de.grogra.imp3d.objects
Class SpectralLight

java.lang.Object
  de.grogra.persistence.ShareableBase
      de.grogra.imp3d.objects.SpectralLight

All Implemented Interfaces:

Manageable, Shareable, Emitter, Light, Scattering

public class SpectralLight
extends ShareableBase
implements Light

Nested Class Summary

static class

SpectralLight.Type

Field Summary

static SpectralLight.Type	$TYPE
static SCOType.Field	light$FIELD
static SCOType.Field	power$FIELD
static SCOType.Field	spectrum$FIELD

Fields inherited from interface de.grogra.ray.physics.Light

AMBIENT, AREA, DIRECTIONAL, NO_LIGHT, POINT, SKY

Fields inherited from interface de.grogra.ray.physics.Scattering

DELTA_FACTOR, IS_NON_OPAQUE, MIN_UNUSED_FLAG, NEEDS_NORMAL, NEEDS_POINT, NEEDS_TANGENTS, NEEDS_TRANSFORMATION, NEEDS_UV, RANDOM_RAYS_GENERATE_ORIGINS

Constructor Summary

SpectralLight()
spectral light constructor

SpectralLight(SpectralCurve curve)
spectral light constructor

Method Summary

void	accept(LightVisitor visitor)
double	completeRay(Environment env, Point3d vertex, Ray out)
float	computeBSDF(Environment env, Vector3f in, Spectrum specIn, Vector3f out, boolean adjoint, Spectrum bsdf) Evaluates bidirectional scattering distribution function for given input.
double	computeExitance(Environment env, Spectrum exitance) Evaluates the exitance function for given input.
void	generateRandomOrigins(Environment env, RayList out, java.util.Random random) Pseudorandomly generates, for the given input, a set of origins for this emitter.
void	generateRandomRays(Environment env, Vector3f out, Spectrum specOut, RayList rays, boolean adjoint, java.util.Random random) Pseudorandomly generates, for the given input, a set of scattered rays.
int	getAverageColor() Returns an average color for the scattering entity.
int	getFlags()
Light	getLight()
int	getLightType() Determines the type of light source which is represented by this light.
ManageableType	getManageableType()
float	getPower()
SpectralLightMap	getSpectrum()
double	getTotalPower(Environment env) Computes the total power of this light source which is emitted to the region defined by env.bounds.
boolean	isIgnoredWhenHit() Determines whether the light source shall be ignored when a shot ray happens to hit the geometry of the light source.
boolean	isShadowless() Determines whether the light source casts shadows or not.
void	setLight(Light light) Sets the directional emission distribution of the spectal light.
void	setPower(float value)
void	setSpectrum(SpectralCurve curve) sets the spectral distribution
void	setSpectrum(SpectralLightMap value)

Methods inherited from class de.grogra.persistence.ShareableBase

addReference, appendReferencesTo, fieldModified, getProvider, getStamp, initProvider, manageableReadResolve, manageableWriteReplace, removeReference

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

$TYPE

public static final SpectralLight.Type $TYPE

light$FIELD

public static final SCOType.Field light$FIELD

power$FIELD

public static final SCOType.Field power$FIELD

spectrum$FIELD

public static final SCOType.Field spectrum$FIELD

Constructor Detail

SpectralLight

public SpectralLight()

spectral light constructor

SpectralLight

public SpectralLight(SpectralCurve curve)

spectral light constructor

Parameters:

curve - the spectral curve, used by the lightsouce

Method Detail

accept

public void accept(LightVisitor visitor)

completeRay

public double completeRay(Environment env,
                          Point3d vertex,
                          Ray out)

Specified by:

completeRay in interface Emitter

computeBSDF

public float computeBSDF(Environment env,
                         Vector3f in,
                         Spectrum specIn,
                         Vector3f out,
                         boolean adjoint,
                         Spectrum bsdf)

Description copied from interface: Scattering

Evaluates bidirectional scattering distribution function for given input.

The computed spectrum is an integral over the spectrum of the following product:

|cos θ| BSDF(ω_i, ν_i; ω_o, ν_o) where BSDF is the bidirectional scattering distribution function (= BRDF + BTDF) at the point env.point, ω_i the (negated) direction of the incoming light ray, ν_i the frequency where the incoming ray is sampled, ω_o the direction of the outgoing light ray, ν_o the frequency where the outgoing ray is sampled, and θ the angle between the surface normal and out.

If adjoint is false, in and out describe true light rays from light sources to sensors. In this case, ω_i = in, ω_o = out, and the integral is

bsdf(ν) = |cos θ| ∫ BSDF(in, ν_i; out, ν) specIn(ν_i) dν_i Otherwise, adjoint is true. in and out then describe importance rays (inverse light rays from sensors to light sources). In this case, ω_i = out, ω_o = in, and the integral is bsdf(ν) = |cos θ| ∫ BSDF(out, ν; in, ν_o) specIn(ν_o) dν_o

If this Scattering instance is in fact a Light source, adjoint is false, and the BSDF is defined as BSDF(in, μ; ω, ν) = L¹(ω, ν) δ(μ - ν), i.e., the directional distribution of the emitted radiance at env.point, see Emitter. In this case, in is not used.

