Retro-reflecting materials


Is there a way to simulate the behavior of retro-reflecting materials? Even an approximation will do.

Thanks in advance!

Hi “Tmux”(?), there are several ways to achieve that:

  1. Describe the BRDF in terms of the cal-language. Radiance comes with an example for glass beads ( in the lib).

  2. Model the underyling geometry and compute the BRDF using genBSDF. This was shown at the Radiance Workshop in Padua:
    Grobe, De Michele, & Papaiz (2016). Research of the modeling and measuring of solar shadings with very peculiar behavior. 15th International Radiance Workshop, Padua, Italy.

  3. Get the BRDF measured and compile it into a data-driven reflection model as demonstated in Grobe (2018). Characterization and data-driven modeling of a retro-reflective coating in Radiance. Energy and Buildings, 162, pp. 121-133.

Best, Lars.

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There is also a fourth option, which is to feed a retroreflective function to bsdf2ttree or bsdf2klems, either of which will accept a .cal file as input.


Thanks for your suggestions!

I’m unable to locate the “” file, is it only included in some release version onwards?


It should be included with the supplementary and auxiliary files available towards the bottom at the official release page.

We are looking into incorporating this in CVS or by some other means to make sure everyone gets it in future.