/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkImplicitHalo.cxx

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
#include "vtkImplicitHalo.h"

#include "vtkMath.h"
#include "vtkObjectFactory.h"
#include <cassert>

vtkStandardNewMacro(vtkImplicitHalo);

//------------------------------------------------------------------------------
vtkImplicitHalo::vtkImplicitHalo()
{
  this->Center[0] = 0.0;
  this->Center[1] = 0.0;
  this->Center[2] = 0.0;
  this->Radius = 1.0;
  this->FadeOut = 0.01;
}

//------------------------------------------------------------------------------
vtkImplicitHalo::~vtkImplicitHalo() = default;

//------------------------------------------------------------------------------
double vtkImplicitHalo::EvaluateFunction(double x[3])
{
  double result;
  double distance = sqrt(vtkMath::Distance2BetweenPoints(this->Center, x));
  if (distance > this->Radius)
  {
    result = 0.0;
  }
  else
  {
    double smallRadius = this->Radius * (1.0 - this->FadeOut);
    if (distance <= smallRadius)
    {
      result = 1.0;
    }
    else
    {
      // here this->FadeOut and this->Radius cannot be 0.0 as they are handled
      // by the cases seen above.
      result = (1.0 - distance / this->Radius) / this->FadeOut;
    }
  }
  return result;
}

//------------------------------------------------------------------------------
void vtkImplicitHalo::EvaluateGradient(double vtkNotUsed(x)[3], double vtkNotUsed(g)[3])
{
  assert("check: TODO" && false);
}

//------------------------------------------------------------------------------
void vtkImplicitHalo::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os, indent);

  os << indent << "Center: " << this->Center[0] << "," << this->Center[1] << "," << this->Center[2]
     << endl;
  os << indent << "Radius: " << this->Radius << endl;
  os << indent << "FadeOut: " << this->FadeOut << endl;
}