3D-Model Synthesis from 2D Partial Information:
a Natural Plant Application
Dr. Luis Da Costa
Ecole de Technologie Sup´erieure
Date: Monday November 27, 2006
Time: 12:20 p.m. - 1:10 p.m.
Location: 367 Votey
Abstract
The analysis of cultivated fields using near remote sensing has been demonstrated as the best method for detecting physiological disorders of the plants in the field. To perform this type of analysis it is important to be able to manipulate the plants virtually using computer models faithfully representing them; in this thesis, a method is proposed (from the definition of a formalism, to the design and test of an algorithm) for generating the models from field 2D photographs. The formalism chosen as the base for plants representation is called Lindenmayer Systems (LSystems); LSystems are grammatical systems controlled by an initial condition and one or more rewriting rules, and the repetitive iteration of an LSystem often produces interesting emergent behavior. However, it is difficult to discover the rules that produce a specific desired behavior in this formalism; this problem is called the ''inverse'' problem for Lindenmayer systems. Generating a computer model of a plant is equivalent to solving the inverse problem for a special subtype of this formalism, called ''bracketed Lindenmayer systems''; this paper demonstrates the possibility of solving the inverse problem for bracketed L-Systems by means of an evolutionary algorithm. A detailed description of the algorithm, along with the justification of the chosen design, are presented; a set of experiments, intended to test the correctness of the method, show that the algorithm explores in a satisfactory manner the space of candidate solutions, and that the approximations it proposes are adequate in most cases. Its limitations and weaknesses are also reported; we discuss them and outline our future work.