384 lines
12 KiB
C++
384 lines
12 KiB
C++
// FGAIThermal - FGAIBase-derived class creates an AI thermal
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//
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// Copyright (C) 2004 David P. Culp - davidculp2@comcast.net
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//
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// An attempt to refine the thermal shape and behaviour by WooT 2009
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//
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// Copyright (C) 2009 Patrice Poly ( WooT )
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as
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// published by the Free Software Foundation; either version 2 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <Main/fg_props.hxx>
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#include <Main/globals.hxx>
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#include <Scenery/scenery.hxx>
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#include <string>
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#include <cmath>
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using std::string;
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#include "AIThermal.hxx"
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FGAIThermal::FGAIThermal() :
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FGAIBase(otThermal, false)
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{
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max_strength = 6.0;
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diameter = 0.5;
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strength = factor = 0.0;
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cycle_timer = 60*(rand()%31); // some random in the birth time
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ground_elev_ft = 0.0;
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dt_count=0.9;
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alt=0.0;
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}
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FGAIThermal::~FGAIThermal() {
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}
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void FGAIThermal::readFromScenario(SGPropertyNode* scFileNode) {
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if (!scFileNode)
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return;
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FGAIBase::readFromScenario(scFileNode);
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setMaxStrength(scFileNode->getDoubleValue("strength-fps", 8.0));
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setDiameter(scFileNode->getDoubleValue("diameter-ft", 0.0)/6076.11549);
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setHeight(scFileNode->getDoubleValue("height-msl", 5000.0));
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}
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bool FGAIThermal::init(bool search_in_AI_path) {
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factor = 8.0 * max_strength / (diameter * diameter * diameter);
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setAltitude( height );
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_surface_wind_from_deg_node =
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fgGetNode("/environment/config/boundary/entry[0]/wind-from-heading-deg", true);
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_surface_wind_speed_node =
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fgGetNode("/environment/config/boundary/entry[0]/wind-speed-kt", true);
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_aloft_wind_from_deg_node =
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fgGetNode("/environment/config/aloft/entry[2]/wind-from-heading-deg", true);
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_aloft_wind_speed_node =
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fgGetNode("/environment/config/aloft/entry[2]/wind-speed-kt", true);
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do_agl_calc = 1;
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return FGAIBase::init(search_in_AI_path);
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}
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void FGAIThermal::bind() {
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FGAIBase::bind();
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tie("position/altitude-agl-ft", // for debug and tweak
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SGRawValuePointer<double>(&altitude_agl_ft));
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tie("alt-rel", // for debug and tweak
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SGRawValuePointer<double>(&alt_rel));
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tie("time", // for debug and tweak
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SGRawValuePointer<double>(&time));
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tie("xx", // for debug and tweak
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SGRawValuePointer<double>(&xx));
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tie("is-forming", // for debug abd tweak
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SGRawValuePointer<bool>(&is_forming));
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tie("is-formed", // for debug abd tweak
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SGRawValuePointer<bool>(&is_formed));
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tie("is-dying", // for debug abd tweak
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SGRawValuePointer<bool>(&is_dying));
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tie("is-dead", // for debug abd tweak
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SGRawValuePointer<bool>(&is_dead));
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}
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void FGAIThermal::update(double dt) {
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FGAIBase::update(dt);
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Run(dt);
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Transform();
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}
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//the formula to get the available portion of VUpMax depending on altitude
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//returns a double between 0 and 1
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double FGAIThermal::get_strength_fac(double alt_frac) {
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double PI = 4.0 * atan(1.0);
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double fac = 0.0;
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if ( alt_frac <=0.0 ) { // do submarines get thermals ?
