Module imp3d
Package de.grogra.imp3d.shading

Class Phong

java.lang.Object
de.grogra.graph.impl.Edge
de.grogra.graph.impl.Node
de.grogra.imp3d.shading.ChannelMapNode
de.grogra.imp3d.shading.ColorMapNode
de.grogra.imp3d.shading.Material
de.grogra.imp3d.shading.Phong
All Implemented Interfaces:
Icon, IconSource, Scattering, Shader, ChannelMap, ColorMap, Manageable, PersistenceCapable, Shareable, RenderedIcon, Scattering, Shader, UserFields, XObject, Map, Serializable
public class Phong extends Material
A Phong shader represents a Phong-like reflector. Its bidirectional reflection/transmission distribution functions are as follows:

At a given point x, let cd be the diffuse color (components R, G, B) at that point, α the alpha-component of the diffuse color and ct the transparency color. For each color component, set

cαt = 1 + α (ct - 1)
Let cs be the specular color and n the shininess exponent. Let r be the reflection coefficient as computed by Math2.fresnel(javax.vecmath.Vector3f, javax.vecmath.Vector3f, float, javax.vecmath.Vector3f, javax.vecmath.Vector3f).
  • Now if interpolatedTransparency is true, set
    kd = (1 - cαt) cd
    ks = (1 - cαt) cs + r cαt
    kt = (1 - r) cαt
  • Otherwise, set
    kd = cd
    ks = cs + r cαt
    kt = (1 - r) cαt
The bidirectional reflection distribution function is
BRDF(x, ωi, ωo) = kd / π + ks (n + 2) max(cos β, 0)n / 2π
where β is the angle between ωi and the direction of ideal reflection of ωo.

The bidirectional transmission distribution function is

BTDF(x, ωi, ωt) = kt (ηt / ηi)2 δω+ (ωi - T(ωt))
where η stands for the index of refraction, T for the direction of transmission according to Fresnel's formulas, and δω+ is the δ-distribution with respect to projected solid angle ω+.
Author:
Ole Kniemeyer
See Also:

  • Field Details

    • DEFAULT_DIFFUSE

      public static final ColorMap DEFAULT_DIFFUSE

    • DEFAULT_TRANSPARENCY

      public static final ColorMap DEFAULT_TRANSPARENCY

    • DEFAULT_SPECULAR

      public static final ColorMap DEFAULT_SPECULAR

    • DEFAULT_DIFFUSE_TRANSPARENCY

      public static final ColorMap DEFAULT_DIFFUSE_TRANSPARENCY

    • DEFAULT_AMBIENT

      public static final ColorMap DEFAULT_AMBIENT

    • DEFAULT_EMISSIVE

      public static final ColorMap DEFAULT_EMISSIVE

    • MAX_SHININESS

      public static final float MAX_SHININESS
      See Also:

    • DEFAULT_SHININESS

      public static final float DEFAULT_SHININESS
      See Also:

    • DEFAULT_TRANSPARENCY_SHININESS

      public static final float DEFAULT_TRANSPARENCY_SHININESS
      See Also:

    • $TYPE

      public static final Node.NType $TYPE

    • diffuse$FIELD

      public static final Node.NType.Field diffuse$FIELD

    • specular$FIELD

      public static final Node.NType.Field specular$FIELD

    • shininess$FIELD

      public static final Node.NType.Field shininess$FIELD

    • transparency$FIELD

      public static final Node.NType.Field transparency$FIELD

    • transparencyShininess$FIELD

      public static final Node.NType.Field transparencyShininess$FIELD

    • interpolatedTransparency$FIELD

      public static final Node.NType.Field interpolatedTransparency$FIELD

    • diffuseTransparency$FIELD

      public static final Node.NType.Field diffuseTransparency$FIELD

    • ambient$FIELD

      public static final Node.NType.Field ambient$FIELD

    • emissive$FIELD

      public static final Node.NType.Field emissive$FIELD

  • Constructor Details

    • Phong

      public Phong()

  • Method Details

    • createPhong

      public static Phong createPhong()

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

    • getFlags

      public int getFlags()

    • convertShininess

      public static float convertShininess(float x)

    • shade

      public void shade(Environment env, RayList rays, Vector3f out, Spectrum outSpec, Tuple3d outColor)
      Description copied from interface: Shader
      Computes color of outgoing light ray for given input. The computed value is, for each color component j = R, G, B, the following sum over all incident rays k:
      ∑k |cos θk| BSDFj(ωk, out) ck,j
      where BSDFj is the bidirectional scattering distribution function (= BRDF + BTDF) at the point env.point, ωk and ck the direction and color of ray k, and θk the angle between the surface normal and ωk.

