Measured materials (opaque)
Measured materials (opaque)
Embedded Files
Opaque materials are defined by the way they reflect light depending on the direction of observation, and the direction and wavelength of the light arriving on the material. This behaviour can be characterized by a function called BRDF (Bidirectional Reflectance Distribution Function). The BRDF can be measured and it can be simulated in Predict Engine.
Examples of specular measured materials
Predict Matter supports different types of measured BRDF, identified by the tool used to measure them :
Seelab and Murakami
Seelab and Murakami
Seelab and Murakami BRDFs are stored in one single *.csv file. The file contains the measure of the material in the plane of incidence : the corresponding Input Type is "Plane".
Next to the measure file, a preview of the measure is displayed in the interface. This preview gives you information on the content of the measure :
The measure is displayed in the reflection hemisphere,
The curves represent the intensity of the light reflected by the material for different wavelengths and different light directions : in the example here against all 3 measures contain 2 lobes (one a 0° and one at 45°),
The light directions are represented by yellow lines in the hemisphere,
When the measure contains data in a very large range, you can display the curves using a log scale.
The curves can be interpreted as follow :
When the intensity of the curves at different wavelengths varies a lot, the color of the curves with the higher intensity gives a good idea of the resulting color of the material : in the example here against, the top curve represents a blue plastic,
Most materials reflect light mainly in the specular direction : the direction that mirrors the incident light. The curves of such materials form a lobe around the specular direction, the thinner the lobe the shinier the material will be : in the example here against, the top curve is a plastic (the lobe is very large), the middle curve is a brushed metal (the lobe is quite thin), and the bottom curve is a shiny metal (the lobe is very thin).
Material defined with a blue plastic measurement
Material defined with a brushed metal measurement
Material defined with a shiny metal measurement
Measured BRDFs are big sets of datas and can be heavy on the memory, the “Quality” factor given on the material for Plane and Hemispherical measures enables you to reduce the size (and quality) of a material.
NB : this quality factor has a huge influence on the memory space used by the measure when rendering.
Eldim
Eldim
Eldim BRDFs are stored in several *.dat files. Each file contains the hemispherical measure of one lobe : the measure of the material at a given incident light direction given by its azimuth and its inclination. The corresponding Input Type is "Hemisphere".
Measured BRDFs are big sets of datas and can be heavy on the memory, the “Quality” factor given on the material for Plane and Hemispherical measures enables you to reduce the size (and quality) of a material. A quality of 1 is the original material quality. A quality of 0 is the minimum quality supported by Predict Matter to still be able to simulate the measure.
X-Rite AxF SVBRDF
X-Rite AxF SVBRDF
Predict Engine can simulate materials stored in X-Rite material format AxF (Appearance eXchange Format). These materials are representations of measured complex materials such as textured surfaces for instance.
Examples of AxF materials
You can define an AxF material in different ways :
Use the Predict Matter shader or the Predict Matter material edition window to link the *.axf file to the Predict Matter material,
If you are using the HDRP pipeline, use the Unity HDRP AxF shader,
If you have a Unity industrial license and the AxF Importer Package, use *.axf files directly as materials on your geometries. The AxF file will be automatically used in Predict Matter as well.
You can create à Unity material automatically from a *.axf file by right-clicking on a *.axf file in the Project tab and selecting the menu "PredictSuite - Matter/Generate AxF Material".
You can export the content of a *.axf file (textures + log) by right-clicking on a *.axf file in the Project tab and selecting the menu "PredictSuite - Matter/Export AxF Datas".
Supported features :
The *.axf file stores a representation of the measured material. At the moment, Predictive Matter only supports the following representations : SVBRDF Ward (Version 1) , SVBRDF GGX (Version 1) and CarPaint2 (Version 1).
AxF materials can be represented with spectral datas. At the moment, Predict Matter does not support spectral AxF materials with the SVBRDF Ward representation. You can still use spectral AxF materials, but their RGB representation will be used instead.
When an AxF material is defined with RGB and spectral datas, you can choose which representation is used in Predictive Matter. When using the RGB representation, the algorithm used to convert the RGB representation into a spectral representation in Predictive Matter will be either [Smits, 1999] for SVBRDF materials or the AxF internal conversion algorithm for CarPaints materials.
AxF materials can optionally include a clear coat (a thin layer of dielectric material, like polish for instance). At the moment, Predict Matter does not support clear coats on SVBRDF AxF materials : for these materials, the clear coat will be ignored.
Predict Matter supports the CarPaint2 representation of AxF materials but these materials should be defined using a Car Paint shader. See the Car paint section for more details.
Like all other Predict Matter materials, AxF materials can have a normal map. In most AxF materials, normals are already included in the AxF file. If you add manually a normal map on an AxF material, the normal map contained in the AxF file will be ignored in Predict Matter.
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