If this Scattering instance is in fact a Sensor, adjoint is true, and the BSDF is defined as BSDF(ω, ν; in, μ) = W¹(ω, ν) δ(μ - ν), i.e., the directional distribution of the emitted importance at env.point, see Emitter. In this case, in is not used.

The computation should be physically valid. This excludes, e.g., ambient or emissive light contributions.

The returned value is the value of the probability density p_ω that would be calculated by Scattering.generateRandomRays(de.grogra.ray.physics.Environment, javax.vecmath.Vector3f, de.grogra.ray.physics.Spectrum, de.grogra.ray.util.RayList, boolean, java.util.Random) if the ray happened to be one of the randomly generated rays.

Specified by:

computeBSDF in interface Scattering

Parameters:

env - the environment for scattering

in - the (negated) direction unit vector of the incoming ray (i.e., pointing away from the surface)

specIn - the spectrum of the incoming ray

out - the direction unit vector of the outgoing ray (i.e., pointing away from the surface)

adjoint - light ray or importance ray?

bsdf - the computed spectrum of the outgoing ray will be placed in here

Returns:

the value of the probability density for the ray direction

computeExitance

public double computeExitance(Environment env,
                              Spectrum exitance)

Description copied from interface: Emitter

Evaluates the exitance function for given input. The computed value is the spectrum of the radiant exitance (emitted power per area) L⁰_j(x, ν) at the point env.point in case of light sources, or the corresponding function W⁰_j(x, ν) in case of sensors.

The returned value is the value of the probability density p_x that would be calculated by Emitter.generateRandomOrigins(de.grogra.ray.physics.Environment, de.grogra.ray.util.RayList, java.util.Random) if env.point happened to be one of the randomly generated origins.

Specified by:

computeExitance in interface Emitter

Parameters:

env - the environment for scattering

exitance - the exitance values will be placed in here

Returns:

the value of the probability density for the ray origin

generateRandomOrigins

public void generateRandomOrigins(Environment env,
                                  RayList out,
                                  java.util.Random random)

Description copied from interface: Emitter

Pseudorandomly generates, for the given input, a set of origins for this emitter. They are generated such that they can be used for Monte Carlo-based photon tracing algorithms in the following way.

At first, we consider the case where the emitter is in fact a light source. Let L(x, ω, ν) be the emitted spectral radiance for the frequency ν at the light's surface point x in direction ω. The radiant exitance (emitted spectral power per area) at x is defined as

L⁰(x, ν) = ∫ cos θ L(x, ω, ν) dω where θ is the angle between the surface normal and ω. Now the directional distribution of the emitted radiance at x can be described by the density L¹(x, ω, ν) = L(x, ω, ν) / L⁰(x, ν) so that the radiance is split into L(x, ω, ν) = L⁰(x, ν) L¹(x, ω, ν) Let o_i and s_i denote the origins and spectra of the N generated rays (N = rays.size). Then for a function f(x, ν) which is to be integrated over the light surface, the sum 1 / N ∑_i s_i(ν) f(o_i, ν) is an unbiased estimate for the integral ∫ L⁰(x, ν) f(x, ν) dA The integral ranges over the whole surface A of the light source. As a consequence, the spectrum of a ray is to be considered as the ray's radiant spectral power.

Now if the emitter is a sensor, let W(x, ω, ν) be the emitted spectral importance for frequency ν at the sensors's surface point x in direction ω. The quantities W⁰(x, ν) and W¹(x, ω, ν) are defined similarly to the case of light sources:

W⁰(x, ν) = ∫ cos θ W(x, ω, ν) dω
W(x, ω, ν) = W⁰(x) W¹(x, ω, ν) The formulas for light sources are valid for sensors if the L-quantites are replaced by the corresponding W-quantities.

Let p_x be the probability density used for the ray origin, then the field originDensity is set to p_x(o_i) for each ray. For emitters which are concentrated at a single point (e.g., point lights) p_x is not a regular function, the value originDensity will be set to a multiple of Scattering.DELTA_FACTOR.

The ray properties which are not mentioned in the given formulas are neither used nor modified. These are the direction and its density.

