htrdr‑materialsmaterials list format

A htrdr‑materials file lists materials in plain text. Each line of the file gives the name of the material. For opaque materials, the material name is followed by the path to a file storing the spectral properties of the associated Bidirectional Reflectance Distribution Function (BRDF), saved in mrumtl(5) format. The material temperature is defined as the last parameter in the line, after the BRDF file mentioned above.

The material name can be composed of any character except spaces and tabs. The path to the mrumtl(5) file must be a valid absolute path in the file system.

Text after the # character is considered a comment and is therefore ignored, as are empty lines.

The file format is as follows:

htrdr-materials ::= material
material ::= name⟩ ⟨properties
properties ::= |brdf⟩ ⟨temperature
brdf ::= path # mrumtl file
temperature ::= real # In Kelvin

The following file lists 3 materials. The first, grass, has its spectral BRDF defined in file A001.mrumtl. The second, named sand, has its spectral properties recorded in file B002.mrumtl. Both materials have a temperature of 300 Kelvin. The final material is a semi-transparent material named air with no additional properties defined in this file:

grass   /opt/materials/A001.mrumtl 300
sand    /opt/materials/B002.mrumtl 300
air     none


The htrdr‑materials format was first developed for the htrdr(1) program.

October 5, 2023 UNIX