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flightgear/src/AIModel/AIShip.cxx

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C++

// FGAIShip - FGAIBase-derived class creates an AI ship
//
// Written by David Culp, started October 2003.
// - davidculp2@comcast.net
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <simgear/math/point3d.hxx>
#include <math.h>
#include "AIShip.hxx"
FGAIShip::FGAIShip() {
hdg_lock = false;
rudder = 0.0;
_type_str = "ship";
}
FGAIShip::~FGAIShip() {
}
bool FGAIShip::init() {
return FGAIBase::init();
}
void FGAIShip::bind() {
FGAIBase::bind();
props->tie("surface-positions/rudder-pos-norm",
SGRawValuePointer<double>(&rudder));
}
void FGAIShip::unbind() {
FGAIBase::unbind();
}
void FGAIShip::update(double dt) {
Run(dt);
Transform();
FGAIBase::update(dt);
}
void FGAIShip::Run(double dt) {
double turn_radius_ft;
double turn_circum_ft;
double speed_north_deg_sec;
double speed_east_deg_sec;
double ft_per_deg_lon;
double ft_per_deg_lat;
double dist_covered_ft;
double alpha;
// get size of a degree at this latitude
ft_per_deg_lat = 366468.96 - 3717.12 * cos(pos.lat()/SG_RADIANS_TO_DEGREES);
ft_per_deg_lon = 365228.16 * cos(pos.lat() / SG_RADIANS_TO_DEGREES);
// adjust speed
double speed_diff = tgt_speed - speed;
if (fabs(speed_diff) > 0.1) {
if (speed_diff > 0.0) speed += 0.1 * dt;
if (speed_diff < 0.0) speed -= 0.1 * dt;
}
// convert speed to degrees per second
speed_north_deg_sec = cos( hdg / SG_RADIANS_TO_DEGREES )
* speed * 1.686 / ft_per_deg_lat;
speed_east_deg_sec = sin( hdg / SG_RADIANS_TO_DEGREES )
* speed * 1.686 / ft_per_deg_lon;
// set new position
pos.setlat( pos.lat() + speed_north_deg_sec * dt);
pos.setlon( pos.lon() + speed_east_deg_sec * dt);
// adjust heading based on current rudder angle
if (rudder != 0.0) {
turn_radius_ft = 0.088362 * speed * speed
/ tan( fabs(rudder) / SG_RADIANS_TO_DEGREES );
turn_circum_ft = SGD_2PI * turn_radius_ft;
dist_covered_ft = speed * 1.686 * dt;
alpha = dist_covered_ft / turn_circum_ft * 360.0;
hdg += alpha * sign( rudder );
if ( hdg > 360.0 ) hdg -= 360.0;
if ( hdg < 0.0) hdg += 360.0;
}
// adjust target rudder angle if heading lock engaged
if (hdg_lock) {
double rudder_sense = 0.0;
double diff = fabs(hdg - tgt_heading);
if (diff > 180) diff = fabs(diff - 360);
double sum = hdg + diff;
if (sum > 360.0) sum -= 360.0;
if (fabs(sum - tgt_heading) < 1.0) {
rudder_sense = 1.0;
} else {
rudder_sense = -1.0;
}
if (diff < 30) tgt_roll = diff * rudder_sense;
}
// adjust rudder angle
double rudder_diff = tgt_roll - rudder;
if (fabs(rudder_diff) > 0.1) {
if (rudder_diff > 0.0) rudder += 5.0 * dt;
if (rudder_diff < 0.0) rudder -= 5.0 * dt;
}
}
void FGAIShip::AccelTo(double speed) {
tgt_speed = speed;
}
void FGAIShip::PitchTo(double angle) {
tgt_pitch = angle;
}
void FGAIShip::RollTo(double angle) {
tgt_roll = angle;
}
void FGAIShip::YawTo(double angle) {
}
void FGAIShip::ClimbTo(double altitude) {
}
void FGAIShip::TurnTo(double heading) {
tgt_heading = heading;
hdg_lock = true;
}
double FGAIShip::sign(double x) {
if ( x < 0.0 ) { return -1.0; }
else { return 1.0; }
}