// FGAIThermal - FGAIBase-derived class creates an AI thermal
//
-// Written by David Culp, started Feb 2004.
+// Copyright (C) 2004 David P. Culp - davidculp2@comcast.net
//
-// Copyright (C) 2004 David P. Culp - davidculp2@comcast.net
+// An attempt to refine the thermal shape and behaviour by WooT 2009
+//
+// Copyright (C) 2009 Patrice Poly ( WooT )
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
max_strength = 6.0;
diameter = 0.5;
strength = factor = 0.0;
+ cycle_timer = 60*(rand()%31); // some random in the birth time
+ ground_elev_ft = 0.0;
+ dt_count=0.9;
+ alt=0.0;
}
FGAIThermal::~FGAIThermal() {
FGAIBase::readFromScenario(scFileNode);
setMaxStrength(scFileNode->getDoubleValue("strength-fps", 8.0));
- setDiameter(scFileNode->getDoubleValue("diameter-ft", 0.0)/6076.11549);
- setHeight(scFileNode->getDoubleValue("height-msl", 5000.0));
+ setDiameter(scFileNode->getDoubleValue("diameter-ft", 0.0)/6076.11549);
+ setHeight(scFileNode->getDoubleValue("height-msl", 5000.0));
}
bool FGAIThermal::init(bool search_in_AI_path) {
factor = 8.0 * max_strength / (diameter * diameter * diameter);
setAltitude( height );
+ _surface_wind_from_deg_node =
+ fgGetNode("/environment/config/boundary/entry[0]/wind-from-heading-deg", true);
+ _surface_wind_speed_node =
+ fgGetNode("/environment/config/boundary/entry[0]/wind-speed-kt", true);
+ _aloft_wind_from_deg_node =
+ fgGetNode("/environment/config/aloft/entry[2]/wind-from-heading-deg", true);
+ _aloft_wind_speed_node =
+ fgGetNode("/environment/config/aloft/entry[2]/wind-speed-kt", true);
+ do_agl_calc = 1;
return FGAIBase::init(search_in_AI_path);
}
void FGAIThermal::bind() {
+ props->tie("position/altitude-agl-ft", // for debug and tweak
+ SGRawValuePointer<double>(&altitude_agl_ft));
+ props->tie("alt-rel", // for debug and tweak
+ SGRawValuePointer<double>(&alt_rel));
+ props->tie("time", // for debug and tweak
+ SGRawValuePointer<double>(&time));
+ props->tie("xx", // for debug and tweak
+ SGRawValuePointer<double>(&xx));
+ props->tie("is-forming", // for debug abd tweak
+ SGRawValuePointer<bool>(&is_forming));
+ props->tie("is-formed", // for debug abd tweak
+ SGRawValuePointer<bool>(&is_formed));
+ props->tie("is-dying", // for debug abd tweak
+ SGRawValuePointer<bool>(&is_dying));
+ props->tie("is-dead", // for debug abd tweak
+ SGRawValuePointer<bool>(&is_dead));
FGAIBase::bind();
}
void FGAIThermal::unbind() {
+ props->untie("position/altitude-agl-ft");
+ props->untie("alt-rel");
+ props->untie("time");
+ props->untie("is-forming");
+ props->untie("is-formed");
+ props->untie("is-dying");
+ props->untie("is-dead");
+ props->untie("xx");
FGAIBase::unbind();
}
}
+
+//the formula to get the available portion of VUpMax depending on altitude
+//returns a double between 0 and 1
+double FGAIThermal::get_strength_fac(double alt_frac) {
+
+double PI = 4.0 * atan(1.0);
+double fac = 0.0;
+if ( alt_frac <=0.0 ) { // do submarines get thermals ?
