////  BendyLine.cpp//  interface////  Copyright (c) 2013 High Fidelity, Inc. All rights reserved. #include "BendyLine.h"#include "Util.h"#include "world.h" const float DEFAULT_BENDY_LINE_SPRING_FORCE  =  10.0f;const float DEFAULT_BENDY_LINE_TORQUE_FORCE  =  0.1f;const float DEFAULT_BENDY_LINE_DRAG          =  10.0f;const float DEFAULT_BENDY_LINE_LENGTH        =  0.09f;const float DEFAULT_BENDY_LINE_THICKNESS     =  0.03f; BendyLine::BendyLine(){     _springForce   = DEFAULT_BENDY_LINE_SPRING_FORCE;    _torqueForce   = DEFAULT_BENDY_LINE_TORQUE_FORCE;    _drag          = DEFAULT_BENDY_LINE_DRAG;    _length        = DEFAULT_BENDY_LINE_LENGTH;    _thickness     = DEFAULT_BENDY_LINE_THICKNESS;        _gravityForce  = glm::vec3(0.0f, 0.0f, 0.0f);    _basePosition  = glm::vec3(0.0f, 0.0f, 0.0f);	    _baseDirection = glm::vec3(0.0f, 1.0f, 0.0f);      _midPosition   = glm::vec3(0.0f, 0.0f, 0.0f);              _endPosition   = glm::vec3(0.0f, 0.0f, 0.0f);              _midVelocity   = glm::vec3(0.0f, 0.0f, 0.0f);              _endVelocity   = glm::vec3(0.0f, 0.0f, 0.0f);  } void BendyLine::reset() {     _midPosition = _basePosition + _baseDirection * _length * ONE_HALF;              _endPosition = _midPosition  + _baseDirection * _length * ONE_HALF;              _midVelocity = glm::vec3(0.0f, 0.0f, 0.0f);              _endVelocity = glm::vec3(0.0f, 0.0f, 0.0f);  } void BendyLine::update(float deltaTime) {     glm::vec3 midAxis = _midPosition - _basePosition;    glm::vec3 endAxis = _endPosition - _midPosition;     float midLength = glm::length(midAxis);            float endLength = glm::length(endAxis);     glm::vec3 midDirection;    glm::vec3 endDirection;        if (midLength > 0.0f) {        midDirection = midAxis / midLength;    } else {        midDirection = _baseDirection;    }        if (endLength > 0.0f) {        endDirection = endAxis / endLength;    } else {        endDirection = _baseDirection;    }        // add spring force    float midForce = midLength - _length * ONE_HALF;    float endForce = endLength - _length * ONE_HALF;    _midVelocity -= midDirection * midForce * _springForce * deltaTime;    _endVelocity -= endDirection * endForce * _springForce * deltaTime;     // add gravity force        _midVelocity += _gravityForce;    _endVelocity += _gravityForce;     // add torque force    _midVelocity += _baseDirection * _torqueForce * deltaTime;    _endVelocity += midDirection   * _torqueForce * deltaTime;        // add drag force    float momentum = 1.0f - (_drag * deltaTime);    if (momentum < 0.0f) {        _midVelocity = glm::vec3(0.0f, 0.0f, 0.0f);        _endVelocity = glm::vec3(0.0f, 0.0f, 0.0f);    } else {        _midVelocity *= momentum;        _endVelocity *= momentum;    }            // update position by velocity    _midPosition += _midVelocity;    _endPosition += _endVelocity;     // clamp lengths    glm::vec3 newMidVector = _midPosition - _basePosition;    glm::vec3 newEndVector = _endPosition - _midPosition;     float newMidLength = glm::length(newMidVector);    float newEndLength = glm::length(newEndVector);        glm::vec3 newMidDirection;    glm::vec3 newEndDirection;     if (newMidLength > 0.0f) {        newMidDirection = newMidVector/newMidLength;    } else {        newMidDirection = _baseDirection;    }     if (newEndLength > 0.0f) {        newEndDirection = newEndVector/newEndLength;    } else {        newEndDirection = _baseDirection;    }        _endPosition = _midPosition  + newEndDirection * _length * ONE_HALF;    _midPosition = _basePosition + newMidDirection * _length * ONE_HALF;}