

Department for Ecoinformatics, Biometrics and Forest Growth
Faculty of Forest Sciences and Forest Ecology
at the
University of Göttingen
PLANT MODELLING GROUP
GROGRA
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.
History
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:
- GL-based version for SGI workstations under Irix,
- XWindows-based version for Unix workstations (Sun, DEC Alpha,
IBM) and for Linux 7.0,
- MS-Windows version for Win95/98 or NT PC,
- a demo version for PCs under MS-DOS.
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:
- GROPARS (GROgra PARser), developed by Christian Neuse: A parser
checking the syntax of growth grammars much more thoroughly than
GROGRA itself and giving useful error messages if something is
wrong (currently running only on the PC),
- GroEdit (Grogra Editor), developed by Christian Neuse: A text
editor adapted to the manipulation of growth grammar files, offering
quick access to GROPARS (on the PC),
- GROBOL (GROwth of BOLe tool), developed by Dirk Lanwert: A software
for the graphical display, interpolation and animation of the shapes
of tree stems (for SGI workstations),
- GROFANT (GROgra Fractal ANalysis tool), developed by Stefan Luther:
A software for determining fractal dimensions with the box-counting
method (currently running on Sun workstations),
- GROCOM (GROwth grammar COMpound model), developed by Winfried Kurth
and Peter Schwendner: A software simulating carbon gain, allocation
and growth of a single tree, making use of radiation and allocation
models of other research groups and from the literature (Y. Knyazikhin,
R. Sievänen, J. Perttunen, A. Takenaka),
- GroIMP (GROGRA-related Interactive Modelling Platform), developed
by Ole Kniemeyer: An interactive tool for manipulating and visualizing
virtual plants, forest stands and other 3D objects and for combining
process-oriented and architectural models at several scales of resolution and
using a graph-grammar based language (XL). See
www.grogra.de. GroIMP is currently still
under development.
Projects of the Plant Modelling Group
Back to Plant Modelling Group Homepage
Last modifications: March 31, 2011