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fac = 0.0;
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}
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else if ( ( alt_frac>0.0 ) && (alt_frac<=0.1) ) { // ground layer
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fac = ( 0.1*( pow( (10.0*alt_frac),10.0) ) );
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}
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else if ( ( alt_frac>0.1 ) && (alt_frac<=1.0) ) { // main body of the thermal
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fac = 0.4175 - 0.5825* ( cos ( PI* (1.0-sqrt(alt_frac) ) +PI) ) ;
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}
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else if ( ( alt_frac >1.0 ) && (alt_frac < 1.1 ) ) { //above the ceiling, but not above the cloud
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fac = (0.5 * ( 1.0 + cos ( PI*( (-2.0*alt_frac)*5.0 ) ) ) );
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}
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else if ( alt_frac >= 1.1 ) { //above the cloud
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fac = 0.0;
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}
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return fac;
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}
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void FGAIThermal::Run(double dt) {
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// *****************************************
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// the thermal characteristics and variables
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// *****************************************
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cycle_timer += dt ;
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// time
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// the time needed for the thermal to be completely formed
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double tmin1 = 5.0 ;
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// the time when the thermal begins to die
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double tmin2 = 20.0 ;
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// the time when the thermal is completely dead
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double tmin3 = 25.0;
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double alive_cycle_time = tmin3*60.0;
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//the time of the complete cycle, including a period of inactivity
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double tmin4 = 30.0;
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// some times expressed in a fraction of tmin3;
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double t1 = tmin1/tmin3 ;
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double t2 = tmin2/tmin3 ;
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double t3 = 1.0 ;
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double t4 = tmin4/tmin3;
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// the time elapsed since the thermal was born, in a 0-1 fraction of tmin3
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time = cycle_timer/alive_cycle_time;
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//comment above and
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//uncomment below to freeze the time cycle
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time=0.5;
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if ( time >= t4) {
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cycle_timer = 60*(rand()%31);
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}
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//the position of the thermal 'top'
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double thermal_foot_lat = (pos.getLatitudeDeg());
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double thermal_foot_lon = (pos.getLongitudeDeg());
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//the max updraft one can expect in this thermal
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double MaxUpdraft=max_strength;
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//the max sink one can expect in this thermal, this is a negative number
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double MinUpdraft=-max_strength*0.25;
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//the fraction of MaxUpdraft one can expect at our height and time
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double maxstrengthavail;
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//max updraft at the user altitude and time
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double v_up_max;
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//min updraft at the user altitude and time, this is a negative number
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double v_up_min;
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double wind_speed;
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//max radius of the the thermal, including the sink area
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double Rmax = diameter/2.0;
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// 'shaping' of the thermal, the higher, the more conical the thermal- between 0 and 1
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double shaping=0.8;
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//the radius of the thermal at our altitude in FT, including sink
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double Rsink;
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//the relative radius of the thermal where we have updraft, between 0 an 1
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double r_up_frac=0.9;
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//radius of the thermal where we have updraft, in FT
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double Rup;
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//how far are we from the thermal center at our altitude in FEET
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double dist_center;
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//the position of the center of the thermal slice at our altitude
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double slice_center_lon;
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double slice_center_lat;
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//we need to know the thermal foot AGL altitude
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//we could do this only once, as thermal don't move
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//but then agl info is lost on user reset
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//so we only do this every 10 seconds to save cpu
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dt_count += dt;
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if (dt_count >= 10.0 ) {
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//double alt;
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if (getGroundElevationM(SGGeod::fromGeodM(pos, 20000), alt, 0)) {
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ground_elev_ft = alt * SG_METER_TO_FEET;
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do_agl_calc = 0;
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altitude_agl_ft = height - ground_elev_ft ;
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dt_count = 0.0;
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}
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}
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//user altitude relative to the thermal height, seen AGL from the thermal foot
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double user_altitude = globals->get_aircraft_position().getElevationFt();
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if ( user_altitude < 1.0 ) { user_altitude = 1.0 ;}; // an ugly way to avoid NaNs for users at alt 0
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double user_altitude_agl= ( user_altitude - ground_elev_ft ) ;
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alt_rel = user_altitude_agl / altitude_agl_ft;
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//the updraft user feels !
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double Vup;
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// *********************
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// environment variables
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// *********************
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// the wind heading at the user alt
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double wind_heading_rad;
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// the "ambient" sink outside thermals
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double global_sink = -1.0;
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// **************
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// some constants
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// **************
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double PI = 4.0 * atan(1.0);
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// ******************
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// thermal main cycle
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// ******************
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//we get the max strenght proportion we can expect at the time and altitude, formuled between 0 and 1
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//double xx;
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if (time <= t1) {
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xx= ( time / t1 );
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maxstrengthavail = xx* get_strength_fac ( alt_rel / xx );
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is_forming=1;is_formed=0;is_dying=0;is_dead=0;
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}
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else if ( (time > t1) && (time <= t2) ) {
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maxstrengthavail = get_strength_fac ( (alt_rel) );
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is_forming=0;is_formed=1;is_dying=0;is_dead=0;
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}
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else if ( (time > t2) && (time <= t3) ) {
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xx= ( ( time - t2) / (1.0 - t2) ) ;
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maxstrengthavail = get_strength_fac ( alt_rel - xx );
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is_forming=0;is_formed=0;is_dying=1;is_dead=0;
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}
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else {
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maxstrengthavail = 0.0;
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is_forming=0;is_formed=0;is_dying=0;is_dead=1;
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}
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//we get the diameter of the thermal slice at the user altitude
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//the thermal has a slight conic shape
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if ( (alt_rel >= 0.0) && (alt_rel < 1.0 ) ) {
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Rsink = ( shaping*Rmax ) + ( ( (1.0-shaping)*Rmax*alt_rel ) / altitude_agl_ft ); // in the main thermal body
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}
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else if ( (alt_rel >=1.0) && (alt_rel < 1.1) ) {
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Rsink = (Rmax/2.0) * ( 1.0+ cos ( (10.0*PI*alt_rel)-(2.0*PI) ) ); // above the ceiling
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}
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else {
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Rsink = 0.0; // above the cloud
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}
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//we get the portion of the diameter that produces lift
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Rup = r_up_frac * Rsink ;
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//we now determine v_up_max and VupMin depending on our altitude
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v_up_max = maxstrengthavail * MaxUpdraft;
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v_up_min = maxstrengthavail * MinUpdraft;
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// Now we know, for current t and alt, v_up_max, VupMin, Rup, Rsink.
