By default, DIVA instantiates each project with the default materials file, located in C:\DIVA\Daylight\material.rad. Project-specific materials can be defined in the .\ProjectName - DIVA\Resources\material.rad file. The ProjectName - DIVA directory is located in the same folder as your Rhino file. When the materials button is clicked, materials are always loaded from the project-specific material.rad file. The project-specific file can be overwritten with the default file by running the Location command.
Any Radiance material primitive can be defined in these files and selected for use in daylighting simulations.
There are several websites which document possible Radiance materials,
A Note of Caution
If a Radiance material primitive is incorrectly defined, the Radiance program oconv will fail, causing all DIVA simulations to fail. If your simulations suddenly do not work after adding a new material, check that it is defined appropriately in material.rad and re-run the Materials command.
Defining a Custom Metal Material
For example, to add a custom reflective metal material into DIVA, we can see from Radiance Materials Notes at Artifice that the 'Metal' primitive is defined as below, where specularity is typically greater than 0.9 and roughness is typically in a range from 0-0.2.
modifier metal material_name
5 red_reflectance green_reflectance blue_reflectance specularity roughness
void metal SimpleMetal_0.44
5 0.44 0.44 0.44 0.9 0.125
Defining a Custom Glass Material
For glass definitions, Radiance requires that the user translates transmission (Tn) to transmissivity (tn).
For instance if you wanted to define a glass material with a 65% transmission, the definition would be:
void glass Glass_Transmission_65
3 0.7085 0.7085 0.7085
Above, the R, G, and B transmissivity factors are derived from the transmission of the glass. For more information, see: http://radsite.lbl.gov/radiance/refer/ray.html#Materials.
For an easy way to convert transmission to transmissivity, you can use the Excel converter below.