de.grogra.imp3d.objects
Class DirectionalLight

java.lang.Object
  extended by de.grogra.persistence.ShareableBase
      extended by de.grogra.imp3d.objects.LightBase
          extended by de.grogra.imp3d.objects.DirectionalLight
All Implemented Interfaces:
Raytraceable, Manageable, Shareable, Emitter, Light, Scattering
Direct Known Subclasses:
SunSkyToDirectionalLightWrapper

public class DirectionalLight
extends LightBase
implements Raytraceable

This class implements a directional light. Light rays are cast in the positive direction of the local z-axis.

Author:
Ole Kniemeyer

Nested Class Summary
static class DirectionalLight.Type
           
 
Field Summary
static DirectionalLight.Type $TYPE
           
static SCOType.Field powerDensity$FIELD
           
 
Fields inherited from class de.grogra.imp3d.objects.LightBase
color$FIELD, shadowless$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
DirectionalLight()
           
 
Method Summary
 void accept(LightVisitor visitor)
           
 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.
 RaytracerLeaf createRaytracerLeaf(java.lang.Object object, boolean asNode, long pathId, GraphState gs)
           
protected  void draw(Tuple3f color, RenderState rs)
           
 void generateRandomOrigins(Environment env, RayList out, java.util.Random rnd)
          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 rnd)
          Pseudorandomly generates, for the given input, a set of scattered rays.
 int getLightType()
          Determines the type of light source which is represented by this light.
 ManageableType getManageableType()
           
 float getPowerDensity()
           
 double getTotalPower(Environment env)
          Computes the total power of this light source which is emitted to the region defined by env.bounds.
 void setPowerDensity(float value)
           
 
Methods inherited from class de.grogra.imp3d.objects.LightBase
completeRay, getAverageColor, getColor, getFlags, isIgnoredWhenHit, isShadowless, setShadowless
 
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 DirectionalLight.Type $TYPE

powerDensity$FIELD

public static final SCOType.Field powerDensity$FIELD
Constructor Detail

DirectionalLight

public DirectionalLight()
Method Detail

accept

public void accept(LightVisitor visitor)

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(ωi, νi; ωo, νo)
where BSDF is the bidirectional scattering distribution function (= BRDF + BTDF) at the point env.point, ωi the (negated) direction of the incoming light ray, νi the frequency where the incoming ray is sampled, ωo the direction of the outgoing light ray, νo 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, ωi = in, ωo = out, and the integral is

bsdf(ν) = |cos θ| ∫ BSDF(in, νi; out, ν) specIni) dνi
Otherwise, adjoint is true. in and out then describe importance rays (inverse light rays from sensors to light sources). In this case, ωi = out, ωo = in, and the integral is
bsdf(ν) = |cos θ| ∫ BSDF(out, ν; in, νo) specIno) dνo

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 pω 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) L0j(x, ν) at the point env.point in case of light sources, or the corresponding function W0j(x, ν) in case of sensors.

The returned value is the value of the probability density px 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

createRaytracerLeaf

public RaytracerLeaf createRaytracerLeaf(java.lang.Object object,
                                         boolean asNode,
                                         long pathId,
                                         GraphState gs)
Specified by:
createRaytracerLeaf in interface Raytraceable

draw

protected void draw(Tuple3f color,
                    RenderState rs)
Overrides:
draw in class LightBase

generateRandomOrigins

public void generateRandomOrigins(Environment env,
                                  RayList out,
                                  java.util.Random rnd)
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 oi and si 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 si(ν) f(oi, 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 px be the probability density used for the ray origin, then the field originDensity is set to px(oi) for each ray. For emitters which are concentrated at a single point (e.g., point lights) px 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
rnd - pseudorandom generator

generateRandomRays

public void generateRandomRays(Environment env,
                               Vector3f out,
                               Spectrum specOut,
                               RayList rays,
                               boolean adjoint,
                               java.util.Random rnd)
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(ωi, νi; ωo, νo) in the following way: Let di and si denote the directions and spectra of the N generated rays (N = rays.size). Then, for every frequency ν the sum
1 / N ∑i si(ν) f(di; 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 pω 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 pω(di). For ideal specular reflection or transmission, or for directional lights or sensors, pω 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?
rnd - 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)

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

getPowerDensity

public float getPowerDensity()

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

setPowerDensity

public void setPowerDensity(float value)