Specified by:

generateRandomOrigins in interface Emitter

Parameters:

env - the environment

out - the outgoing rays to be generated

random - pseudorandom generator

generateRandomRays

public void generateRandomRays(Environment env,
                               Vector3f out,
                               Spectrum specOut,
                               RayList rays,
                               boolean adjoint,
                               java.util.Random random)

Description copied from interface: Scattering

Pseudorandomly generates, for the given input, a set of scattered rays. The scattered rays are generated such that they can be used for a Monte Carlo integration of a function f(ω;ν) over cos θ BSDF(ω_i, ν_i; ω_o, ν_o) in the following way:

• If adjoint is false, out = ω_o describes the direction of an outgoing light ray. In this case, the integration is with respect to ω_i. Let g(ω, ν; out, μ) = BSDF(ω, ν; out, μ)
• Otherwise, adjoint is true. In this case, out = ω_i describes the direction of an outgoing importance ray (an inverse light ray). Now the integration is with respect to ω_o. Let g(ω, ν; out, μ) = BSDF(out, μ; ω, ν)

Let d_i and s_i denote the directions and spectra of the N generated rays (N = rays.size). Then, for every frequency ν the sum 1 / N ∑_i s_i(ν) f(d_i; ν) is an unbiased estimate for the integral ∫ cos θ f(ω; ν) g(ω, ν; out, μ) specOut(μ) dμ dω θ is the angle between the surface normal and ω. The domain of integration is the whole sphere, since the bidirectional scattering distribution includes both reflection and transmission (BSDF = BRDF + BTDF).

If this Scattering instance is in fact a Light source, adjoint is true, and the BSDF is defined as BSDF(out, μ; ω, ν) = L¹(ω, ν) δ(μ - ν), i.e., the directional distribution of the emitted radiance at env.point, see Emitter. In this case, out is not used.

If this Scattering instance is in fact a Sensor, adjoint is false, and the BSDF is defined as BSDF(ω, ν; out, μ) = W¹(ω, ν) δ(μ - ν), i.e., the directional distribution of the emitted importance at env.point, see Emitter. In this case, out is not used.

Let p_ω be the probability density used for the ray direction (measured with respect to solid angle ω), then the field directionDensity of the ray i is set to p_ω(d_i). For ideal specular reflection or transmission, or for directional lights or sensors, p_ω is not a regular function, the value directionDensity will be set to a multiple of Scattering.DELTA_FACTOR.

The ray properties which are not mentioned in the given formulas are neither used nor modified. These are the origin and its density.

Specified by:

generateRandomRays in interface Scattering

Parameters:

env - the environment for scattering

out - the direction unit vector of the outgoing ray (i.e., pointing away from the surface)

specOut - the spectrum of the outgoing ray

rays - the rays to be generated

adjoint - represents out a light ray or an importance ray?

random - pseudorandom generator

See Also:

Scattering.computeBSDF(de.grogra.ray.physics.Environment, javax.vecmath.Vector3f, de.grogra.ray.physics.Spectrum, javax.vecmath.Vector3f, boolean, de.grogra.ray.physics.Spectrum)

getAverageColor

public int getAverageColor()

Description copied from interface: Scattering

Returns an average color for the scattering entity. This color is used for simplified graphical representations of the corresponding objects.

Specified by:

getAverageColor in interface Scattering

Returns:

an average color in Java's default sRGB color space, encoded as an int (0xAARRGGBB).

getFlags

public int getFlags()

Specified by:

getFlags in interface Scattering

getLight

public Light getLight()

getLightType

public int getLightType()

Description copied from interface: Light

Determines the type of light source which is represented by this light.

Specified by:

getLightType in interface Light

Returns:

one of Light.NO_LIGHT, Light.POINT, Light.AREA, Light.DIRECTIONAL, Light.SKY, Light.AMBIENT.

getManageableType

public ManageableType getManageableType()

Specified by:

getManageableType in interface Manageable

getPower

public float getPower()

getSpectrum

public SpectralLightMap getSpectrum()

getTotalPower

public double getTotalPower(Environment env)

Description copied from interface: Light

Computes the total power of this light source which is emitted to the region defined by env.bounds. Note that the computed value is not necessarily exact: It should be used just as a hint, e.g., when one of a set of lights has to be chosen randomly on the basis of their relative power.

Specified by:

getTotalPower in interface Light

Parameters:

env - environment which defines the bounds of the scene

Returns:

total power emitted to the region env.bounds

isIgnoredWhenHit

public boolean isIgnoredWhenHit()

Description copied from interface: Light

Determines whether the light source shall be ignored when a shot ray happens to hit the geometry of the light source.

Specified by:

isIgnoredWhenHit in interface Light

Returns:

true iff the light source shall be ignored

isShadowless

public boolean isShadowless()

Description copied from interface: Light

Determines whether the light source casts shadows or not.

Specified by:

isShadowless in interface Light

Returns:

true iff the light source does not cast shadows

setLight

public void setLight(Light light)

Sets the directional emission distribution of the spectal light. The directional emission distribution of the input lights is used as emission distribution

Parameters:

light - input light

setPower

public void setPower(float value)

setSpectrum

public void setSpectrum(SpectralCurve curve)

sets the spectral distribution

Parameters:

curve - is the spectral distribution

setSpectrum

public void setSpectrum(SpectralLightMap value)