mgcmultiplecurve2.cpp

《3D游戏引擎设计》的源码

// Magic Software, Inc.
// http://www.magic-software.com
// Copyright (c) 2000, All Rights Reserved
//
// Source code from Magic Software is supplied under the terms of a license
// agreement and may not be copied or disclosed except in accordance with the
// terms of that agreement.  The various license agreements may be found at
// the Magic Software web site.  This file is subject to the license
//
// FREE SOURCE CODE
// http://www.magic-software.com/License/free.pdf

#include "MgcMultipleCurve2.h"

//----------------------------------------------------------------------------
MgcMultipleCurve2::MgcMultipleCurve2 (int iSegments, MgcReal* afTime)
    :
    MgcMultipleCurve<MgcVector2>(iSegments,afTime)
{
}
//----------------------------------------------------------------------------
MgcVector2 MgcMultipleCurve2::GetNormal (MgcReal fTime) const
{
    MgcVector2 kTangent = GetFirstDerivative(fTime);
    kTangent.Unitize();
    MgcVector2 kNormal = kTangent.Cross();
    return kNormal;
}
//----------------------------------------------------------------------------
void MgcMultipleCurve2::GetFrame (MgcReal fTime, MgcVector2& kPosition,
    MgcVector2& kTangent, MgcVector2& kNormal) const
{
    kPosition = GetPosition(fTime);
    kTangent = GetFirstDerivative(fTime);
    kTangent.Unitize();
    kNormal = kTangent.Cross();
}
//----------------------------------------------------------------------------
MgcReal MgcMultipleCurve2::GetCurvature (MgcReal fTime) const
{
    MgcVector2 kDer1 = GetFirstDerivative(fTime);
    MgcVector2 kDer2 = GetSecondDerivative(fTime);
    MgcReal fSpeedSqr = kDer1.SquaredLength();

    const MgcReal fTolerance = 1e-06;
    if ( fSpeedSqr >= fTolerance )
    {
        MgcReal fNumer = kDer1.x*kDer2.y - kDer1.y*kDer2.x;
        MgcReal fDenom = MgcMath::Pow(fSpeedSqr,1.5);
        return fNumer/fDenom;
    }
    else
    {
        // curvature is indeterminate, just return 0
        return 0.0;
    }
}
//----------------------------------------------------------------------------