Module imp3d
Package de.grogra.imp3d.objects

Class DirectionalLight

java.lang.Object
de.grogra.persistence.ShareableBase
de.grogra.imp3d.objects.LightBase
de.grogra.imp3d.objects.DirectionalLight
All Implemented Interfaces:
Raytraceable, Light, Scattering, 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

  • Field Details

  • Constructor Details

    • DirectionalLight

      public DirectionalLight()

  • Method Details

    • getManageableType

      public ManageableType getManageableType()
      Specified by:
      getManageableType in interface Manageable

    • getPowerDensity

      public float getPowerDensity()

    • setPowerDensity

      public void setPowerDensity(float value)

    • 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.

    • draw

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

    • 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

    • generateRandomOrigins

      public void generateRandomOrigins(Environment env, RayList out, 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

    • 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

    • generateRandomRays

      public void generateRandomRays(Environment env, Vector3f out, Spectrum specOut, RayList rays, boolean adjoint, 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:
      • If adjoint is false, out = ωo describes the direction of an outgoing light ray. In this case, the integration is with respect to ωi. Let g(ω, ν; out, μ) = BSDF(ω, ν; out, μ)
      • Otherwise, adjoint is true. In this case, out = ωi describes the direction of an outgoing importance ray (an inverse light ray). Now the integration is with respect to ωo. Let g(ω, ν; out, μ) = BSDF(out, μ; ω, ν)
      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:

    • 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) specIn(νi) 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) specIn(νo) 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

    • createRaytracerLeaf

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

    • accept

      public void accept(LightVisitor visitor)
      Specified by:
      accept in interface Light