+ fac = 0.0;
+ }
+else if ( ( alt_frac>0.0 ) && (alt_frac<=0.1) ) { // ground layer
+ fac = ( 0.1*( pow( (10.0*alt_frac),10.0) ) );
+ }
+else if ( ( alt_frac>0.1 ) && (alt_frac<=1.0) ) { // main body of the thermal
+ fac = 0.4175 - 0.5825* ( cos ( PI* (1.0-sqrt(alt_frac) ) +PI) ) ;
+ }
+else if ( ( alt_frac >1.0 ) && (alt_frac < 1.1 ) ) { //above the ceiling, but not above the cloud
+ fac = (0.5 * ( 1.0 + cos ( PI*( (-2.0*alt_frac)*5.0 ) ) ) );
+ }
+else if ( alt_frac >= 1.1 ) { //above the cloud
+ fac = 0.0;
+ }
+return fac;
+}
+
+
void FGAIThermal::Run(double dt) {
- //###########################//
- // do calculations for range //
- //###########################//
-
- // copy values from the AIManager
- double user_latitude = manager->get_user_latitude();
- double user_longitude = manager->get_user_longitude();
- double user_altitude = manager->get_user_altitude();
-
- // calculate range to target in feet and nautical miles
- double lat_range = fabs(pos.getLatitudeDeg() - user_latitude) * ft_per_deg_lat;
- double lon_range = fabs(pos.getLongitudeDeg() - user_longitude) * ft_per_deg_lon;
- double range_ft = sqrt(lat_range*lat_range + lon_range*lon_range);
- range = range_ft / 6076.11549;
-
- // Calculate speed of rising air if within range.
- // Air vertical speed is maximum at center of thermal,
- // and decreases to zero at the edge (as distance cubed).
- if (range < (diameter * 0.5)) {
- strength = max_strength - ( range * range * range * factor );
- } else {
- strength = 0.0;
- }
-
- // Stop lift at the top of the thermal (smoothly)
- if (user_altitude > (height + 100.0)) {
- strength = 0.0;
- }
- else if (user_altitude < height) {
- // do nothing
- }
- else {
- strength -= (strength * (user_altitude - height) * 0.01);
- }
+// *****************************************
+// the thermal characteristics and variables
+// *****************************************
+
+cycle_timer += dt ;
+
+// time
+
+// the time needed for the thermal to be completely formed
+double tmin1 = 5.0 ;
+// the time when the thermal begins to die
+double tmin2 = 20.0 ;
+// the time when the thermal is completely dead
+double tmin3 = 25.0;
+double alive_cycle_time = tmin3*60.0;
+//the time of the complete cycle, including a period of inactivity
+double tmin4 = 30.0;
+// some times expressed in a fraction of tmin3;
+double t1 = tmin1/tmin3 ;
+double t2 = tmin2/tmin3 ;
+double t3 = 1.0 ;
+double t4 = tmin4/tmin3;
+// the time elapsed since the thermal was born, in a 0-1 fraction of tmin3
+
+time = cycle_timer/alive_cycle_time;
+//comment above and
+//uncomment below to freeze the time cycle
+ time=0.5;
+
+if ( time >= t4) {
+ cycle_timer = 60*(rand()%31);
+ }
+
+
+//the position of the thermal 'top'
+double thermal_foot_lat = (pos.getLatitudeDeg());
+double thermal_foot_lon = (pos.getLongitudeDeg());
+
+//the max updraft one can expect in this thermal
+double MaxUpdraft=max_strength;
+//the max sink one can expect in this thermal, this is a negative number
+double MinUpdraft=-max_strength*0.25;
+//the fraction of MaxUpdraft one can expect at our height and time
+double maxstrengthavail;
+//max updraft at the user altitude and time
+double v_up_max;
+//min updraft at the user altitude and time, this is a negative number
+double v_up_min;
+double wind_speed;
+
+
+//max radius of the the thermal, including the sink area
+double Rmax = diameter/2.0;
+// 'shaping' of the thermal, the higher, the more conical the thermal- between 0 and 1
+double shaping=0.8;
+//the radius of the thermal at our altitude in FT, including sink
+double Rsink;
+//the relative radius of the thermal where we have updraft, between 0 an 1
+double r_up_frac=0.9;
+//radius of the thermal where we have updraft, in FT
+double Rup;
+//how far are we from the thermal center at our altitude in FEET
+double dist_center;
+
+//the position of the center of the thermal slice at our altitude
+double slice_center_lon;
+double slice_center_lat;
+
+
+
+// **************************************
+// various variables relative to the user
+// **************************************
+
+double user_latitude = manager->get_user_latitude();
+double user_longitude = manager->get_user_longitude();
+double user_altitude = manager->get_user_altitude(); // MSL
+
+//we need to know the thermal foot AGL altitude
+
+
+//we could do this only once, as thermal don't move
+//but then agl info is lost on user reset
+//so we only do this every 10 seconds to save cpu
+dt_count += dt;
+if (dt_count >= 10.0 ) {
+ //double alt;
+ if (getGroundElevationM(SGGeod::fromGeodM(pos, 20000), alt, 0)) {
+ ground_elev_ft = alt * SG_METER_TO_FEET;
+ do_agl_calc = 0;
+ altitude_agl_ft = height - ground_elev_ft ;
+ dt_count = 0.0;
+ }
+}
+
+//user altitude relative to the thermal height, seen AGL from the thermal foot
+if ( user_altitude < 1.0 ) { user_altitude = 1.0 ;}; // an ugly way to avoid NaNs for users at alt 0
+double user_altitude_agl= ( user_altitude - ground_elev_ft ) ;
+alt_rel = user_altitude_agl / altitude_agl_ft;
+
+
+
+//the updraft user feels !
