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// $Id: DistanceConstraint.cpp 1528 2010-09-26 17:04:37Z glandrum $
//
// Copyright (C) 2004-2006 Rational Discovery LLC
//
// @@ All Rights Reserved @@
// This file is part of the RDKit.
// The contents are covered by the terms of the BSD license
// which is included in the file license.txt, found at the root
// of the RDKit source tree.
//
#include "DistanceConstraint.h"
#include <math.h>
#include <ForceField/ForceField.h>
#include <RDGeneral/Invariant.h>
namespace ForceFields {
namespace UFF {
DistanceConstraintContrib::DistanceConstraintContrib(ForceField *owner,
unsigned int idx1,unsigned int idx2,
double minLen,double maxLen,
double forceConst) {
PRECONDITION(owner,"bad owner");
RANGE_CHECK(0,idx1,owner->positions().size()-1);
RANGE_CHECK(0,idx2,owner->positions().size()-1);
PRECONDITION(maxLen>=minLen,"bad bounds");
dp_forceField = owner;
d_end1Idx = idx1;
d_end2Idx = idx2;
d_minLen = minLen;
d_maxLen = maxLen;
d_forceConstant = forceConst;
}
double DistanceConstraintContrib::getEnergy(double *pos) const {
PRECONDITION(dp_forceField,"no owner");
PRECONDITION(pos,"bad vector");
//return 0.0;
double dist=this->dp_forceField->distance(this->d_end1Idx,this->d_end2Idx,pos);
double distTerm=0.0;
if(dist<this->d_minLen){
distTerm=this->d_minLen-dist;
} else if(dist>this->d_maxLen) {
distTerm=dist-this->d_maxLen;
}
double res = 0.5*this->d_forceConstant*distTerm*distTerm;
//std::cerr << "DIST(" << this->d_end1Idx << ","<<this->d_end2Idx << "): " << this->d_maxLen << " " << dist << " E=" << res << std::endl;
return res;
}
void DistanceConstraintContrib::getGrad(double *pos,double *grad) const {
PRECONDITION(dp_forceField,"no owner");
PRECONDITION(pos,"bad vector");
PRECONDITION(grad,"bad vector");
double dist=this->dp_forceField->distance(this->d_end1Idx,this->d_end2Idx,pos);
double preFactor = 0.0;
if(dist<this->d_minLen){
preFactor=dist-this->d_minLen;
} else if(dist>this->d_maxLen) {
preFactor=dist-this->d_maxLen;
} else {
return;
}
preFactor *= this->d_forceConstant;
double *end1Coords = &(pos[3*this->d_end1Idx]);
double *end2Coords = &(pos[3*this->d_end2Idx]);
for(int i=0;i<3;i++){
double dGrad;
if(dist>0.0){
dGrad=preFactor * (end1Coords[i]-end2Coords[i])/dist;
} else {
// FIX: this likely isn't right
dGrad=preFactor * (end1Coords[i]-end2Coords[i]);
}
grad[3*this->d_end1Idx+i] += dGrad;
grad[3*this->d_end2Idx+i] -= dGrad;
}
}
}
}
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