// Filename: perlinNoise2.cxx
// Created by:  drose (05Oct05)
//
////////////////////////////////////////////////////////////////////
//
// PANDA 3D SOFTWARE
// Copyright (c) Carnegie Mellon University.  All rights reserved.
//
// All use of this software is subject to the terms of the revised BSD
// license.  You should have received a copy of this license along
// with this source code in a file named "LICENSE."
//
////////////////////////////////////////////////////////////////////

#include "perlinNoise2.h"
#include "cmath.h"

////////////////////////////////////////////////////////////////////
//     Function: PerlinNoise2::noise
//       Access: Published
//  Description: Returns the noise function of the three inputs.
////////////////////////////////////////////////////////////////////
double PerlinNoise2::
noise(const LVecBase2d &value) const {
  // Convert the vector to our local coordinate space.
  LVecBase2d vec = _input_xform.xform_point(value);

  double x = vec._v.v._0;
  double y = vec._v.v._1;

  // Find unit square that contains point.
  double xf = cfloor(x);
  double yf = cfloor(y);

  int X = ((int)xf) & _table_size_mask;
  int Y = ((int)yf) & _table_size_mask;

  // Find relative x,y of point in square.
  x -= xf;
  y -= yf;        

  // Compute fade curves for each of x,y.
  double u = fade(x);
  double v = fade(y);

  // Hash coordinates of the 4 square corners (A, B, A + 1, and B + 1)
  int A = _index[X] + Y;
  int B = _index[X + 1] + Y;
  
  // and add blended results from 4 corners of square.
  double result =
    lerp(v, lerp(u, grad(_index[A], x, y), 
                 grad(_index[B], x - 1, y)), 
         lerp(u, grad(_index[A + 1], x, y - 1), 
              grad(_index[B + 1], x - 1, y - 1)));

  return result;
}

////////////////////////////////////////////////////////////////////
//     Function: PerlinNoise2::init_unscaled_xform
//       Access: Private
//  Description: Come up with a random rotation to apply to the input
//               coordinates. This will reduce the problem of the
//               singularities on the axes, by sending the axes in
//               some crazy direction.
////////////////////////////////////////////////////////////////////
void PerlinNoise2::
init_unscaled_xform() {
  double rot = _randomizer.random_real(360.0f);
  _unscaled_xform = LMatrix3d::rotate_mat(rot);

  // And come up with a random translation too, just so the
  // singularity at (0, 0) is also unpredicatable.
  _unscaled_xform.set_row(2, LVecBase2d(_randomizer.random_real_unit(),
                                        _randomizer.random_real_unit()));
}
