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Vec4.cc

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/*
    File:           Vec4.cc

    Function:       Implements Vec4.h

    Author(s):      Andrew Willmott

    Copyright:      (c) 1995-2000, Andrew Willmott

    Notes:          

*/


#include "vl/Vec4.h"
#include <ctype.h>
#include <iomanip.h>


TVec4 &TVec4::MakeUnit(Int n, TVReal k)
{
    if (n == 0)
    { elt[0] = k; elt[1] = vl_zero; elt[2] = vl_zero; elt[3] = vl_zero; }
    else if (n == 1)
    { elt[0] = vl_zero; elt[1] = k; elt[2] = vl_zero; elt[3] = vl_zero; }
    else if (n == 2)
    { elt[0] = vl_zero; elt[1] = vl_zero; elt[2] = k; elt[3] = vl_zero; }
    else if (n == 3)
    { elt[0] = vl_zero; elt[1] = vl_zero; elt[2] = vl_zero; elt[3] = k; }
    else 
        _Error("(Vec4::MakeUnit) illegal unit vector");

    return(SELF);
}

Bool TVec4::operator == (const TVec4 &a) const
{
    return(elt[0] == a[0] && elt[1] == a[1] && elt[2] == a[2] && elt[3] == a[3]);
}

Bool TVec4::operator != (const TVec4 &a) const
{
    return(elt[0] != a[0] || elt[1] != a[1] || elt[2] != a[2] || elt[3] != a[3]);
}

TVec4 cross(const TVec4 &a, const TVec4 &b, const TVec4 &c) 
{
    TVec4 result;
    // XXX can this be improved? Look at assembly.
#define ROW(i)       a[i], b[i], c[i]
#define DET(i,j,k)   dot(TVec3(ROW(i)), cross(TVec3(ROW(j)), TVec3(ROW(k))))
    
    result[0] =  DET(1,2,3);
    result[1] = -DET(0,2,3);
    result[2] =  DET(0,1,3);
    result[3] = -DET(0,1,2);
    
    return(result);

#undef ROW
#undef DET
}

TVec3 proj(const TVec4 &v)       
{
    TVec3 result;
    
    Assert(v[3] != 0, "(Vec4/proj) last elt. is zero");
    
    result[0] = v[0] / v[3];
    result[1] = v[1] / v[3];
    result[2] = v[2] / v[3];
    
    return(result);
}


ostream &operator << (ostream &s, const TVec4 &v)
{
    Int w = s.width();
        
    return(s << '[' << v[0] << ' ' << setw(w) << v[1] << ' '
        << setw(w) << v[2] << ' ' << setw(w) << v[3] << ']');
}

istream &operator >> (istream &s, TVec4 &v)
{
    TVec4   result;
    Char    c;
    
    // Expected format: [1 2 3 4]
    
    while (s >> c && isspace(c))        
        ;
        
    if (c == '[')                       
    {
        s >> result[0] >> result[1] >> result[2] >> result[3];  

        if (!s)
        {
            cerr << "Error: Expected number while reading vector\n";
            return(s);
        }
            
        while (s >> c && isspace(c))
            ;
            
        if (c != ']')
        {
            s.clear(ios::failbit);
            cerr << "Error: Expected ']' while reading vector\n";
            return(s);
        }
    }
    else
    {
        s.clear(ios::failbit);
        cerr << "Error: Expected '[' while reading vector\n";
        return(s);
    }
    
    v = result;
    return(s);
}

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