mgcdistvec3cir3.cpp

3D Game Engine Design Source Code非常棒

// 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 "MgcDistVec3Cir3.h"

static const MgcReal gs_fTolerance = 1e-05;

//----------------------------------------------------------------------------
MgcReal MgcSqrDistance (const MgcVector3& rkPoint, const MgcCircle3& rkCircle,
    MgcVector3* pkClosest)
{
    // signed distance from point to plane of circle
    MgcVector3 kDiff0 = rkPoint - rkCircle.Center();
    MgcReal fDist = kDiff0.Dot(rkCircle.N());

    // projection of P-C onto plane is Q-C = P-C - (fDist)*N
    MgcVector3 kDiff1 = kDiff0 - fDist*rkCircle.N();
    MgcReal fSqrLen = kDiff1.SquaredLength();
    MgcVector3 kClosest;
    MgcReal fSqrDist;

    if ( fSqrLen >= gs_fTolerance )
    {
        kClosest = rkCircle.Center() +
            (rkCircle.Radius()/MgcMath::Sqrt(fSqrLen))*kDiff1;
        MgcVector3 kDiff2 = rkPoint - kClosest;
        fSqrDist = kDiff2.SquaredLength();
    }
    else
    {
        kClosest = MgcVector3(MgcMath::INFINITY,MgcMath::INFINITY,
            MgcMath::INFINITY);
        fSqrDist = rkCircle.Radius()*rkCircle.Radius()+fDist*fDist;
    }

    if ( pkClosest )
        *pkClosest = kClosest;

    return fSqrDist;
}
//----------------------------------------------------------------------------
MgcReal MgcSqrDistance (const MgcVector3& rkPoint, const MgcDisk3& rkDisk,
    MgcVector3* pkClosest)
{
    // signed distance from point to plane of rkDisk
    MgcVector3 kDiff0 = rkPoint - rkDisk.Center();
    MgcReal fDist = kDiff0.Dot(rkDisk.N());

    // projection of P-C onto plane is Q-C = P-C - (fDist)*N
    MgcVector3 kDiff1 = kDiff0 - fDist*rkDisk.N();
    MgcReal fSqrLen = kDiff1.SquaredLength();
    MgcVector3 kClosest;
    MgcReal fSqrDist;

    if ( fSqrLen <= rkDisk.Radius()*rkDisk.Radius() )
    {
        // projected point Q is in disk and is closest to P
        kClosest = rkDisk.Center() + kDiff1;
        fSqrDist = fDist;
    }
    else
    {
        // projected point Q is outside disk, closest point is on circle
        kClosest = rkDisk.Center() +
            (rkDisk.Radius()/MgcMath::Sqrt(fSqrLen))*kDiff1;
        MgcVector3 kDiff2 = rkPoint - kClosest;
        fSqrDist = kDiff2.SquaredLength();
    }

    if ( pkClosest )
        *pkClosest = kClosest;

    return fSqrDist;
}
//----------------------------------------------------------------------------
MgcReal MgcDistance (const MgcVector3& rkPoint, const MgcCircle3& rkCircle,
    MgcVector3* pkClosest)
{
    return MgcMath::Sqrt(MgcSqrDistance(rkPoint,rkCircle,pkClosest));
}
//----------------------------------------------------------------------------
MgcReal MgcDistance (const MgcVector3& rkPoint, const MgcDisk3& rkDisk,
    MgcVector3* pkClosest)
{
    return MgcMath::Sqrt(MgcSqrDistance(rkPoint,rkDisk,pkClosest));
}
//----------------------------------------------------------------------------