Visualisation of the impact of complex fenestration systems (CFS) based on Radiance

illustration geronimo

Authors : J. Kaempf, C. Basurto, J.-L. Scartezzini

Last program version: 2016
[Download software] [Download manual]


GERONIMO is a user-friendly software for architects and lighting designers conceived to perform daylighting calculations. It allows visualizing the impact of Complex Fenestration Systems (CFS) in office buildings for different sky types (overcast and clear skies). The rendering engine of GERONIMO is the backward ray-tracing software RADIANCE. GERONIMO avoids the classical command-line usage of Radiance offering the use of a simple interface, which can be adapted to the users skills. The current version of the software can be downloaded free of charge.

Target public

Professionals of the building construction sector, such as architects and lighting designers familiar with computer design tools


The main purpose of GERONIMO is to facilitate the implementation of Complex Fenestration Systems (CFS), as part of daylighting strategies in buildings. This is at present a difficult task for architects and lighting designers, given the complexity of simulating the daylight flux propagation through a CFS and to the unavailability of simple tools to perform such tasks.
CFS are of special interest nowadays; they are based on the common principles of an efficient collection of the daylight flux, the blocking of sun rays and the spreading of the daylight flux on the work plane. They improve the light distribution in the room, while removing the potential excess of solar heat gains and contribute in that way to a displacement of electric lighting and a reduction of the fossil fuels demand [1].
The light transmission properties of CFS are measured using bidirectional goniophotometers, which were developed to characterize the bidirectional transmission distribution function (BTDF) of Complex Fenestration Systems [1].
The bidirectional transmission properties of a CFS (BTDF data) indicate how much and in what direction the daylight flux is redirected by the device [1]. GERONIMO facilitates the implementation of CFS in architectural projects by allowing the simulation of the daylight flux distribution by the CFS in a room using the corresponding BTDF Data in a virtual model.

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Screen shots


Photometric characteristics (BTDF Data) of mirrored venetian blinds measured using a CCD image based bidirectional goniophotometer



J.H. Kämpf, J.-L. Scartezzini, Ray-Tracing Simulation of Complex Fenestration Systems Based on Digitally Processed BTDF Data, Proc. of International Conference CISBAT 2011, Lausanne 14-16 September 2011 [download pdf]

J. Kämpf, J.-L. Scartezzini, GERONIMO: the CFS Daylighting Wizard, Paper presented at 4th Velux Daylight Symposium, Lausanne, 2011 [download pdf]

This version of the Geronimo Software can be downloaded free of charge.
->  Download (program version: V1.1 – 2016), manual in pdf format

What’s new in 1.1:

  • Setting view point, view direction and scale
  • Support for Window XML files

The software is also integrated in Relux Suite (Pro).

Computer: PC