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fbartolic / volcano

Mapping the surface of Jupiter's moon Io from one-dimensional time-series data.
MIT License
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More sophisticated reflected light models #7

Closed fbartolic closed 4 years ago

fbartolic commented 4 years ago

A group which models mutual occultations between Galilean satellites for the purpose of improving astrometric positions of the satellites uses a reflectance law which is more sophisticated than Lambert's cosine law. Here's a quote from a recent paper:

We successfully solved these issues by adopting a generalisation of Lambert scattering law given by Oren and Nayar (1994). The Oren-Nayer model takes into account the direction of radiance and the roughness of the surface in a natural way, so that the reflectance depends only of the albedo and in one more parameter that very smoothly tunes a wide range of surface roughness, and most importantly, regardless of the wavelength. This model realistically reproduces the illumination of an object in modern computer graphic scenes for movies and for the full Moon. (Oren and Nayar, 1994). In Dias-Oliveira et al. (2013) a simplified version of the model was used. Here, we implemented the complete version in Oren and Nayar (1994), taking into account the direct illumination and all inter-reflection components of the radiance.

They don't really describe how they implemented this in that paper but Dias-Oliveira et al. (2013) goes into more details. The relevant equations are 2-9 and A6, A7. The reflected intensity depends on the vector of incident and reflected light light which they get from JPL Horizons. Not sure if these integrals can be computed analytically.

fbartolic commented 4 years ago

Rodrigo implemented the Oren-Nayar model in the latest version of Starry and it works great.