/******************************************************************/
/* 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
{
  // HW5: Implement this. Computes the intensity from a spot
  //      light source toward the 'point' taking in account
  //      attenuation, cutoff angle, and sharpness.
  // Modifies: nothing.
  // Returns: light sample (pass 1) direction, 2) power/color
  //          of the incident lighting, and 3) distance between
  //          the light source and the point).
  vec3d direction = (point - _position).normalize();
  float dl_dot = direction.dot(_direction);
  float distance = _position.distance(point);
  color emittance;

  if (dl_dot > _cutoff) {
    emittance = _power * pow(dl_dot, _sharpness) / (
                          _attenuation.x +
                          _attenuation.y * distance +
                          _attenuation.z * _position.squared_distance(point));
  }
  else {
    emittance = color(0);
  }

  return lightSample(direction, emittance, distance);
}


/////////////////////
// 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;
}