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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),
Length(0.0),
Inertia1(0.0),
Inertia3(0.0),
mTime(0.0),
mDeltaTime(0.0),
mSolver(0)
{
mState[0] = 0.0;
mState[1] = 0.0;
mState[2] = 0.0;
mAux[0] = 0.0;
mAux[1] = 0.0;
mAux[2] = 0.0;
mAux[3] = 0.0;
mAux[4] = 0.0;
}
//----------------------------------------------------------------------------
PhysicsModule::~PhysicsModule ()
{
delete0(mSolver);
}
//----------------------------------------------------------------------------
void PhysicsModule::Initialize (double time, double deltaTime, double theta,
double phi, double psi, double angVel1, double angVel2, double angVel3)
{
mTime = time;
mDeltaTime = deltaTime;
double cosPhi = Mathd::Cos(phi), sinPhi = Mathd::Sin(phi);
double cosPsi = Mathd::Cos(psi), sinPsi = Mathd::Sin(psi);
// state variables
mState[0] = theta;
mState[1] = phi;
mState[2] = psi;
// auxiliary variables
mAux[0] = Mass*Gravity*Length/Inertia1; // alpha
mAux[1] = angVel1*angVel1 + angVel2*angVel2 + 2.0*cosPhi*mAux[0]; // beta
mAux[2] = angVel3*Inertia3/Inertia1; // epsilon
mAux[3] = sinPhi*(angVel1*sinPsi + angVel2*cosPsi) +
cosPhi*mAux[2]; // delta
mAux[4] = angVel3;
// 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(3, mDeltaTime, OdeFunction, mAux);
}
//----------------------------------------------------------------------------
void PhysicsModule::Update ()
{
// Apply a single step of the ODE solver.
if (mSolver)
{
mSolver->Update(mTime, mState, mTime, mState);
}
}
//----------------------------------------------------------------------------
HMatrix PhysicsModule::GetBodyAxes () const
{
float cosTheta = (float)Mathd::Cos(mState[0]);
float sinTheta = (float)Mathd::Sin(mState[0]);
float cosPhi = (float)Mathd::Cos(mState[1]);
float sinPhi = (float)Mathd::Sin(mState[1]);
float cosPsi = (float)Mathd::Cos(mState[2]);
float sinPsi = (float)Mathd::Sin(mState[2]);
AVector N(cosTheta, sinTheta, 0.0f);
AVector axis3(sinTheta*sinPhi, -cosTheta*sinPhi, cosPhi);
AVector axis3xN = axis3.Cross(N);
AVector axis1 = cosPsi*N + sinPsi*axis3xN;
AVector axis2 = cosPsi*axis3xN - sinPsi*N;
return HMatrix(axis1, axis2, axis3, APoint::ORIGIN, true);
}
//----------------------------------------------------------------------------
void PhysicsModule::OdeFunction (double, const double* state, void* data,
double* output)
{
double* aux = (double*)data;
double cs = Mathd::Cos(state[1]);
double invSin = 1.0/Mathd::Sin(state[1]);
double numer = aux[3] - aux[2]*cs;
double fraction = numer*invSin;
double arg = aux[1] - 2.0*aux[0]*cs - fraction*fraction;
double thetaDotFunction = fraction*invSin;
double phiDotFunction = Mathd::Sqrt(Mathd::FAbs(arg));
double psiDotFunction = aux[4] - cs*thetaDotFunction;
// dot(theta) function
output[0] = thetaDotFunction;
// dot(phi) function
output[1] = phiDotFunction;
// dot(psi) function
output[2] = psiDotFunction;
}
//----------------------------------------------------------------------------
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