Emitter Class Reference

Abstract representation of emittance defined at a single point on a surface in 3-space (describing a light). More...

#include <Emitter.h>

Inheritance diagram for Emitter:

List of all members.

Public Member Functions
Constructors
	Emitter (SurfacePoint &pt, Sampler *sampler=NULL, Material *parent=NULL)
virtual	~Emitter ()
Initialization
virtual void	init ()
	Performs any initialization that may be necessary before beginning to use this Emitter.
Main usage interface
virtual bool	isEmitter ()
virtual SpectralSampleSet	getLe (const Vector3 &wo)=0
virtual SpectralSampleSet	getPower ()
virtual SpectralSampleSet	getRadiantExitance ()
virtual SpectralSampleSet	getLe0 ()
virtual SpectralSampleSet	getLe1 (const Vector3 &wo)
virtual void	preview (Shape *shape)
	Sets up OpenGL material state (light properties) to enable a crude/fast preview of this light in OpenGL.
Sampling interface
virtual Event	sample ()
	Samples an exitent vector according to the underlying distribution of emitted radiance at the surface point.
virtual real_t	getPdf (const Event &event)
virtual SpectralSampleSet	getBSDF (const Vector3 &wi, const Vector3 &wo)
	Mimics the behavior of a BSDF by separating emittance, Le(x,wo), into two parts: Le0(x) and Le1(x,wo). Le0(x) is independent of 'wo' and represents the total radiant exitance emitted at point x. Le1(x,wo) represents Le(x,w) / Le0(x), or in words, the directional distribution of emitted radiance at x, corresponding to the fraction of emitted radiance in direction 'wo' with respect to the total radiant exitance emitted at point x.
Accessors/Mutators
SurfacePoint &	getSurfacePoint ()
Material *	getParent ()
Protected Attributes
SurfacePoint &	m_pt
Material *	m_parent
SpectralSampleSet	m_power
SpectralSampleSet	m_radiantExitance
Sampler *	m_sampler

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Detailed Description

Abstract representation of emittance defined at a single point on a surface in 3-space (describing a light).

Author:

Travis Fischer (fisch0920@gmail.com)

Matthew Jacobs (jacobs.mh@gmail.com)

Date:

Fall 2008

The reason Emitter subclasses BSDF is for convenience during generation and evaluation of paths in bidirectional path tracing. Emittance at a point in a given direction, Le(x,wo), is broken into two parts, Le0(x), and Le1(x), as originally detailed by Veach and Guibas (see Eric Veach's thesis, section 8.3.2). Scattering at a vertex can then be uniformly viewed as evaluation / sampling of a BSDF, including initial, fake 'scattering' at a light source, which can be viewed as a special case of scattering with no incident vector (the incident vector is thus disregarded).

See also:

Emitter::getBSDF() or the Path class for more details.

Definition at line 29 of file Emitter.h.

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Constructor & Destructor Documentation

Emitter::Emitter	(	SurfacePoint &	pt,
		Sampler *	sampler = NULL,
		Material *	parent = NULL
	)			[inline]

Definition at line 34 of file Emitter.h.

virtual Emitter::~Emitter

(

)

[inline, virtual]

Definition at line 39 of file Emitter.h.

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Member Function Documentation

void Emitter::init

(

)

[virtual]

Performs any initialization that may be necessary before beginning to use this Emitter.

Note:

default implementation initializes power from PropertyMap and calculates radiant exitance

Reimplemented from BSDF.

Reimplemented in EnvironmentMap, and NullEmitter.

Definition at line 33 of file Emitter.cpp.

bool Emitter::isEmitter

(

)

[virtual]

Returns:

true iff this Emitter emits energy (is a light source)

Note:

if 'isEmitter' returns false, 'getLe' and 'getPower' must return SpectralSampleSet::black

Definition at line 51 of file Emitter.cpp.

virtual SpectralSampleSet Emitter::getLe

(

const Vector3 &

wo

)

[pure virtual]

Returns:

the spectral radiance emitted along the given vector

Implemented in EnvironmentMap, NullEmitter, OmniEmitter, and OrientedEmitter.