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// We still need to know how far we are from the thermal center
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// To determine the thermal inclinaison in the wind, we use a ugly approximation,
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// in which we say the thermal bends 20° (0.34906 rad ) for 10 kts wind.
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// We move the thermal foot upwind, to keep the cloud model over the "center" at ceiling level.
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// the displacement distance of the center of the thermal slice, at user altitude,
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// and relative to a hipothetical vertical thermal, would be:
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// get surface and 9000 ft wind
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double ground_wind_from_deg = _surface_wind_from_deg_node->getDoubleValue();
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double ground_wind_speed_kts = _surface_wind_speed_node->getDoubleValue();
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double aloft_wind_from_deg = _aloft_wind_from_deg_node->getDoubleValue();
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double aloft_wind_speed_kts = _aloft_wind_speed_node->getDoubleValue();
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double ground_wind_from_rad = (PI/2.0) - PI*( ground_wind_from_deg/180.0);
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double aloft_wind_from_rad = (PI/2.0) - PI*( aloft_wind_from_deg/180.0);
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wind_heading_rad= PI+ 0.5*( ground_wind_from_rad + aloft_wind_from_rad );
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wind_speed = ground_wind_speed_kts + user_altitude * ( (aloft_wind_speed_kts -ground_wind_speed_kts ) / 9000.0 );
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double dt_center_alt = -(tan (0.034906*wind_speed)) * ( altitude_agl_ft-user_altitude_agl );
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// now, lets find how far we are from this shifted slice
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double dt_slice_lon_FT = ( dt_center_alt * cos ( wind_heading_rad ));
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double dt_slice_lat_FT = ( dt_center_alt * sin ( wind_heading_rad ));
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double dt_slice_lon = dt_slice_lon_FT / ft_per_deg_lon;
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double dt_slice_lat = dt_slice_lat_FT / ft_per_deg_lat;
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slice_center_lon = thermal_foot_lon + dt_slice_lon;
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slice_center_lat = thermal_foot_lat + dt_slice_lat;
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dist_center = SGGeodesy::distanceNm(SGGeod::fromDeg(slice_center_lon, slice_center_lat),
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globals->get_aircraft_position());
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// Now we can calculate Vup
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if ( max_strength >=0.0 ) { // this is a thermal
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if ( ( dist_center >= 0.0 ) && ( dist_center < Rup ) ) { //user is in the updraft area
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Vup = v_up_max * cos ( dist_center* PI/(2.0*Rup) );
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}
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else if ( ( dist_center > Rup ) && ( dist_center <= ((Rup+Rsink)/2.0) ) ) { //user in the 1st half of the sink area
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Vup = v_up_min * cos (( dist_center - ( Rup+Rsink)/2.0 ) * PI / ( 2.0* ( ( Rup+Rsink)/2.0 -Rup )));
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}
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else if ( ( dist_center > ((Rup+Rsink)/2.0) ) && dist_center <= Rsink ) { // user in the 2nd half of the sink area
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Vup = ( global_sink + v_up_min )/2.0 + ( global_sink - v_up_min )/2.0 *cos ( (dist_center-Rsink) *PI/ ( (Rsink-Rup )/2.0) );
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}
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else { // outside the thermal
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Vup = global_sink;
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}
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}
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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
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if ( alt_rel <=1.1 ) {
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double fac = ( 1.0 - ( 1.0 - 1.815*alt_rel)*( 1.0 - 1.815*alt_rel) );
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Vup = fac * (global_sink + ( ( v_up_max - global_sink )/2.0 ) * ( 1.0+cos ( dist_center* PI / Rmax ) )) ;
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}
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else { Vup = global_sink; }
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}
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//correct for no global sink above clouds and outside thermals
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if ( ( (alt_rel > 1.0) && (alt_rel <1.1)) && ( dist_center > Rsink ) ) {
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Vup = global_sink * ( 11.0 -10.0 * alt_rel );
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}
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if ( alt_rel >= 1.1 ) {
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Vup = 0.0;
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}
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strength = Vup;
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range = dist_center;
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}
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