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java.lang.Object de.grogra.persistence.ShareableBase de.grogra.imp3d.shading.SwitchShader
public abstract class SwitchShader
This abstract base class defines a shader which switches between a set of
actual shaders based on the shading environment and ray direction. This
can be used, e.g., to use different shaders for front and back side
(see the subclass SideSwitchShader
), or to use different shaders
depending on the algorithm (raytracer or light model).
Nested Class Summary  

static class 
SwitchShader.Type

Field Summary  

static SwitchShader.Type 
$TYPE

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

LAMBERTIAN_VARIANCE 
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  

SwitchShader()

Method Summary  

float 
computeBSDF(Environment env,
Vector3f in,
Spectrum specIn,
Vector3f out,
boolean adjoint,
Spectrum bsdf)
Evaluates bidirectional scattering distribution function for given input. 
void 
computeMaxRays(Environment env,
Vector3f in,
Spectrum specIn,
Ray reflected,
Tuple3f refVariance,
Ray transmitted,
Tuple3f transVariance)
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. 
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. 
protected abstract Shader 
getShaderFor(Environment env,
Vector3f in)
This method has to be implemented by subclasses and defines the actual shader which shall be used depending on the environment and the ray direction. 
boolean 
isTransparent()

void 
shade(Environment env,
RayList in,
Vector3f out,
Spectrum specOut,
Tuple3d color)
Computes color of outgoing light ray for given input. 
protected void 
transformEnvironment(Environment e)

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 
Methods inherited from interface de.grogra.imp3d.shading.Shader 

accept 
Methods inherited from interface de.grogra.ray.physics.Scattering 

getAverageColor, getFlags 
Methods inherited from interface de.grogra.persistence.Manageable 

getManageableType 
Field Detail 

public static final SwitchShader.Type $TYPE
Constructor Detail 

public SwitchShader()
Method Detail 

public float computeBSDF(Environment env, Vector3f in, Spectrum specIn, Vector3f out, boolean adjoint, Spectrum bsdf)
Scattering
The computed spectrum is an integral over the spectrum of the following product:
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}
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)
= L^{1}(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)
= W^{1}(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.
computeBSDF
in interface Scattering
env
 the environment for scatteringin
 the (negated) direction unit vector of the incoming ray
(i.e., pointing away from the surface)specIn
 the spectrum of the incoming rayout
 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
public void computeMaxRays(Environment env, Vector3f in, Spectrum specIn, Ray reflected, Tuple3f refVariance, Ray transmitted, Tuple3f transVariance)
Shader
in
, is
in
) / R
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 componentwise 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 originfields 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) θ^{2} dω
= (π^{2}  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.
computeMaxRays
in interface Shader
env
 the environment for scatteringin
 the (negated) direction unit vector of the incoming ray
(i.e., pointing away from the surface)specIn
 spectrum of incoming rayreflected
 the reflected ray with maximal probabilityrefVariance
 the angular mean quadratic deviation from reflected
transmitted
 the transmitted ray with maximal probabilitytransVariance
 the angular mean quadratic deviation from transmitted
public void generateRandomRays(Environment env, Vector3f out, Spectrum specOut, RayList rays, boolean adjoint, java.util.Random rnd)
Scattering
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)
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)
rays.size
). Then, for every
frequency ν the sum
out
, μ)
specOut
(μ) dμ dω
If this Scattering
instance is in fact a
Light
source, adjoint
is true
,
and the BSDF is defined as BSDF(out
, μ; ω, ν)
= L^{1}(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)
= W^{1}(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.
generateRandomRays
in interface Scattering
env
 the environment for scatteringout
 the direction unit vector of the outgoing ray
(i.e., pointing away from the surface)specOut
 the spectrum of the outgoing rayrays
 the rays to be generatedadjoint
 represents out
a light ray or an importance ray?rnd
 pseudorandom generatorScattering.computeBSDF(de.grogra.ray.physics.Environment, javax.vecmath.Vector3f, de.grogra.ray.physics.Spectrum, javax.vecmath.Vector3f, boolean, de.grogra.ray.physics.Spectrum)
protected abstract Shader getShaderFor(Environment env, Vector3f in)
env
 environment for which shading computations are to be performedin
 given ray direction
public boolean isTransparent()
isTransparent
in interface Shader
public void shade(Environment env, RayList in, Vector3f out, Spectrum specOut, Tuple3d color)
Shader
out
) c_{k,j}
env.point
,
ω_{k} and c_{k} the direction and color of ray k,
and θ_{k} the angle between the surface normal
and ω_{k}.
The computation may include physically invalid contributions, which may not fit into the formula above, e.g., ambient or emissive light contributions.
shade
in interface Shader
env
 the environment for scatteringin
 the incoming raysout
 the direction unit vector of the outgoing ray
(i.e., pointing away from the surface)specOut
 spectrum of outgoing raycolor
 the output color will be placed in hereprotected void transformEnvironment(Environment e)


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