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Tyre effects (spray, smoke) rework

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Spray density realism improved by using a curve for the density and permitting the trigger to be changed (default 0.2)

Touchdown smoke trigerred by WoW changing using the velocity as a factor and then using a low pass filter on this to fade out the smoke. This results in smoke for a brief period that appears to be more realistic. F-14 example: https://i.imgur.com/FkwgoYV.gifv
This commit is contained in:
Richard Harrison 2021-10-18 15:27:23 +02:00
parent 9549655c2e
commit dc697141b8
1 changed files with 99 additions and 30 deletions
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129
Nasal/aircraft.nas
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@ -811,35 +811,40 @@ var autotrim = {
# Note: in reality, tyre smoke doesn't depend on vspeed, but only on acceleration
# and friction.
#
# rain_norm_trigger: threshold for deciding that there is enough standing water to
# calculate spray. This is compared against rain-norm.
#
var tyresmoke = {
new: func(number, auto = 0, diff_norm = 0.05, check_vspeed=1) {
new: func(number, auto = 0, diff_norm = 0.05, check_vspeed=1, rain_norm_trigger=0.2) {
var m = { parents: [tyresmoke] };
m.vertical_speed = (!check_vspeed) ? nil : props.globals.initNode("velocities/vertical-speed-fps");
m.diff_norm = diff_norm;
m.speed = props.globals.initNode("velocities/groundspeed-kt");
m.rain = props.globals.initNode("environment/metar/rain-norm");
m.rain_node = props.globals.initNode("environment/metar/rain-norm");
m.rain_norm_trigger = rain_norm_trigger;
var gear = props.globals.getNode("gear/gear[" ~ number ~ "]/");
m.wow = gear.initNode("wow");
m.wow_node = gear.initNode("wow");
m.last_wow = m.wow_node.getValue();
m.tyresmoke = gear.initNode("tyre-smoke", 0, "BOOL");
m.friction_factor = gear.initNode("ground-friction-factor", 1);
m.friction_factor_node = gear.initNode("ground-friction-factor", 1);
m.sprayspeed = gear.initNode("sprayspeed-ms");
m.spray = gear.initNode("spray", 0, "BOOL");
m.spraydensity = gear.initNode("spray-density", 0, "DOUBLE");
m.auto = auto;
m.listener = nil;
me.lastwow=0;
if (getprop("sim/flight-model") == "jsb") {
var wheel_speed = "fdm/jsbsim/gear/unit[" ~ number ~ "]/wheel-speed-fps";
m.rollspeed = props.globals.initNode(wheel_speed);
m.get_rollspeed = func m.rollspeed.getValue() * 0.3043;
m.rollspeed_node = props.globals.initNode(wheel_speed);
m.get_rollspeed = func m.rollspeed_node.getValue() * 0.3043;
} else {
m.rollspeed = gear.initNode("rollspeed-ms");
m.get_rollspeed = func m.rollspeed.getValue();
m.rollspeed_node = gear.initNode("rollspeed-ms");
m.get_rollspeed = func m.rollspeed_node.getValue();
}
m.lp = lowpass.new(2);
m.lpf_touchdown = lowpass.new(0.15);
auto and m.update();
return m;
},
@ -850,30 +855,93 @@ var tyresmoke = {
}
me.auto = 0;
},
update: func {
var rollspeed = me.get_rollspeed();
var vert_speed = (me.vertical_speed) != nil ? me.vertical_speed.getValue() : -999;
var groundspeed = me.speed.getValue();
var friction_factor = me.friction_factor.getValue();
var wow = me.wow.getValue();
var rain = me.rain.getValue();
calc_spray_factor: func(groundspeed_kts)