      The computation may include physically invalid contributions, which may not fit into the formula above, e.g., ambient or emissive light contributions.

      Parameters:
      env - the environment for scattering
      rays - the incoming rays
      out - the direction unit vector of the outgoing ray (i.e., pointing away from the surface)
      outSpec - spectrum of outgoing ray
      outColor - the output color will be placed in here

    • computeMaxRays

      public void computeMaxRays(Environment env, Vector3f out, Spectrum outSpec, Ray reflected, Tuple3f refVariance, Ray transmitted, Tuple3f transVariance)
      Description copied from interface: Shader
      Computes, for the given input, the reflected and transmitted importance rays for which the reflection/transmission probability densities (integrated over the spectrum) attain a maximum. The reflection probability density (measured with respect to solid angle) for the outgoing importance direction (i.e., incoming light direction) ω, given a fixed incident direction in, is
      pr(ω) = cos θ BRDF(ω, in) / R
      where BRDF is the bidirectional reflectivity distribution function, θ the angle between the surface normal and ω, and R the total reflectivity for the incident direction, i.e., the integral over cos θ BRDF(ω, in). The transmission probability density is defined correspondingly.

      The color-fields are set to the total reflectivity/transparency for the incident direction for each color component R, G, B. Thus, for physically plausible BRDF/BTDF, the component-wise sum of reflected.color and transmitted.color lies in the interval [0, 1], and the difference to 1 is the amount absorbed.

      The color may be zero if there is no reflected or transmitted ray, respectively, i.e., if the surface is fully transparent, opaque, or absorbing. The origin-fields of the rays will never be set.

      The computed variances are defined to be, for each color component, (approximations for) the angular mean quadratic deviations of the densities from the returned maximal ray directions. E.g., for perfect reflection/transmission, these variances are zero, whereas for a perfect lambertian reflector, the variance of reflection is ∫ cos θ (1 / π) θ2 dω = (π2 - 4) / 8. This is the value of Shader.LAMBERTIAN_VARIANCE.

      The ray properties which are not mentioned are neither used nor modified. These are the origin and its density, and the direction density.

      Parameters:
      env - the environment for scattering
      out - the (negated) direction unit vector of the incoming ray (i.e., pointing away from the surface)
      outSpec - spectrum of incoming ray
      reflected - the reflected ray with maximal probability
      refVariance - the angular mean quadratic deviation from reflected
      transmitted - the transmitted ray with maximal probability
      transVariance - the angular mean quadratic deviation from transmitted

    • 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.

      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.

      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

    • isTransparent

      public boolean isTransparent()

    • main

      public static void main(String[] args)

    • clone

      public Phong clone()
      Overrides:
      clone in class Node

    • getNTypeImpl

      protected Node.NType getNTypeImpl()
      Description copied from class: Node
      This method returns the Node.NType which describes the managed fields of the class of this node. This method has to be implemented in every concrete subclass.
      Overrides:
      getNTypeImpl in class Node
      Returns:
      type describing the managed fields of the class of this node

    • newInstance

      protected Node newInstance()
      Description copied from class: Node
      This method returns a new instance of the class of this node. This method has to be implemented in every concrete subclass.
      Overrides:
      newInstance in class Node
      Returns:
      new instance of class of this node

    • isInterpolatedTransparency

      public boolean isInterpolatedTransparency()

    • setInterpolatedTransparency

      public void setInterpolatedTransparency(boolean value)

    • getDiffuse

      public ChannelMap getDiffuse()

    • setDiffuse

      public void setDiffuse(ChannelMap value)

    • getSpecular

      public ChannelMap getSpecular()

    • setSpecular

      public void setSpecular(ChannelMap value)

    • getShininess

      public ChannelMap getShininess()

    • setShininess

      public void setShininess(ChannelMap value)

    • getTransparency

      public ChannelMap getTransparency()

    • setTransparency

      public void setTransparency(ChannelMap value)

    • getTransparencyShininess

      public ChannelMap getTransparencyShininess()

    • setTransparencyShininess

      public void setTransparencyShininess(ChannelMap value)

    • getDiffuseTransparency

      public ChannelMap getDiffuseTransparency()

    • setDiffuseTransparency

      public void setDiffuseTransparency(ChannelMap value)

    • getAmbient

      public ChannelMap getAmbient()

    • setAmbient

      public void setAmbient(ChannelMap value)

    • getEmissive

      public ChannelMap getEmissive()

    • setEmissive

      public void setEmissive(ChannelMap value)

    • accept

      public void accept(ShaderVisitor visitor)

    • accept

      public void accept(ChannelMapNodeVisitor visitor)
      Overrides:
      accept in class ChannelMapNode