+double Vup;
+
+// *********************
+// environment variables
+// *********************
+
+// the wind heading at the user alt
+double wind_heading_rad;
+
+// the "ambient" sink outside thermals
+double global_sink = -1.0;
+
+// **************
+// some constants
+// **************
+
+double PI = 4.0 * atan(1.0);
+
+
+// ******************
+// thermal main cycle
+// ******************
+
+//we get the max strenght proportion we can expect at the time and altitude, formuled between 0 and 1
+//double xx;
+if (time <= t1) {
+ xx= ( time / t1 );
+ maxstrengthavail = xx* get_strength_fac ( alt_rel / xx );
+
+ is_forming=1;is_formed=0;is_dying=0;is_dead=0;
+
+ }
+else if ( (time > t1) && (time <= t2) ) {
+ maxstrengthavail = get_strength_fac ( (alt_rel) );
+
+ is_forming=0;is_formed=1;is_dying=0;is_dead=0;
+
+ }
+else if ( (time > t2) && (time <= t3) ) {
+ xx= ( ( time - t2) / (1.0 - t2) ) ;
+ maxstrengthavail = get_strength_fac ( alt_rel - xx );
+
+ is_forming=0;is_formed=0;is_dying=1;is_dead=0;
+
+ }
+else {
+ maxstrengthavail = 0.0;
+ is_forming=0;is_formed=0;is_dying=0;is_dead=1;
+
+ }
+
+//we get the diameter of the thermal slice at the user altitude
+//the thermal has a slight conic shape
+
+if ( (alt_rel >= 0.0) && (alt_rel < 1.0 ) ) {
+ Rsink = ( shaping*Rmax ) + ( ( (1.0-shaping)*Rmax*alt_rel ) / altitude_agl_ft ); // in the main thermal body
+ }
+else if ( (alt_rel >=1.0) && (alt_rel < 1.1) ) {
+ Rsink = (Rmax/2.0) * ( 1.0+ cos ( (10.0*PI*alt_rel)-(2.0*PI) ) ); // above the ceiling
+ }
+else {
+ Rsink = 0.0; // above the cloud
+ }
+
+//we get the portion of the diameter that produces lift
+Rup = r_up_frac * Rsink ;
+
+//we now determine v_up_max and VupMin depending on our altitude
+
+v_up_max = maxstrengthavail * MaxUpdraft;
+v_up_min = maxstrengthavail * MinUpdraft;
+
+// Now we know, for current t and alt, v_up_max, VupMin, Rup, Rsink.
+
+// We still need to know how far we are from the thermal center
+
+// To determine the thermal inclinaison in the wind, we use a ugly approximation,
+// in which we say the thermal bends 20° (0.34906 rad ) for 10 kts wind.
+// We move the thermal foot upwind, to keep the cloud model over the "center" at ceiling level.
