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/* This file is part of StepCore library.
Copyright (C) 2007 Vladimir Kuznetsov <ks.vladimir@gmail.com>
StepCore library 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.
StepCore library 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 StepCore; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "coulombforce.h"
#include "particle.h"
#include <cmath>
#include <QtGlobal>
namespace StepCore {
STEPCORE_META_OBJECT(CoulombForce, QT_TRANSLATE_NOOP("ObjectClass", "CoulombForce"), QT_TR_NOOP("Coulomb force"), 0,
STEPCORE_SUPER_CLASS(Item) STEPCORE_SUPER_CLASS(Force),
STEPCORE_PROPERTY_RW(double, coulombConst, QT_TRANSLATE_NOOP("PropertyName", "coulombConst"), STEPCORE_FROM_UTF8(QT_TRANSLATE_NOOP("Units", "N m²/C²")),
QT_TR_NOOP("Coulomb constant"), coulombConst, setCoulombConst))
STEPCORE_META_OBJECT(CoulombForceErrors, QT_TRANSLATE_NOOP("ObjectClass", "CoulombForceErrors"), QT_TR_NOOP("Errors class for CoulombForce"), 0,
STEPCORE_SUPER_CLASS(ObjectErrors),
STEPCORE_PROPERTY_RW(double, coulombConstVariance, QT_TRANSLATE_NOOP("PropertyName", "coulombConstVariance"), STEPCORE_FROM_UTF8(QT_TRANSLATE_NOOP("Units", "N m²/C²")),
QT_TR_NOOP("Coulomb constant variance"), coulombConstVariance, setCoulombConstVariance))
CoulombForce* CoulombForceErrors::coulombForce() const
{
return static_cast<CoulombForce*>(owner());
}
CoulombForce::CoulombForce(double coulombConst)
: Force()
, _coulombConst(coulombConst)
{
coulombForceErrors()->setCoulombConstVariance(square(Constants::CoulombError));
}
void CoulombForce::calcForce(bool calcVariances)
{
const BodyList::const_iterator end = world()->bodies().end();
for(BodyList::const_iterator b1 = world()->bodies().begin(); b1 != end; ++b1) {
if(!(*b1)->metaObject()->inherits<ChargedParticle>()) continue;
for(BodyList::const_iterator b2 = b1+1; b2 != end; ++b2) {
if(!(*b2)->metaObject()->inherits<ChargedParticle>()) continue;
ChargedParticle* p1 = static_cast<ChargedParticle*>(*b1);
ChargedParticle* p2 = static_cast<ChargedParticle*>(*b2);
Vector2d r = p2->position() - p1->position();
double rnorm2 = r.squaredNorm();
Vector2d force = _coulombConst* p1->charge() * p2->charge() * r / (rnorm2*sqrt(rnorm2));
p2->applyForce(force);
force = -force;
p1->applyForce(force);
if(calcVariances) {
// XXX: CHECKME
ChargedParticleErrors* pe1 = p1->chargedParticleErrors();
ChargedParticleErrors* pe2 = p2->chargedParticleErrors();
Vector2d rV = pe2->positionVariance() + pe1->positionVariance();
double chargeVariance = coulombForceErrors()->_coulombConstVariance / square(_coulombConst) +
pe1->chargeVariance() / square(p1->charge()) +
pe2->chargeVariance() / square(p2->charge());
Vector2d forceV = force.array().square()* (
Vector2d(chargeVariance, chargeVariance) +
Vector2d(rV[0] * square(1/r[0] - 3*r[0]/rnorm2) + rV[1] * square(3*r[1]/rnorm2),
rV[1] * square(1/r[1] - 3*r[1]/rnorm2) + rV[0] * square(3*r[0]/rnorm2))).array();
pe1->applyForceVariance(forceV);
pe2->applyForceVariance(forceV);
}
}
}
}
} // namespace StepCore
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