{
# based on Figure 31(a)[1]; Variation of drag parameter with ground speed in water
# for dual tandem wheels without spray-drag alleviator curve fitted and normalized.
#
# My The logic here is that the spray will be a factor of the drag and using the
# curve from Figure 31(a) is at least based in reality, whereas previously
# a simple factor was used which tended to give spray at much too low groundspeeds.
#
# |
# |
# 1 | +-------------------------------------------------
# | __/
# | /
# | /
# | /
# | /
# | /
# | /
# | /
# | /
# | /
# | /
# | /
# | /
# | /
# | _/
# 0| __--
# +--------------------------------------------------------------------
# 0 20 40 60 80 100 120 140 160 180 200 220 240
#
#_______________________________________________________________________________
# ref: https://ntrs.nasa.gov/api/citations/19660021919/downloads/19660021919.pdf
#-------------------
# Curve fit: MMF Model: y = (a * b + c * x ^ d) / (b + x ^ d)
# Coefficient Data: a=0.03048 b=59175231 c=2.38119 d=5.08271
# Normalized by using max value 2.38105217250475
var filtered_rollspeed = me.lp.filter(rollspeed);
var diff = math.abs(rollspeed - filtered_rollspeed);
var diff_norm = diff > 0 ? diff / rollspeed : 0;
return ((0.03048 * 59175231 + 2.38119 * math.pow(groundspeed_kts, 5.08271))
/ (59175231 + math.pow(groundspeed_kts, 5.08271)) / 2.38105217250475)
;
},
update: func {
me.rollspeed = me.get_rollspeed();
me.vert_speed = (me.vertical_speed) != nil ? me.vertical_speed.getValue() : -999;
me.groundspeed_kts = me.speed.getValue();
me.friction_factor = me.friction_factor_node.getValue();
me.wow = me.wow_node.getValue();
me.rain = me.rain_node.getValue();
if (wow and vert_speed < -1.2
and diff_norm > me.diff_norm
and friction_factor > 0.7 and groundspeed > 50
and rain < 0.20) {
me.filtered_rollspeed = me.lp.filter(me.rollspeed);
me.rollspeed_diff = math.abs(me.rollspeed - me.filtered_rollspeed);
me.rollspeed_diff_norm = me.rollspeed_diff > 0 ? me.rollspeed_diff / me.rollspeed : 0;
me.spray_factor = me.calc_spray_factor(me.groundspeed_kts);
# touchdown
# - wow changed (previously false)
# - use a filter on touchdown and use this to determine if the smoke is active.
me.touchdown = 0;
if (me.wow != me.lastwow){
if (me.wow){
me.lpf_touchdown.set(math.abs(me.vert_speed));
}
}
else me.filtered_touchdown = me.lpf_touchdown.filter(0);
# touchdown smoke when
# * recently touched down
# * rollspeed must be over the limit
# * friction must be over a limit (no idea why this is 0.7)
# * moving at ground speed > 50kts (not sure about this)
# * not raining
# possibly using ground speed is somewhat irrelevant - but I'm leaving that here
# as it may filter out unwanted smoke.
if (me.filtered_touchdown > 1.0
and me.rollspeed_diff_norm > me.diff_norm
and me.friction_factor > 0.7
and me.groundspeed_kts > 50
and me.rain <me.rain_norm_trigger) {
me.tyresmoke.setValue(1);
me.spray.setValue(0);
me.spraydensity.setValue(0);
} elsif (wow and groundspeed > 5 and rain >= 0.20) {
} elsif (me.wow and me.rain >= me.rain_norm_trigger) {
me.tyresmoke.setValue(0);
me.spray.setValue(1);
me.sprayspeed.setValue(rollspeed * 6);
me.spraydensity.setValue(rain * groundspeed);
me.sprayspeed.setValue(me.rollspeed * 6);
me.spraydensity.setValue(me.rain * me.spray_factor * me.groundspeed_kts);
} else {
me.tyresmoke.setValue(0);
me.spray.setValue(0);
@ -881,19 +949,20 @@ var tyresmoke = {
me.spraydensity.setValue(0);
}
if (me.auto) {
if (wow) {
if (me.wow) {
settimer(func me.update(), 0);
if (me.listener != nil) {
removelistener(me.listener);
me.listener = nil;
}
} elsif (me.listener == nil) {
me.listener = setlistener(me.wow, func me._wowchanged_(), 0, 0);
me.listener = setlistener(me.wow_node, func me._wowchanged_(), 0, 0);
}
}
me.lastwow = me.wow;
},
_wowchanged_: func() {
if (me.wow.getValue()) {
if (me.wow_node.getValue()) {
me.lp.set(0);
me.update();
}