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// Geometric Tools, LLC
// Copyright (c) 1998-2014
// Distributed under the Boost Software License, Version 1.0.
// http://www.boost.org/LICENSE_1_0.txt
// http://www.geometrictools.com/License/Boost/LICENSE_1_0.txt
//
// File Version: 5.0.0 (2010/01/01)
#include "PhysicsModule.h"
#include "Wm5OdeRungeKutta4.h"
#include "Wm5Math.h"
#include "Wm5Memory.h"
//----------------------------------------------------------------------------
PhysicsModule::PhysicsModule ()
:
AngularSpeed(0.0),
Latitude(0.0),
GDivL(0.0),
mTime(0.0),
mDeltaTime(0.0),
mSolver(0)
{
mState[0] = 0.0;
mState[1] = 0.0;
mState[2] = 0.0;
mState[3] = 0.0;
mAux[0] = 0.0;
mAux[1] = 0.0;
mAux[2] = 0.0;
}
//----------------------------------------------------------------------------
PhysicsModule::~PhysicsModule ()
{
delete0(mSolver);
}
//----------------------------------------------------------------------------
void PhysicsModule::Initialize (double time, double deltaTime, double theta,
double phi, double thetaDot, double phiDot)
{
mTime = time;
mDeltaTime = deltaTime;
// state variables
mState[0] = theta;
mState[1] = thetaDot;
mState[2] = phi;
mState[3] = phiDot;
// auxiliary variables
mAux[0] = AngularSpeed*Mathd::Sin(Latitude); // w*sin(lat)
mAux[1] = AngularSpeed*Mathd::Cos(Latitude); // w*cos(lat)
mAux[2] = GDivL;
// RK4 differential equation solver. Since mSolver is a base class
// pointer, you can instead create a solver of whatever class you prefer.
delete0(mSolver);
mSolver = new0 OdeRungeKutta4d(4, mDeltaTime, OdeFunction, mAux);
}
//----------------------------------------------------------------------------
HMatrix PhysicsModule::GetOrientation () const
{
float cosTheta = (float)Mathd::Cos(mState[0]);
float sinTheta = (float)Mathd::Sin(mState[0]);
float sinPhi = (float)Mathd::Sin(mState[2]);
float cosPhi = (float)Mathd::Cos(mState[2]);
float oneMinusCosPhi = 1.0f - cosPhi;
HMatrix rot;
rot[0][0] = 1.0f - oneMinusCosPhi*cosTheta*cosTheta;
rot[0][1] = -oneMinusCosPhi*sinTheta*cosTheta;
rot[0][2] = -sinPhi*cosTheta;
rot[0][3] = 0.0f;
rot[1][0] = rot[0][1];
rot[1][1] = 1.0f - oneMinusCosPhi*sinTheta*sinTheta;
rot[1][2] = -sinPhi*sinTheta;
rot[1][3] = 0.0f;
rot[2][0] = -rot[0][2];
rot[2][1] = -rot[1][2];
rot[2][2] = cosPhi;
rot[2][3] = 0.0f;
rot[3][0] = 0.0f;
rot[3][1] = 0.0f;
rot[3][2] = 0.0f;
rot[3][3] = 1.0f;
return rot;
}
//----------------------------------------------------------------------------
void PhysicsModule::Update ()
{
// Apply a single step to the ODE solver.
if (mSolver)
{
mSolver->Update(mTime, mState, mTime, mState);
}
}
//----------------------------------------------------------------------------
void PhysicsModule::OdeFunction (double, const double* state,
void* data, double* output)
{
double* aux = (double*)data;
double sinTheta = Mathd::Sin(state[0]);
double sinPhi = Mathd::Sin(state[2]);
double cosPhi = Mathd::Cos(state[2]);
// This function has a removable discontinuity at phi = 0. When sin(phi)
// is nearly zero, switch to the function that is defined at phi = 0.
double theta1DotFunction;
if (Mathd::FAbs(sinPhi) < 1e-06)
{
theta1DotFunction = (2.0/3.0)*aux[1]*state[3]*sinTheta;
}
else
{
theta1DotFunction = -2.0*state[3]*(-aux[1]*sinTheta +
cosPhi*(state[1]+aux[0])/sinPhi);
}
double theta2DotFunction = sinPhi*(state[1]*state[1]*cosPhi +
2.0*state[1]*(aux[1]*sinTheta*sinPhi - aux[0]*cosPhi) - aux[2]);
// theta function
output[0] = state[1];
// dot(theta) function
output[1] = theta1DotFunction;
// phi function
output[2] = state[3];
// dot(phi) function
output[3] = theta2DotFunction;
}
//----------------------------------------------------------------------------
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