
}
}
var loop = func(id) {
id == loopid or return;
var a = airportinfo();
if (apt == nil or apt.id != a.id) {
apt = a;
var is_heliport = 1;
foreach (var rwy; keys(apt.runways))
if (rwy and rwy[0] != `H`)
is_heliport = 0;
if (!is_heliport) {
draw_tunnel(best_runway(apt));
gui.popupTip(apt.id ~ " - \"" ~ apt.name ~ "\"", 6);
}
}
settimer(func loop(id), INTERVAL);
}
var loopid = 0;
var fdm_init_listener = _setlistener("/sim/signals/fdm-initialized", func {
removelistener(fdm_init_listener); # uninstall, so we're only called once
# remove top bar unless otherwise specified
var top = props.globals.initNode("/sim/model/geometry/square/top", 1, "BOOL");
setlistener("/sim/rendering/glide-slope-tunnel", func(n) {
loopid += 1;
if (n.getValue()) {
apt = nil;
return loop(loopid);
}
forindex (var i; tunnel) {
if (tunnel[i] != nil) {
tunnel[i].remove();
tunnel[i] = nil;
}
}
}, 1);
});