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Department for Ecoinformatics, Biometrics and Forest Growth

Faculty of Forest Sciences and Forest Ecology
at the
University of Göttingen



Growth Grammar Interpreter

Check also the web pages concerning the recent development of the GROGRA / GroIMP project!

Description of the software

GROGRA is a tool for the interpretation of stochastic, sensitive growth grammars. These form an extended variant of L-systems (Lindenmayer systems), i.e. string rewriting systems with parallel replacement, associated with a "turtle" interpretation of the generated strings for the creation of 3D geometrical branching structures. The grammars have to be written into an ASCII file, following a syntax which is described in the manual. The start word, on which the replacement rules will be applied, and the number of replacement steps are specified interactively. From this information, GROGRA generates a time series of 3D structures, standing for developmental steps of plants, sets of plants or plant organs. There is also the possibility of object instancing, i.e. geometrical objects can be defined by a part of the grammar and used repeatedly in the form of differently scaled copies by another part of the grammar. Output is provided in graphical form (screen, PostScript file, HTML, DXF, PovRay or AMAP-formatted files alternatively) or in the form of ASCII tables containing specific information about the modelled structures.
GROGRA contains also several analysis algorithms to explore the structure of the generated, artificial trees and of real, measured trees. The latter can be reconstructed in the software from files containing topological and geometrical information in a special code (dtd format = digital tree data format). Simulated and reconstructed trees are thus accessible in the same data format and with the same analysis tools.
An important feature of GROGRA are specialized data interfaces, allowing a transfer of structural information to simulation models of microclimatic conditions, tree-internal water flow or other processes. There are also preliminary forms of interfaces with other software for plant modelling and architectural analysis: AMAPmod-MTG (Godin et al., CIRAD), LIGNUM (Perttunen et al., METLA). It is planned to implement further interfaces and data analysis tools; see our Projects.

Structure of the GROGRA software

Documentation and examples:

Here the GROGRA manual and documentation from 1994 can be downloaded:
[gzipped Postscript file, 971 KB] (unzipped: 10.54 MB)
The following text (which includes some examples) has an appendix containing updates for the manual:
[gzipped Postscript file, 451 KB] (unzipped: 9.39 MB)

Example pictures generated by GROGRA:
Young Norway spruce trees based on botanical measurements (and this is the corresponding L-system),
Old Norway spruce trees simulating those on the Solling F1 research area.

Here you can find the current Readme-file which lists the latest new features of the software.


The software was developed at the Department for Ecoinformatics, Biometrics and Forest Growth, primarily by Winfried Kurth. The first GROGRA version (1.0) was implemented in 1992 with the purpose of simulating crown architecture of spruce trees. It emerged from a preceding software for self-similar growth simulation. Milestones of the development were the implementation of the cubic discretization for interfacing with a radiation model (version 1.5, in June 1993), the extension to parametric L-systems and interpretive rules (2.0, November 1993), the XWindows version (February 1995), the implementation of the "movie" modus in the SGI version which was first presented on the CeBIT 1996, the introduction of shared objects (3.0, August 1997) and the MS-Windows version (March 1999).

Versions of the software

GROGRA exists in several variants for different platforms:

The basic functionality is identical in all versions. However, the SGI version contains some graphical options which are not implemented on the other platforms (interpolation between developmental steps, movie modus, growth curve display) and is hence the most powerful variant. The MS-DOS version is very limited in its memory and is therefore suitable only for very simple example grammars with few steps of growth.

Availability of the software

GROGRA is a scientific software which is still under development. It is FREE for all who are interested in the use of growth grammars or in modelling or describing plant architecture. You should contact Winfried Kurth (wk((at)) informatik.uni-goettingen.de) to receive the latest version and to get advice concerning the installation, together with example files suited to your specific demands.

Related software

Several tools have been developed in our Plant Modelling Group around GROGRA and are interfaced with it:


Projects of the Plant Modelling Group

Back to Plant Modelling Group Homepage


Last modifications: March 31, 2011