/* =====================
Distance
======================
**
** This function computes and returns the distance between
a
** point and a plane. Normal points toward out.
*/
double Distance(double x, double y, double z, double w, int
plane )
{
switch( plane )
{
case 0: return( -w -
x );
case 1: return( -w +
x );
case 2: return( -w -
y );
case 3: return( -w +
y );
case 4: return( -w -
z );
case 5: return( -w +
z );
}
return( 0.0 );
}