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/******************************************************************/
/* 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 <cassert>
#include "constants.h"
#include "areaLightsource.h"
//////////////////
// Constructors //
//////////////////
areaLightsource::areaLightsource(const color& power, const std::shared_ptr<const boundedPrimitive>& geometry, const vec3d& attenuation)
{
_power = power;
_geometry = geometry;
_attenuation = attenuation;
if(_geometry)
{
_center = _geometry->sample(0.5f, 0.5).position();
_area = _geometry->area();
}
}
/////////////
// Methods //
/////////////
lightSample areaLightsource::intensityAt(const vec3d& point) const
{
// use the 'center position' and emulate a point light source
vec3d direction = point - _center;
float distance = direction.length();
float attenuation = ((_attenuation[2]*distance + _attenuation[1])*distance + _attenuation[0]);
// Done.
return lightSample(direction, _power / attenuation, distance - 2.0f * EPSILON); // reduce distance to avoid self-intersection
}
lightSample areaLightsource::emittanceAt(const vec3d& point, float r1, float r2) const
{
if(!_geometry) return lightSample();
// sample surface
surfaceSample sample = _geometry->sample(r1, r2);
// direction
vec3d direction = point - sample.position();
float distance = direction.length();
// handle backside case
if(direction.dot(sample.normal()) < 0.0f) return lightSample();
// Done.
return lightSample(direction,
_power / (2.0f * PI * _area),
distance - 2.0f * EPSILON, // reduce distance to avoid self-intersection
sample.pdf(),
direction.dot( sample.normal() ) / distance);
}
color areaLightsource::_emittance(const intersectionPoint& ip) const
{
// check if back hit
// Note: ip.direction toward the intersection point
if(ip.normal().dot(ip.direction()) > 0.0f) return color();
// evaluate emittance (assume point lies on light source)
return _power / (2.0f * PI * _area);
}
/////////////////////
// Private Methods //
/////////////////////
void areaLightsource::_print(std::ostream& s) const
{
if(_geometry)
s << "Area Lightsource: power=" << _power << ", attenuation=" << _attenuation << ", area=" << _area << " centered at: " << _center;
else s << "Invalid Area Lightsource";
}
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