SpectralSampleSet Emitter::getPower

(

)

[virtual]

Returns:

the spectral power of this Emitter, representing the total radiant energy emitted from surfaces associated with this Emitter (with units watts)

Note:

total Le emitted by integrating 'getLe' over the the sphere of exitant directions and over the surface of the underlying shape should equal the power of this emitter

Definition at line 55 of file Emitter.cpp.

SpectralSampleSet Emitter::getRadiantExitance

(

)

[virtual]

Returns:

the spectral radiant exitance (aka radiosity) of the surface containing this Emitter, where radiant exitance is defined as power per unit surface area (with units watts/m^2)

Definition at line 59 of file Emitter.cpp.

SpectralSampleSet Emitter::getLe0

(

)

[virtual]

Returns:

Le0(x,0) which represents the total radiant exitance at this point

Definition at line 63 of file Emitter.cpp.

SpectralSampleSet Emitter::getLe1

(

const Vector3 &

wo

)

[virtual]

Returns:

Le1(x,wo) which represents the directional distribution of radiant exitance in the given direction

Definition at line 67 of file Emitter.cpp.

void Emitter::preview

(

Shape *

shape

)

[virtual]

Sets up OpenGL material state (light properties) to enable a crude/fast preview of this light in OpenGL.

Note:

default implementation places a GL pointlight at the center of the bounding box of the given shape

Reimplemented from BSDF.

Reimplemented in EnvironmentMap, and NullEmitter.

Definition at line 71 of file Emitter.cpp.

Event Emitter::sample

(

)

[virtual]

Samples an exitent vector according to the underlying distribution of emitted radiance at the surface point.

Returns:

the sampled vector

Implements BSDF.

Definition at line 151 of file Emitter.cpp.

real_t Emitter::getPdf

(

const Event &

event

)

[virtual]

Returns:

the probability density of having sampled the given out out vector 'event' with respect to whatever underlying sampling strategy is being used to sample this Emitter

Implements BSDF.

Definition at line 160 of file Emitter.cpp.

SpectralSampleSet Emitter::getBSDF	(	const Vector3 &	wi,
		const Vector3 &	wo
	)			[virtual]

Mimics the behavior of a BSDF by separating emittance, Le(x,wo), into two parts: Le0(x) and Le1(x,wo). Le0(x) is independent of 'wo' and represents the total radiant exitance emitted at point x. Le1(x,wo) represents Le(x,w) / Le0(x), or in words, the directional distribution of emitted radiance at x, corresponding to the fraction of emitted radiance in direction 'wo' with respect to the total radiant exitance emitted at point x.

Returns:

the directional distribution of emitted radiance in direction 'wo'

Note:

all implementations should disregard 'wi', as it has no physical interpretation in the context of an Emitter

for details, see Eric Veach's thesis, section 8.3.2

Implements BSDF.

Definition at line 167 of file Emitter.cpp.

SurfacePoint& Emitter::getSurfacePoint

(

)

[inline]

Returns:

the SurfacePoint at which this Emitter instance is defined

Reimplemented from BSDF.

Definition at line 164 of file Emitter.h.

Material* Emitter::getParent

(

)

[inline]

Returns:

the parent Material which instantiated this Emitter

Note:

the parent Material is also a PropertyMap and contians all key-value inputs to this Emitter

Reimplemented from BSDF.

Definition at line 174 of file Emitter.h.

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Member Data Documentation

SurfacePoint& Emitter::m_pt [protected]

Reimplemented from BSDF.

Definition at line 182 of file Emitter.h.

Material* Emitter::m_parent [protected]

Reimplemented from BSDF.

Definition at line 183 of file Emitter.h.

SpectralSampleSet Emitter::m_power [protected]

Definition at line 186 of file Emitter.h.

SpectralSampleSet Emitter::m_radiantExitance [protected]

Definition at line 189 of file Emitter.h.

Sampler* Emitter::m_sampler [protected]

Definition at line 191 of file Emitter.h.

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The documentation for this class was generated from the following files:

• Emitter.h
• Emitter.cpp