mgcintrplncyln.cpp

来自「《3D游戏引擎设计》的源码」· C++ 代码 · 共 79 行

// 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 "MgcIntrPlnCyln.h"

static const MgcReal gs_fEpsilon = 1e-06;

//----------------------------------------------------------------------------
bool MgcTestIntersection (const MgcPlane& rkPlane,
    const MgcCylinder& rkCylinder, bool bUnitNormal)
{
    MgcVector3 kNormal = rkPlane.Normal();
    MgcReal fConstant = rkPlane.Constant();
    if ( !bUnitNormal )
    {
        MgcReal fLength = kNormal.Unitize();
        fConstant /= fLength;
    }

    MgcReal fSDist = kNormal.Dot(rkCylinder.Center()) - fConstant;

    MgcReal fNdW = kNormal.Dot(rkCylinder.Direction());
    if ( MgcMath::Abs(fNdW) > gs_fEpsilon )
    {
        MgcReal fDiscr = 1.0 - fNdW*fNdW;
        MgcReal fRoot = MgcMath::Sqrt(MgcMath::Abs(fDiscr));
        MgcReal fMin = -fSDist - fRoot;
        MgcReal fMax = -fSDist + fRoot;
        MgcReal fHalfHeight = 0.5*rkCylinder.Height();
        return fMin <= fHalfHeight && fMax >= -fHalfHeight;
    }
    else
    {
        return MgcMath::Abs(fSDist) <= rkCylinder.Radius();
    }
}
//----------------------------------------------------------------------------
bool MgcCulled (const MgcPlane& rkPlane, const MgcCylinder& rkCylinder,
    bool bUnitNormal)
{
    MgcVector3 kNormal = rkPlane.Normal();
    MgcReal fConstant = rkPlane.Constant();
    if ( !bUnitNormal )
    {
        MgcReal fLength = kNormal.Unitize();
        fConstant /= fLength;
    }

    MgcReal fSDist = kNormal.Dot(rkCylinder.Center()) - fConstant;

    MgcReal fNdW = kNormal.Dot(rkCylinder.Direction());
    if ( MgcMath::Abs(fNdW) > gs_fEpsilon )
    {
        MgcReal fDiscr = 1.0 - fNdW*fNdW;
        MgcReal fRoot = MgcMath::Sqrt(MgcMath::Abs(fDiscr));
        MgcReal fMin = -fSDist - fRoot;
        MgcReal fMax = -fSDist + fRoot;
        MgcReal fHalfHeight = 0.5*rkCylinder.Height();
        if ( fMin <= fHalfHeight && fMax >= -fHalfHeight )
            return fSDist <= -rkCylinder.Radius();
        else
            return false;
    }
    else
    {
        return fSDist <= -rkCylinder.Radius();
    }
}
//----------------------------------------------------------------------------