+// the displacement distance of the center of the thermal slice, at user altitude,
+// and relative to a hipothetical vertical thermal, would be:
+
+// get surface and 9000 ft wind
+
+double ground_wind_from_deg = _surface_wind_from_deg_node->getDoubleValue();
+double ground_wind_speed_kts = _surface_wind_speed_node->getDoubleValue();
+double aloft_wind_from_deg = _aloft_wind_from_deg_node->getDoubleValue();
+double aloft_wind_speed_kts = _aloft_wind_speed_node->getDoubleValue();
+
+double ground_wind_from_rad = (PI/2.0) - PI*( ground_wind_from_deg/180.0);
+double aloft_wind_from_rad = (PI/2.0) - PI*( aloft_wind_from_deg/180.0);
+
+wind_heading_rad= PI+ 0.5*( ground_wind_from_rad + aloft_wind_from_rad );
+
+wind_speed = ground_wind_speed_kts + user_altitude * ( (aloft_wind_speed_kts -ground_wind_speed_kts ) / 9000.0 );
+
+double dt_center_alt = -(tan (0.034906*wind_speed)) * ( altitude_agl_ft-user_altitude_agl );
+
+// now, lets find how far we are from this shifted slice
+
+double dt_slice_lon_FT = ( dt_center_alt * cos ( wind_heading_rad ));
+double dt_slice_lat_FT = ( dt_center_alt * sin ( wind_heading_rad ));
+
+double dt_slice_lon = dt_slice_lon_FT / ft_per_deg_lon;
+double dt_slice_lat = dt_slice_lat_FT / ft_per_deg_lat;
+
+slice_center_lon = thermal_foot_lon + dt_slice_lon;
+slice_center_lat = thermal_foot_lat + dt_slice_lat;
+
+double dist_center_lon = fabs(slice_center_lon - user_longitude)* ft_per_deg_lon;
+double dist_center_lat = fabs(slice_center_lat - user_latitude)* ft_per_deg_lat;
+
+double dist_center_FT = sqrt ( dist_center_lon*dist_center_lon + dist_center_lat*dist_center_lat ); // feet
+
+dist_center = dist_center_FT/ 6076.11549; //nautic miles
+
+
+// Now we can calculate Vup
+
+if ( max_strength >=0.0 ) { // this is a thermal
+
+ if ( ( dist_center >= 0.0 ) && ( dist_center < Rup ) ) { //user is in the updraft area
+ Vup = v_up_max * cos ( dist_center* PI/(2.0*Rup) );
+ }
+ else if ( ( dist_center > Rup ) && ( dist_center <= ((Rup+Rsink)/2.0) ) ) { //user in the 1st half of the sink area
+ Vup = v_up_min * cos (( dist_center - ( Rup+Rsink)/2.0 ) * PI / ( 2.0* ( ( Rup+Rsink)/2.0 -Rup )));
+ }
+ else if ( ( dist_center > ((Rup+Rsink)/2.0) ) && dist_center <= Rsink ) { // user in the 2nd half of the sink area
+ Vup = ( global_sink + v_up_min )/2.0 + ( global_sink - v_up_min )/2.0 *cos ( (dist_center-Rsink) *PI/ ( (Rsink-Rup )/2.0) );
+ }
+ else { // outside the thermal
+ Vup = global_sink;
+ }
+ }
+
+else { // this is a sink, we don't want updraft on the sides, nor do we want to feel sink near or above ceiling and ground
+ if ( alt_rel <=1.1 ) {
+ double fac = ( 1.0 - ( 1.0 - 1.815*alt_rel)*( 1.0 - 1.815*alt_rel) );
+ Vup = fac * (global_sink + ( ( v_up_max - global_sink )/2.0 ) * ( 1.0+cos ( dist_center* PI / Rmax ) )) ;
+ }
+ else { Vup = global_sink; }
}
+//correct for no global sink above clouds and outside thermals
+if ( ( (alt_rel > 1.0) && (alt_rel <1.1)) && ( dist_center > Rsink ) ) {
+ Vup = global_sink * ( 11.0 -10.0 * alt_rel );
+ }
+if ( alt_rel >= 1.1 ) {
+ Vup = 0.0;
+ }
+
+strength = Vup;
+range = dist_center;
+
+}
+
+
+
projects / flightgear.git / blobdiff