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fgdata/Nasal/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
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;
}
# For each runway complement the opposite end, as airportinfo() returns only one end.
#
var complement_runways = func(apt) {
foreach (var rwy; keys(apt.runways)) {
if (!string.isdigit(rwy[0]))
continue;
var number = math.mod(num(substr(rwy, 0, 2)) + 18, 36);
var side = substr(rwy, 2, 1);
var comp = sprintf("%02d%s", number, side == "R" ? "L" : side == "L" ? "R" : side);
var r = apt.runways[rwy];
apt.runways[comp] = { lat: r.lat, lon: r.lon, length: r.length,
width: r.width, heading: math.mod(r.heading + 180, 360),
threshold1: r.threshold2,
#threshold2: r.threshold1
#stopway1: r.stopway2, stopway2: r.stopway1,
};
}
}
# 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 + 180, rwy.length / 2 - rwy.threshold1 - 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[0] != `H`)
is_heliport = 0;
if (is_heliport) {
#print(apt.id, " -- \"", apt.name, "\" --> heliport; ignored");
} else {
complement_runways(apt);
draw_tunnel(best_runway(apt));
#print(apt.id, " -- \"", apt.name, "\"");
}
}
settimer(func { loop(id) }, INTERVAL);
}
var loopid = 0;
settimer(func {
var top = props.globals.getNode("/sim/model/geometry/square/top", 1);
if (top.getType() == "NONE")
top.setBoolValue(1); # remove top bar unless otherwise specified
setlistener("/sim/rendering/glide-slope-tunnel", func(n) {
loopid += 1;
if (n.getValue()) {
apt = nil;
loop(loopid);
} else {
forindex (var i; tunnel) {
if (tunnel[i] != nil) {
tunnel[i].remove();
tunnel[i] = nil;
}
}
}
}, 1);
}, 0);