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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 "Wm5Math.h"
#include "Wm5Memory.h"
#include "Wm5OdeRungeKutta4.h"
//----------------------------------------------------------------------------
PhysicsModule::PhysicsModule ()
:
Gravity(0.0),
Mass(0.0),
mTime(0.0),
mDeltaTime(0.0),
mSolver(0)
{
mState[0] = 0.0;
mState[1] = 0.0;
mAux[0] = 0.0;
}
//----------------------------------------------------------------------------
PhysicsModule::~PhysicsModule ()
{
delete0(mSolver);
}
//----------------------------------------------------------------------------
void PhysicsModule::Initialize (double time, double deltaTime, double q,
double qDot)
{
mTime = time;
mDeltaTime = deltaTime;
// State variables.
mState[0] = q;
mState[1] = qDot;
// Auxiliary variable.
mAux[0] = Gravity;
// 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(2, mDeltaTime, OdeFunction, mAux);
}
//----------------------------------------------------------------------------
void PhysicsModule::Update ()
{
// Apply a single step of the ODE solver.
if (mSolver)
{
mSolver->Update(mTime, mState, mTime, mState);
}
}
//----------------------------------------------------------------------------
void PhysicsModule::OdeFunction (double, const double* input, void* data,
double* output)
{
double* aux = (double*)data;
double qSqr = input[0]*input[0];
double qDotSqr = input[1]*input[1];
double numer = -3.0*aux[0]*qSqr - 2.0*input[0]*(2.0 + 9.0*qSqr)*qDotSqr;
double denom = 1.0 + qSqr*(4.0 + 9.0*qSqr);
double qDotFunction = numer/denom;
// q function
output[0] = input[1];
// dot(q) function
output[1] = qDotFunction;
}
//----------------------------------------------------------------------------
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