this paper, such as the global distribution of radiative energy in the tree crowns, which affects the amount of light reaching the leaves and the local temperature of plant organs. The presented framework itself is also open to further research. To begin, the precise functional specification of the environment, implied by the design of the modeling framework, is suitable for a formal analysis of algorithms that capture various environmental processes. This analysis may highlight tradeoffs between time, memory, and communication complexity, and lead to programs matching the needs of the model to available system resources in an optimal manner. A deeper understanding of the spectrum of processes taking place in the environment may lead to the design of a mini-language for environment specification. Analogous to the language of L-systems for plant specification, this mini-language would simplify the modeling of various environments, relieving the modeler from the burden of low-level programming in a general-purpose language. Fleischer and Barr's work on the specification of environments supporting collisions and reaction-diffusion processes [20] is an inspiring step in this direction. Complexity issues are not limited to the environment, but also arise in plant models. They become particularly relevant as the scope of modeling increases from individual plants to groups of plants and, eventually, entire plant communities. This raises the problem of selecting the proper level of abstraction for designing plant models, including careful selection of physiological processes incorporated into the model and the spatial resolution of the resulting structures. The complexity of the modeling task can be also addressed at the level of system design, by assigning various components o...

Interaction with the environment is a key factor affecting the development of plants and plant ecosystems. In this paper we introduce a modeling framework that makes it possible to simulate and visualize a wide range of interactions at the level of plant architecture. This framework extends the formalism of Lindenmayer systems with constructs needed to model bi-directional information exchange between plants and their environment. We illustrate the proposed framework with models and simulations that capture the development of tree branches limited by collisions, the colonizing growth of clonal plants competing for space in favorable areas, the interaction between roots competing for water in the soil, and the competition within and between trees for access to light. Computer animation and visualization techniques make it possible to better understand the modeled processes and lead to realistic images of plants within their environmental context. CR categories: F.4.2 [Mathematical Logi...

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We review cellular automata as a modeling formalism and discuss how it can be used for modeling (spatial) ecological processes. The implications of this modeling paradigm for ecological observation are stressed. Finally we discuss some shortcom-ings of the cellular-automaton formalism and mention some extensions and generaliza-tions which may remedy these shortcomings. 1.

In these notes we survey applications of L-systems to the modeling of plants, with an emphasis on the results obtained since the comprehensive presentation of this area in The Algorithmic Beauty of Plants [61]. The new developments include: ffl a better understanding of theoretical issues pertinent to graphical applications of L-systems, ffl extensions to programming techniques based on L-systems, and ffl an extension of the range of phenomena expressible using L-systems. Keywords: L-system, fractal, plant, modeling, simulation, realistic image synthesis, emergence, artificial life. 1 Introduction In 1968, Aristid Lindenmayer introduced a formalism for simulating the development of multicellular organisms, subsequently named L-systems [36]. This formalism was closely related to abstract automata and formal languages, and attracted the immediate interest of theoretical computer scientists [67]. The vigorous development of the mathematical theory of L-systems [70, 27, 66] was follow...

: With the increase in computer performance, 3-dimensional simulations of tree architecture with an unprecedented level of detail became possible. A formal framework for such structural models is provided by parallel string rewriting grammars (Lindenmayer systems). This formalism is presented here, together with several extensions tailored for botanical and forestry applications, comprising interpretative rules, an accelerated expansion of string parts, and object references. These formalisms are demonstrated by models of growing beech shoots and spruce stands, having an empirical basis and made visible by a generic software named GROGRA. Keywords: tree architecture, virtual tree, crown morphology, crown development, Lindenmayer system, growth grammar, simulation, visualization Abstrakt: S rostouc'im v'ykonem poc'itac ffi u je tak'e umoznena 3-dimension'aln'i simulace stromov'e architektury s doposud nev'idan'ym stupnem jej'i komplexity. Form'aln'i technika pro tyto struktur'aln'i ...

Interaction with the environment is a key factor affecting the development of plants and plant ecosystems. In this paper we introduce a modeling framework that makes it possible to simulate and visualize a wide range of interactions at the level of plant architecture. This framework extends the formalism of Lindenmayer systems with constructs needed to model bi−directional information exchange between plants and their environment. We illustrate the proposed framework with models and simulations that capture the development of tree branches limited by collisions, the colonizing growth of clonal plants competing for space in favorable areas, the interaction between roots competing for water in the soil, and the competition within and between trees for access to light. Computer animation and visualization techniques make it possible to better understand the modeled processes and lead to realistic images of plants within their environmental context. Keywords: scientific visualization, realistic image synthesis, software design, L−system,

-- context-sensitive, 30 -- deterministic, 14 -- differential, 56 -- environmentally sensitive, 44 -- non-propagating, 25 -- parametric, 13, 44 -- propagating, 25 -- stochastic, 21 -- table, 44 -- with fragmentation, 28 leaf, 15 letter, 8 -- parametric, 9, 12 lineage, 29 model, 2 module, 3, 12 -- child, 4 -- parent, 4 nutation, 52 parameter, 9 -- actual, 12 Visual models of plant development 65 130. J. Weber and J. Penn. Creation and rendering of realistic trees. Proceedings of SIGGRAPH '95 (Los Angeles, California, August 6--11, 1995), pages 119--128, ACM SIGGRAPH, New York, 1995. 131. F. D. Whisler, B. Acock, D. N. Baker, R. E. Fye, H. F. Hodges, J. R. Lambert, H. E. Lemmon, J. M. McKinion, and V. R. Reddy. Crop simulation models in agronomic systems. Advances in Agronomy, 40:141--208, 1986. 132. B. F. Wilson. The growing tree. The University of Massachusetts Press, Amherst, 1984. 133. T. Yokomori. Stochastic characterizations of EOL languag