tgBulletUnidirComprSpr.h

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/*
 * Copyright © 2012, United States Government, as represented by the
 * Administrator of the National Aeronautics and Space Administration.
 * All rights reserved.
 * 
 * The NASA Tensegrity Robotics Toolkit (NTRT) v1 platform is 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.
*/

#ifndef SRC_CORE_TG_BULLET_UNIDIR_COMPR_SPR_H_
#define SRC_CORE_TG_BULLET_UNIDIR_COMPR_SPR_H_

// The Bullet Physics library
#include "LinearMath/btVector3.h"
// The C++ Standard Library
#include <vector>

// This class inherits from tgBulletCompressionSpring
#include "tgBulletCompressionSpring.h"

// Forward references
// Note that even though this object is not a tgSpringCable,
// we're still using tgSpringCableAnchor as a convenience.
// This works because there actually don't seem to be any references
// to tgSpringCable in tgSpringCableAnchor or tgBulletSpringCableAnchor.
class btRigidBody;
class tgSpringCableAnchor;
class tgBulletSpringCableAnchor;

class tgBulletUnidirComprSpr : public tgBulletCompressionSpring
{
public: 
    tgBulletUnidirComprSpr(
                                const std::vector<tgBulletSpringCableAnchor*>& anchors,
                        bool isFreeEndAttached,
                double coefK,
                double coefD,
                double restLength,
                                btVector3 * direction);
    
    virtual ~tgBulletUnidirComprSpr();

    virtual void step(double dt);

    virtual const double getCurrentAnchorDistanceAlongDirection() const;
    
    virtual const double getCurrentSpringLength() const;

    virtual const btVector3 getSpringEndpoint() const;
    
    virtual const double getSpringForce() const;

    virtual const btVector3 * getDirection() const
    {
        return m_direction;
    }
    
protected:

    btVector3 * m_direction;
    
    virtual void calculateAndApplyForce(double dt);

private: 
    bool invariant(void) const;
};

#endif  // SRC_CORE_TG_BULLET_UNIDIR_COMPR_SPR_H_