Force_Gravity.h

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#ifndef SimTK_SIMBODY_FORCE_GRAVITY_H_
#define SimTK_SIMBODY_FORCE_GRAVITY_H_

/* -------------------------------------------------------------------------- *
 *                               Simbody(tm)                                  *
 * -------------------------------------------------------------------------- *
 * This is part of the SimTK biosimulation toolkit originating from           *
 * Simbios, the NIH National Center for Physics-Based Simulation of           *
 * Biological Structures at Stanford, funded under the NIH Roadmap for        *
 * Medical Research, grant U54 GM072970. See https://simtk.org/home/simbody.  *
 *                                                                            *
 * Portions copyright (c) 2010-13 Stanford University and the Authors.        *
 * Authors: Michael Sherman                                                   *
 * Contributors:                                                              *
 *                                                                            *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may    *
 * not use this file except in compliance with the License. You may obtain a  *
 * copy of the License at http://www.apache.org/licenses/LICENSE-2.0.         *
 *                                                                            *
 * Unless required by applicable law or agreed to in writing, software        *
 * distributed under the License is distributed on an "AS IS" BASIS,          *
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.   *
 * See the License for the specific language governing permissions and        *
 * limitations under the License.                                             *
 * -------------------------------------------------------------------------- */

#include "SimTKcommon.h"
#include "simbody/internal/Force.h"

namespace SimTK {

class SimTK_SIMBODY_EXPORT Force::Gravity : public Force {
public:


//------------------------------------------------------------------------------


Gravity(GeneralForceSubsystem&          forces, 
        const SimbodyMatterSubsystem&   matter,
        const UnitVec3&                 down,
        Real                            g,
        Real                            zeroHeight = 0);

Gravity(GeneralForceSubsystem&          forces, 
        const SimbodyMatterSubsystem&   matter,
        const Vec3&                     gravity);

Gravity(GeneralForceSubsystem&          forces, 
        const SimbodyMatterSubsystem&   matter,
        Real                            g);
   
Gravity() {}

Gravity& setDefaultBodyIsExcluded(MobilizedBodyIndex mobod, bool isExcluded);

Gravity& setDefaultGravityVector(const Vec3& gravity);

Gravity& setDefaultDownDirection(const UnitVec3& down);
Gravity& setDefaultDownDirection(const Vec3& down)
{   return setDefaultDownDirection(UnitVec3(down)); }

Gravity& setDefaultMagnitude(Real g);

Gravity& setDefaultZeroHeight(Real zeroHeight);

bool getDefaultBodyIsExcluded(MobilizedBodyIndex mobod) const;
Vec3 getDefaultGravityVector() const;
const UnitVec3& getDefaultDownDirection() const;
Real getDefaultMagnitude() const;
Real getDefaultZeroHeight() const;

//------------------------------------------------------------------------------

const Gravity& setBodyIsExcluded(State& state, MobilizedBodyIndex mobod, 
                                bool isExcluded) const;

const Gravity& setGravityVector(State& state, const Vec3& gravity) const;

const Gravity& setDownDirection(State&           state,
                                const UnitVec3&  down) const;
const Gravity& setDownDirection(State&          state,
                                const Vec3&     down) const
{   return setDownDirection(state, UnitVec3(down)); }

const Gravity& setMagnitude(State& state, Real g) const;

const Gravity& setZeroHeight(State& state, Real hz) const;

bool getBodyIsExcluded(const State& state, MobilizedBodyIndex mobod) const;
Vec3 getGravityVector(const State& state) const;
const UnitVec3& getDownDirection(const State& state) const;
Real getMagnitude(const State& state) const;
Real getZeroHeight(const State& state) const;

//------------------------------------------------------------------------------

Real getPotentialEnergy(const State& state) const;

const Vector_<SpatialVec>& getBodyForces(const State& state) const;

const SpatialVec& 
getBodyForce(const State& state, MobilizedBodyIndex mobod) const
{   return getBodyForces(state)[mobod]; }

// Particles aren't supported yet so don't show this in Doxygen.
const Vector_<Vec3>& getParticleForces(const State& state) const;

//------------------------------------------------------------------------------
long long getNumEvaluations() const;

bool isForceCacheValid(const State& state) const;

void invalidateForceCache(const State& state) const;
// Don't show this in Doxygen.
SimTK_INSERT_DERIVED_HANDLE_DECLARATIONS(Gravity, GravityImpl, Force);
};

} // namespace SimTK

#endif // SimTK_SIMBODY_FORCE_GRAVITY_H_