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ImathVecAlgo.h

///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2002, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
// 
// All rights reserved.
// 
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// modification, are permitted provided that the following conditions are
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// *       Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// *       Redistributions in binary form must reproduce the above
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// distribution.
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// its contributors may be used to endorse or promote products derived
// from this software without specific prior written permission. 
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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///////////////////////////////////////////////////////////////////////////



#ifndef INCLUDED_IMATHVECALGO_H
#define INCLUDED_IMATHVECALGO_H

//-------------------------------------------------------------------------
//
//      This file contains algorithms applied to or in conjunction
//      with points (Imath::Vec2 and Imath::Vec3).
//    The assumption made is that these functions are called much
//    less often than the basic point functions or these functions
//    require more support classes.
//
//-------------------------------------------------------------------------

#include <ImathVec.h>
#include <ImathLimits.h>

namespace Imath {


//--------------------------------------------------------------
// Find the projection of vector t onto vector s (Vec2 and Vec3)
//--------------------------------------------------------------

template <class Vec> Vec      project (const Vec &s, const Vec &t);


//----------------------------------------------
// Find a vector which is perpendicular to s and
// in the same plane as s and t (Vec2 and Vec3)
//----------------------------------------------

template <class Vec> Vec      orthogonal (const Vec &s, const Vec &t);


//-----------------------------------------------
// Find the direction of a ray s after reflection
// off a plane with normal t (Vec2 and Vec3)
//-----------------------------------------------

template <class Vec> Vec      reflect (const Vec &s, const Vec &t);


//----------------------------------------------------------------------
// Find the vertex of triangle (v0, v1, v2), which is closest to point p
// (Vec2 and Vec3).
//----------------------------------------------------------------------

template <class Vec> Vec      closestVertex (const Vec &v0,
                                     const Vec &v1,
                                     const Vec &v2, 
                                     const Vec &p);

//---------------
// Implementation
//---------------

template <class Vec>
Vec
project (const Vec &s, const Vec &t)
{
    Vec sNormalized = s.normalized();
    return sNormalized * (sNormalized ^ t);
}

template <class Vec>
Vec
orthogonal (const Vec &s, const Vec &t)
{
    return t - project (s, t);
}

template <class Vec>
Vec
reflect (const Vec &s, const Vec &t)
{
    return s - typename Vec::BaseType(2) * (s - project(t, s));
}

template <class Vec>
Vec
closestVertex(const Vec &v0,
              const Vec &v1,
              const Vec &v2, 
              const Vec &p)
{
    Vec nearest = v0;
    typename Vec::BaseType neardot = (v0 - p).length2();
    typename Vec::BaseType tmp     = (v1 - p).length2();

    if (tmp < neardot)
    {
        neardot = tmp;
        nearest = v1;
    }

    tmp = (v2 - p).length2();

    if (tmp < neardot)
    {
        neardot = tmp;
        nearest = v2;
    }

    return nearest;
}


} // namespace Imath

#endif

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