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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),
Friction(0.0),
Angle(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;
}
//----------------------------------------------------------------------------
PhysicsModule::~PhysicsModule ()
{
delete0(mSolver);
}
//----------------------------------------------------------------------------
void PhysicsModule::Initialize (double time, double deltaTime, double x,
double w, double xDer, double wDer)
{
mTime = time;
mDeltaTime = deltaTime;
// state variables
mState[0] = x;
mState[1] = xDer;
mState[2] = w;
mState[3] = wDer;
// auxiliary variables
mAux[0] = Friction/Mass;
mAux[1] = Gravity*Mathd::Sin(Angle);
// RK4 differential equation solver. Since m_pkSolver 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);
}
//----------------------------------------------------------------------------
void PhysicsModule::Update ()
{
if (mSolver)
{
// Apply a single step of the ODE solver.
mSolver->Update(mTime, mState, mTime, mState);
}
}
//----------------------------------------------------------------------------
void PhysicsModule::OdeFunction (double, const double* state, void* data,
double* output)
{
double* aux = (double*)data;
double vLen = Mathd::Sqrt(state[1]*state[1] + state[3]*state[3]);
double xDerFunction, wDerFunction;
if (vLen > Mathd::ZERO_TOLERANCE)
{
double temp = -aux[0]/vLen;
xDerFunction = temp*state[1];
wDerFunction = temp*state[3] - aux[1];
}
else
{
// Velocity is effectively zero, so frictional force is zero.
xDerFunction = 0.0;
wDerFunction = -aux[1];
}
// x function
output[0] = state[1];
// dot(x) function
output[1] = xDerFunction;
// w function
output[2] = state[3];
// dot(w) function
output[3] = wDerFunction;
}
//----------------------------------------------------------------------------
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