/******************************************************************/
/* This file is part of the homework assignments for CSCI-427/527 */
/* at The College of William & Mary and authored by Pieter Peers. */
/* No part of this file, whether altered or in original form, can */
/* be distributed or used outside the context of CSCI-427/527     */
/* without consent of either the College of William & Mary or     */
/* Pieter Peers.                                                  */
/******************************************************************/
#include <cmath>
#include "constants.h"
#include "spotLightsource.h"

//////////////////
// Constructors //
//////////////////
spotLightsource::spotLightsource(const vec3d& position, const vec3d& direction, float cutoffDegrees, float sharpness, const color& power, const vec3d& attenuation)
{
  _position = position;
  _direction = normalize(direction);
  _cutoff = cos(cutoffDegrees * PI / 180.0f);
  _sharpness = sharpness;
  _power = power;
  _attenuation = attenuation;
}


/////////////
// Methods //
/////////////
lightSample spotLightsource::intensityAt(const vec3d& point) const
{
  vec3d direction = point - _position;
  float distance = direction.length();
  float cosAngle = _direction.dot(direction) / distance;

  // check if outside cone
  if(cosAngle < _cutoff) return lightSample(direction, color(0.0f, 0.0f, 0.0f), distance);

  // compute attenuation & scale
  float attenuation = ((_attenuation[2]*distance + _attenuation[1])*distance + _attenuation[0]);
  float scale = pow(cosAngle, _sharpness);

  // Done.
  return lightSample(direction, _power * scale / attenuation, distance);
}


lightSample spotLightsource::emittanceAt(const vec3d& point, float r1, float r2) const
{
  vec3d direction = point - _position;
  float distance = direction.length();
  float cosAngle = _direction.dot(direction) / distance;

  // compute emittance
  color emittance = (cosAngle < _cutoff) ? color(0.0f, 0.0f, 0.0f) : _power * pow(cosAngle, _sharpness) / (4.0f * PI);

  // Done.
  // PDF = 1.0 => there is only a single point
  // Foreshortening => no normal
  return lightSample(direction, emittance, distance, 1.0f, 1.0f);
}

/////////////////////
// Private Methods //
/////////////////////
void spotLightsource::_print(std::ostream& s) const
{
  s << "Spot Lightsource: position=" << _position << ", direction=" << _direction << ", cutoff=" << (acos(_cutoff)*180.0f/PI) << ", sharpness=" << _sharpness << ", power=" << _power << ", attenuation=" << _attenuation;  
}