/*
 * Copyright (C) 2003, 2004 Jason Bevins (original libnoise code)
 * Copyright  2010 Thomas J. Hodge (java port of libnoise)
 * 
 * This file is part of libnoiseforjava.
 * 
 * libnoiseforjava is a Java port of the C++ library libnoise, which may be found at 
 * http://libnoise.sourceforge.net/.  libnoise was developed by Jason Bevins, who may be 
 * contacted at jlbezigvins@gmzigail.com (for great email, take off every 'zig').
 * Porting to Java was done by Thomas Hodge, who may be contacted at
 * libnoisezagforjava@gzagmail.com (remove every 'zag').
 * 
 * libnoiseforjava 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 3 of the License, or (at your option) any later version.
 * 
 * libnoiseforjava 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
 * libnoiseforjava.  If not, see <http://www.gnu.org/licenses/>.
 * 
 */

package libnoiseforjava.module;

import libnoiseforjava.Interp;
import libnoiseforjava.exception.ExceptionInvalidParam;

public class Blend extends ModuleBase
{
   /// Noise module that outputs a weighted blend of the output values from
   /// two source modules given the output value supplied by a control module.
   ///
   /// Unlike most other noise modules, the index value assigned to a source
   /// module determines its role in the blending operation:
   /// - Source module 0 outputs one of the
   ///   values to blend.
   /// - Source module 1 outputs one of the
   ///   values to blend.
   /// - Source module 2 is known as the <i>control
   ///   module</i>.  The control module determines the weight of the
   ///   blending operation.  Negative values weigh the blend towards the
   ///   output value from the source module with an index value of 0.
   ///   Positive values weigh the blend towards the output value from the
   ///   source module with an index value of 1.
   ///
   /// An application can pass the control module to the setControlModule()
   /// method instead of the setSourceModule() method.  This may make the
   /// application code easier to read.
   ///
   /// This noise module uses linear interpolation to perform the blending
   /// operation.
   ///
   /// This noise module requires three source modules.

   public Blend (ModuleBase sourceModuleOne, ModuleBase sourceModuleTwo,
         ModuleBase sourceModuleThree) throws ExceptionInvalidParam
   {
      super(3);
      setSourceModule(0, sourceModuleOne);
      setSourceModule(1, sourceModuleTwo);
      setSourceModule(2, sourceModuleThree);
   }

   public double getValue (double x, double y, double z)
   {
      assert (sourceModules[0] != null);
      assert (sourceModules[1] != null);
      assert (sourceModules[2] != null);

      double v0 = sourceModules[0].getValue (x, y, z);
      double v1 = sourceModules[1].getValue (x, y, z);
      double alpha = (sourceModules[2].getValue (x, y, z) + 1.0) / 2.0;

      return Interp.linearInterp (v0, v1, alpha);
   }
}