Towards a 3D light model for growth chambers
using an experiment-assisted design
Michaël
1INRA
1
Chelle ,
Mustafa
1
Demirel ,
-UMR Environnement et Grandes Cultures
2
Christophe
2
Renaud
Laboratoire d'Informatique du Littoral (LIL)
78850 Thiverval-Grignon - France
BP 719 - 62228 Calais cedex - France
chelle@grignon.inra.fr
renaud@lil.univ-littoral.fr
Genomic studies
FSPM modeling
Analysis of various genotypes in the same environment
Isolating a gene for a given function without environment bias.
Plant organ response law to physical environment
Fine scale analysis of plant growth and development
Growth chamber experiments
Comparing plants grown in the same chamber
Comparing experiments in different growth chambers
Need of spatially homogenous growth conditions
Needs of “standardized” conditions between chambers
Yes, but what in the real world ?
Spatial variability of irradiance
What a diversity for growth chamber models
(Strader chamber, France)
How to bypass a “growth chamber” effect in ecophysiology due to spatial heterogeneity
Modeling the incident or absorbed light for each plant (or organ)
But there is two main difficulties:
Complexity of light sources
≈
High level of multiple scattering
Case of an empty Strader growth chamber
Measurement the spatial distribution of light
by distinguishing using black occultations
the 0, 1 and (2 to ∞) orders of scattering
Ray-tracing
on simple geometry of perfect mirror
Results for PAR worktable irradiance
E=E0(75%) + E1(18%) + Ex(7%)
Angular radiance distribution
measured
simulated
Directionality of light sources + glossy materials => choice of the light model
Test with Radiance (G. Ward)
radiosity
photon mapping (Ray Tracing)
A future OO photon mapping
for growth chamber lighting
Irradiance distribution in an empty room
Step 1
Trace a photon
within a light source
Principle of RT
Step 2
Follow the photon path within the room
until having bounced a wall n times or
hitting the foliage bounding box
What next?
The next steps are:
 implementing in Java or C++ this
new algorithm
 testing for contrasted growth
chamber types and cultures.
Conclusion
OK, but too slow!
Step 3
Follow the photon within
the plant bounding box
Simple experiments have enabled
us to quickly proposed a new light
model, well adapted to the growth
chamber case.