htrdr 0.9.2

mrumtl(5)

NAME

mrumtl - ModRadUrb MaTeriaL file format

DESCRIPTION

mrumtl is a text file format that describes a Bidirectional Reflectance Distribution Function (BRDF) whose type and parameters can vary spectrally. Its data are described for a set of wavelengths or spectral bands that must be listed in ascending order.

Characters behind the hash mark (#) are considered comments and are therefore ignored, as well as empty lines, i.e. lines without any characters or composed only of spaces and tabs.

GRAMMAR

<mrumtl>            ::= <per-wlen-BRDF>
                      | <per-band-BRDF>

---

<per-wlen-BRDF>     ::= wavelengths <wavelengths-count>
                        <wlen-BRDF>
                      [ <wlen-BRDF> ... ]

<wlen-BRDF>         ::= <wavelength> <BRDF>
<wavelengths-count> ::= INTEGER
<wavelength>        ::= REAL # in nanometer

---

<per-band-BRDF>     ::= bands <bands-count>
                        <band-BRDF>
                      [ <band-BRDF> ... ]

<band-BRDF>         ::= <wavelength-min> <wavelength-max> <BRDF>

<bands-count>       ::= INTEGER
<wavelength-min>    ::= REAL # Inclusive bound in nanometers
<wavelength-max>    ::= REAL # Inclusive bound in nanometers

---

<BRDF>              ::= <BRDF-lambertian>
                      | <BRDF-specular>

<BRDF-lambertian>   ::= lambertian <reflectivity>
<BRDF-specular>     ::= specular <reflectivity>
<reflectivity>      ::= REAL # In [0, 1]

EXAMPLES

Describe a material with only two bands: one for the visible part of the spectrum and one for the long waves. In both cases use a diffuse reflectivity:

bands 2
380  780     lambertian  0.9 # Visible part
1000 100000  lambertian  0.1 # Infrared

Setup a material for a list of 17 wavelengths. This material is diffuse in short waves and specular in long waves:

wavelengths 17

# Short waves
430     lambertian  5.2e-2
450     lambertian  6.2e-2
500     lambertian  6.5e-002
600     lambertian  0.165
750     lambertian  0.175

# Long waves
1100    specular    0.1
1300    specular    0.17
1400    specular    0.1
2000    specular    0.1
2100    specular    0.4
2300    specular    0.18
2500    specular    0.9
2600    specular    0.95
2900    specular    0.4
3000    specular    0.3
4000    specular    0.0
100000  specular    0.0