// Aqsis
// Copyright 1997 - 2001, Paul C. Gregory
//
// Contact: pgregory@aqsis.org
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public
// License as published by the Free Software Foundation; either
// version 2 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

/** \file
                \brief An imager shader to create film grain
                \author Tristan Colgate-McFarlane (tristan@cream.org)
*/



imager filmgrain ()
{
    // We only apply the grain to the mid range of the image, bright and dark areas don't 
    // get much.
    color CiHSV = ctransform("hsv",Ci);
    float CiV = comp(CiHSV,2);
    float MidV = sin (CiV * PI) / 4;
  
    float grain = float noise (s,t);
    Ci =  Ci * (1 - ( MidV * grain  ) );

    Oi = 1;
    alpha = 1;
}
