MMFF/AngleBend.h

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//  Copyright (C) 2013-2025 Paolo Tosco and other RDKit contributors
//
//   @@ 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 <RDGeneral/export.h>
#ifndef __RD_MMFFANGLEBEND_H__
#define __RD_MMFFANGLEBEND_H__
 
#include <ForceField/ForceField.h>
#include <ForceField/Contrib.h>
 
namespace ForceFields {
namespace MMFF {
class MMFFBond;
class MMFFAngle;
class MMFFProp;
 
//! The angle-bend term for MMFF
class RDKIT_FORCEFIELD_EXPORT AngleBendContrib : public ForceFieldContrib {
 public:
  AngleBendContrib() {}
  //! Constructor
  AngleBendContrib(ForceField *owner);
  /*! Adds an angle to the contrib
  The angle is between atom1 - atom2 - atom3
 
  \param idx1        index of atom1 in the ForceField's positions
  \param idx2        index of atom2 in the ForceField's positions
  \param idx3        index of atom3 in the ForceField's positions
  \param angleType   MMFF type of the angle (as an unsigned int)
 
  */
  void addTerm(unsigned int idx1, unsigned int idx2,
               unsigned int idx3, const MMFFAngle *mmffAngleParams,
               const MMFFProp *mmffPropParamsCentralAtom);
 
  double getEnergy(double *pos) const override;
  void getGrad(double *pos, double *grad) const override;
  AngleBendContrib *copy() const override {
    return new AngleBendContrib(*this);
  }
 
 private:
  std::vector<bool> d_isLinear;
  std::vector<int16_t> d_at1Idxs, d_at2Idxs, d_at3Idxs;
  std::vector<double> d_ka, d_theta0;
};
namespace Utils {
//! returns the MMFF rest value for an angle
RDKIT_FORCEFIELD_EXPORT double calcAngleRestValue(
    const MMFFAngle *mmffAngleParams);
//! returns the MMFF force constant for an angle
RDKIT_FORCEFIELD_EXPORT double calcAngleForceConstant(
    const MMFFAngle *mmffAngleParams);
//! calculates and returns the cosine of the angle between points p1, p2, p3
RDKIT_FORCEFIELD_EXPORT double calcCosTheta(RDGeom::Point3D p1,
                                            RDGeom::Point3D p2,
                                            RDGeom::Point3D p3, double dist1,
                                            double dist2);
//! calculates and returns the angle bending MMFF energy
RDKIT_FORCEFIELD_EXPORT double calcAngleBendEnergy(const double theta0,
                                                   const double ka,
                                                   bool isLinear,
                                                   const double cosTheta);
RDKIT_FORCEFIELD_EXPORT void calcAngleBendGrad(RDGeom::Point3D *r, double *dist,
                                               double **g, double &dE_dTheta,
                                               double &cosTheta,
                                               double &sinTheta);
}  // namespace Utils
}  // namespace MMFF
}  // namespace ForceFields
#endif