118 lines
3 KiB
C++
118 lines
3 KiB
C++
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// FGAIBallistic - FGAIBase-derived class creates a ballistic object
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//
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// Written by David Culp, started November 2003.
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// - davidculp2@comcast.net
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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., 675 Mass Ave, Cambridge, MA 02139, 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 <simgear/math/point3d.hxx>
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#include <math.h>
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#include "AIBallistic.hxx"
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FGAIBallistic::FGAIBallistic() {
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}
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FGAIBallistic::~FGAIBallistic() {
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}
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bool FGAIBallistic::init() {
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FGAIBase::init();
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vs = sin( elevation * 0.017453293 ) * speed;
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hs = cos( elevation * 0.017453293 ) * speed;
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aero_stabilized = true;
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hdg = azimuth;
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pitch = elevation;
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return true;
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}
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void FGAIBallistic::update(double dt) {
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Run(dt);
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Transform();
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FGAIBase::update(dt);
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}
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void FGAIBallistic::setAzimuth(double az) {
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azimuth = az;
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}
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void FGAIBallistic::setElevation(double el) {
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elevation = el;
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}
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void FGAIBallistic::setStabilization(bool val) {
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aero_stabilized = val;
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}
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void FGAIBallistic::Run(double dt) {
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double speed_north_deg_sec;
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double speed_east_deg_sec;
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double ft_per_deg_lon;
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double ft_per_deg_lat;
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// get size of a degree at this latitude
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ft_per_deg_lat = 366468.96 - 3717.12 * cos(pos.lat() / 57.2958 );
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ft_per_deg_lon = 365228.16 * cos(pos.lat() / 57.2958);
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// the two drag calculations below assume sea-level density,
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// mass of 0.03 slugs, drag coeff of 0.295, frontal area of 0.007 ft2
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// adjust horizontal speed due to drag
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hs -= 0.000082 * hs * hs * dt;
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if ( hs < 0.0 ) hs = 0.0;
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// adjust vertical speed due to drag
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if (vs > 0.0) {
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vs -= 0.000082 * vs * vs * dt;
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} else {
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vs += 0.000082 * vs * vs * dt;
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}
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// convert horizontal speed (fps) to degrees per second
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speed_north_deg_sec = cos( hdg / 57.29577951 ) * hs / ft_per_deg_lat;
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speed_east_deg_sec = sin( hdg / 57.29577951 ) * hs / ft_per_deg_lon;
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// set new position
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pos.setlat( pos.lat() + speed_north_deg_sec * dt);
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pos.setlon( pos.lon() + speed_east_deg_sec * dt);
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// adjust vertical speed for acceleration of gravity
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vs -= 32.17 * dt;
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// adjust altitude (meters)
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altitude += vs * dt * 0.3048;
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pos.setelev(altitude);
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// adjust pitch if aerostabilized
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if (aero_stabilized) pitch = atan2( vs, hs ) * 57.29577951;
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// set destruction flag if altitude less than sea level -1000
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if (altitude < -1000.0) setDie(true);
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}
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