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A novel profile based model for virtual representation of quasi-symmetric plant organs

Mebatsion H.K., Boudon F., Godin C., Pradal C., Génard M., Goz-Bac C., Bertin N.. 2011. Computers and Electronics in Agriculture, 75 (1) : p. 113-124.

DOI: 10.1016/j.compag.2010.10.006

A novel modeling procedure for semi-symmetrical plant organs using longitudinal and transverse organ profiles was developed to simplify and improve virtual organ representation. Fruits were used as model organs. The fruits were divided into halves to capture the fruit profile. Using a regular photo camera (Nikon-Coolpix 4500), and an in-house image acquisition setup, the half fruit images were captured. In-house Matlab (The Mathworks, Natick, MA) based program was used to determine the boundaries of the digitized images. Based on the boundary points, and using Fourier series approximation, the image boundaries were defined mathematically. Fourier series approximation defines boundary shapes using the sum of sine and cosine terms. Based on the Fourier descriptors, which are coefficients of the Fourier series approximation, fruit contours were extracted. Surface construction algorithms based on smoothed contour boundaries were developed. Because of non-axis symmetricity of most fruits, and the presence of surface perturbations, for example, carpels in tomato fruits, models based on only longitudinal cross sections were not satisfactory. A complete fruit model was finally developed by combining the longitudinal cross section of half fruits and the transverse cross section of whole fruits. To our knowledge, this is the first realistic geometrical fruit model that captures the fruit shape complexities. Such a model may be useful to analyze the genetic and environmental controls of fruit morphological and biochemical properties. Our modeling approach has limitation in producing geometric models for unusual curved shape plant organs such as banana, cucumbers, cassava and Jerusalem artichoke that are not quasi-symmetrical along the longitudinal axis.

Mots-clés : fruits; modèle végétal

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