PROF-LCPC
Photometric Rendering of Fog



Purpose
PROF-LCPC is a program which computes global illumination in a fog (or any other scattering medium). It aims at simulating luminance measurements in the field of vision of a driver (or any other observer).



Theory

PROF-LCPC uses a Monte-Carlo based light-tracing technique. The energy emitted by the light sources which illuminate the scene is decomposed into elements called "photons". The path of each photon is built by sampling the probability density functions associated with the photometric properties of the sources, the surfaces and the medium. Shadow rays are sent to the sensors along the path, to build radiance images.

PROF-LCPC was validated, first in simple geometries with analytic solutions, and then by comparison with measurements in artificial fog.

In the present version, PROF-LCPC is limited by the following hypotheses:

• homogeneous medium;
• analytic reflection models (Lambert, Phong);
• far-field photometry;
• no daylight.

The main advantage of PROF-LCPC lies in its ability to take into account the measured instensity distributions of the light sources and the scattering medium. It also takes multiple scattering into account.

The main drawback lies in the noise which is inherent to the Monte Carlo method. As a result, significant results can only be achieved after large computation times (several hours).



Implementation

PROF-LCPC was developped in C language. It is therefore portable, and was successfully compiled on various platforms (Windows, Linux and Irix). The software interface is in English as well as the technical documentation.

The user runs PROF-LCPC by means of a command line in a shell, with arguments and options. Input data is contained inside a single ASCII input file, which describes every geometric and photometric parameters of the simulation: the 3D scene, the light sources, the fog and the sensors.

The resulting radiance images are stored in floating point format inside binary files, in a simple format inspired by the PBM (Portable BitMap) standard.


Contact - Distribution

PROF-LCPC will be distributed freely to anyone who asks Eric Dumont and specifies a platform (PC with Windows or Linux, or SGI).

We will do our best to help users who report problems, without warranty nor liability whatsoever.