Parallel

					_SHADING ROUTINES_ 
by Steven Upstill

[LISTING 1]

surface 
marble( float Kd=.5, Ka=.1;
        color veincolor=0)
{
     float khi ;
     point fnormal ;
     color surfcolor ;
     point freq = 4 * P;
     float turbulence = 0;
     float amplitude = 1, octave;

     /* Make sure the eye-vector points the right way */
    fnormal = faceforward( normalize(N), I ) ;

     /* ...