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The metal, metal2, metfunc and metdata materials are for opaque surfaces, where specular highlights are modified with the material color. A pattern modifying the metal material types will affect the material color.
Metal is the simplest metallic material type.
![[Metal Parameters Dialog]](images/metaldef.gif)
Color:
The color values will modify the diffusely and specularly
reflected light.
Values lower than [0.01 0.01 0.01] or higher than [0.95 0.95 0.95] are rare.
Specularity:
The fraction of incident light that is immediately
reflected in mirror like fashion.
Roughness:
Roughness is specified as the rms slope of surface facets.
A value of 0 corresponds to a perfectly smooth surface,
and a value of 1 would be a very rough surface. Roughness
values above 0.2 are unusual. The roughness affects only
the specular reflection.
Metal2 is similar to metal, but with anisotropic roughness. This means that specular highlights in the surface will appear elliptical rather than round.
![[Basic Metal2 Parameters Dialog]](images/metal2basicdef.gif)
Roughness u:
Roughness v:
The roughness is specified seperately along the direction
of the anisotropy (u) and along the direction on the surface
perpendicular to it (v). Both values can't be smaller
than 0.001. The highlight will be narrower in the direction
of the smaller roughness value.
The vector u is defined on the Procedural page of
the dialog.
![[Procdural Metal2 Parameters Dialog]](images/metal2procdef.gif)
Function File:
This pop-up list offers all function files known to the
system for selection.
If a file is active, then the
variables in that file can be selected for one or several
of the vector coordinates. Otherwise, the coordinates
must be entered as expressions.
Edit...
Start the text editor that was configured in the project
preferences to edit the function file.
New...
Create a new function file, and start the text editor
to edit it.
Direction Vector X/Y/Z:
The coordinates of the direction vector orienting the anisotropy
can either be selected from the variables in a function file
as selected above, or they may be entered as
expressions.
An expression can contain numeric values, operators
and all functions and variables known to the material.
If an expression is not valid, then the entry field
will have a red background, and the message bar at the
bottom of the dialog will show a diagnostic message.
The Transformation page
of the dialog can be used
to transform the vector, possibly to bring it in alignment
with the geometry of the surface the material modifies.
The metfunc material type is for opaque surfaces with arbitrary bidirectional reflectance distribution functions (BRDF) and has the same basic properties as metal, with the exception of roughness. Roughness isn't required here, since the BRDF specification is much more powerful.
![[Procdural Metfunc Parameters Dialog]](images/metfuncprocdef.gif)
Function File:
This pop-up list offers all function files known to the
system for selection.
Edit...
Start the text editor that was configured in the project
preferences to edit the function file.
New...
Create a new function file, and start the text editor
to edit it.
Reflection Function:
An arbitrary bidirectional reflectance
distribution function (BRDF) defined in the function file above.
The function takes four arguments,
the x, y and z direction towards the incident light and
the solid angle subtended by the source (which is supplied
to faciliate averaging, but is often ignored). Radiance
will also accept functions with less parameters.
The pop-up list offers all formally
valid functions from the function file for selection.
The selected function should integrate to 1 over the
projected hemisphere.
Real Arguments
Rayfront will check the selected function file to
decide how many real arguments the material definition
should supply. If this number is greater than the
mandatory arguments specifying the basic properties,
then the expected number of entry fields in the list
is made available. Supplying those arguments is
optional, but failing to do so may result in runtime
errors when the selected function relies on a specific
argument which is not set.
The Transformation page of the dialog can be used to transform the vector, possibly to bring it in alignment with the geometry of the surface the material modifies.
The metdata material type is used for arbitrary BRDFs that are most conveniently given as interpolated data and has the same basic properties as metal, with the exception of roughness. Roughness isn't required here, since the BRDF specification is much more powerful.
![[Procedural Metdata Parameters Dialog]](images/metdataprocdef.gif)
Function File:
This pop-up list offers all function files known to the
system for selection.
Edit...
Start the text editor that was configured in the project
preferences to edit the function file.
New...
Create a new function file, and start the text editor
to edit it.
BRTD Function:
An arbitrary bidirectional reflectance
distribution function. The function takes five arguments,
the interpolated data value,
the x, y and z direction towards the incident light and
the solid angle subtended by the source (which is supplied
to faciliate averaging, but is often ignored). Radiance
will also accept functions with less parameters.
The pop-up list will offer all formally
valid functions from the function file for selection.
The selected function should integrate to 1 over the
projected hemisphere.
Data File:
The file containing the reflectance data for interpolation.
Rayfront currently limits valid data to three dimensions.
Import...
This button invokes a file open dialog, and the selected
data file will then be imported into the project.
Index Functions:
One or several functions (depending on the number of dimensions
in the data file) to index into the data. The functions take
four arguments each, the x, y, and z coordinates of the
direction to the incident light and the solid angle
subtended by the light source. Functions with less arguments
are also valid.
Real Arguments
Rayfront will check the selected function file to
decide how many real arguments the material definition
should supply. If this number is greater than the
mandatory arguments specifying the basic properties,
then the right number of entry fields in the list
is made available. Supplying some or all of those arguments is
optional, but failing to do so may result in runtime
errors when the selected function relies on a certain
argument, and this argument is not specified.
The Transformation page of the dialog can be used to transform the vector, possibly to bring it in alignment with the geometry of the surface the material modifies.