vec4.C

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/*!
 *  \file Vec4.C
 *  \brief Contains implementations of non-inlined functions for the Vec4 class.
 *  \libgfx Most of the code in this file has been adapted from libgfx.
 *
 */

#include "mlib/points.H"
#include "mlib/global.H"
#include "mlib/vec4.H"

std::ostream &
mlib::operator<<(std::ostream &out, const Vec4& v)
{
   return out <<v[0] <<" " <<v[1] <<" " <<v[2] <<" " <<v[3];
}

std::istream &
mlib::operator>>(std::istream &in, Vec4& v)
{
   return in >> v[0] >> v[1] >> v[2] >> v[3];
}

mlib::Vec4
mlib::cross(const Vec4& a, const Vec4& b, const Vec4& c)
{
   // Code adapted from VecLib4d.c in Graphics Gems V

   double d1 = (b[2] * c[3]) - (b[3] * c[2]);
   double d2 = (b[1] * c[3]) - (b[3] * c[1]);
   double d3 = (b[1] * c[2]) - (b[2] * c[1]);
   double d4 = (b[0] * c[3]) - (b[3] * c[0]);
   double d5 = (b[0] * c[2]) - (b[2] * c[0]);
   double d6 = (b[0] * c[1]) - (b[1] * c[0]);
   
   return Vec4(- a[1] * d1 + a[2] * d2 - a[3] * d3,
                 a[0] * d1 - a[2] * d4 + a[3] * d5,
               - a[0] * d2 + a[1] * d4 - a[3] * d6,
                 a[0] * d3 - a[1] * d5 + a[2] * d6);
}

mlib::Vec3<mlib::Wvec>
mlib::proj(const Vec4& v)
{
   Vec3<Wvec> u(v[0], v[1], v[2]);
   if( v[3]!=1.0 && v[3]!=0.0 ) u /= v[3];
   return u;
}

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