Table Of Content

Exploring 3D visualisation of vegetation Joël Hempenius 2 Exploring 3D visualisation of vegetation Joël Hempenius Exploring 3D visualisation of vegetation Author: Joël Hempenius Supervisor: dr.ir. R.J.A. van Lammeren Technical supervisor: ing. H. Kramer Date: 19 Februari 2010 3 Exploring 3D visualisation of vegetation Joël Hempenius 4 Exploring 3D visualisation of vegetation Joël Hempenius Abstract 3D visualisation of vegetation change can communicate for instance the loss of rare plant species, vegetation stress or vegetation risks in order to raise awareness. 3D visualisation might also be helpful in the nature management process, by visualising the effects of certain decisions, such as removing biomass from a vegetation area. In order to make a 3D visualisation of a vegetation model, it is necessary that this model has a map as output together with more information which describes the composition of this vegetation. These will serve as the input for distribution modelling of the individual plant species. 3D models of the plants can be placed at the point distribution which is created by this distribution tool. To get these 3D models of the plants, the plants which contribute to the grain, colour and structure of the vegetation type will have to be selected and 3D modelled. This point distribution of the plants and the 3D models can be brought together in a 3D simulation, together with a DEM and an aerial photo to model height and to give the substrate a natural colour There are several models for vegetation modelling, plant distribution modelling and 3D plant modelling. The vegetation modelling is done using vegetation mapping models or vegetation succession models. The mapping can be done using geostatistical interpolation, generalized linear networks, artificial neural networks and classification trees. These models result in a map, and in order to be used as input for the plant distribution tool, a description of the abundance of each plant species within the vegetation types is necessary. However, when the species abundance is described using the Braun-Blanquet scales as a cover percentage, it is not possible to use it as input for a computer generated distribution, because this requires the plants per square meter as an input. A conversion is possible, but requires accurate modelled 3D plant models. The vegetation succession modelling models the transition from the one vegetation type to another vegetation type. This change is driven by changing circumstances for the plants and the output as biomass is calculated for five different layers in the vegetation. In order to model this layered output correctly, it is necessary that the 3D plant models give a correct representation of the biomass of the plants and it therefore requires accurate 3D growth models of the plant species. There methodologies for creating a plant distribution vary a lot in complexity: the complex Agent Based Models and Cellular Automata can model competition for resources and dispersion, but also require a lot of research, calibration and validation. A simple computer generated distribution on the other side does only require the number of plants per square meter per vegetation type as input. The 3D plant models can be divided into two types: the accurate models and the sketch based models. Accurate modelling techniques are AMAP and L-systems and it requires scientific measurements of the plants growth, size and shape to model a plant in 3D and the modelling needs to be calibrated and validated. These accurate 3D models are necessary to model vegetation succession or to make a conversion from a cover percentage to the number of plants per square metre. The accurate modelling techniques can also be used sketch based, but for instance Xfrog works faster if a plant has to be 3D modelled. Photographs from different angles of the plant can serve as the input for the sketch based modelling process. 5 Exploring 3D visualisation of vegetation Joël Hempenius This research has shown that 3D visualising a vegetation map with a computer generated distribution and sketch based 3D plant models is possible. However, vegetation maps with the plant species abundance described as cover percentage are unsuitable for 3D visualisation, unless an easy method is developed to convert this percentage to the number of plants per square meter. 6 Exploring 3D visualisation of vegetation Joël Hempenius Acknowledgements First, I would like to thank Ron van Lammeren for his supervision and advice on my thesis. I would like to thank Henk Kramer as technical supervisor for his ideas and advice on possible software solutions. I would like to thank Han van Dobben and Rik Huiskes for testing the 3D visualisation and for their comments and remarks about this visualization. Thanks to all the people who contributed to Virtual Terrain Project. It is great software and you proved that open source software can be a contribution to society! I would especially like to thank Ben Discoe for fixing the 3Dconnexion Spacenavigator support for Windows x64. And off course, I would like to thank Siegrit for all the support she has given me the past half year. 7 Exploring 3D visualisation of vegetation Joël Hempenius 8 Exploring 3D visualisation of vegetation Joël Hempenius Table of contents Abstract .......................................................................................................................... 5 Acknowledgements ........................................................................................................ 7 Table of contents ............................................................................................................ 9 1 Introduction ........................................................................................................... 15 1.1 Necessary models for a 3D visualisation ..................................................... 15 1.2 Distribution models ...................................................................................... 18 1.3 3 Dimensional plant growth models ............................................................ 19 1.4 Ameland case study ..................................................................................... 20 1.5 Problem description ..................................................................................... 20 1.6 Research objectives and research questions ................................................ 20 1.7 Methodology ................................................................................................ 21 1.7.1 Research introduction and research proposal .......................................... 21 1.7.2 Literature research ................................................................................... 21 1.7.3 Case study ................................................................................................ 21 1.7.4 Expert test ................................................................................................ 22 1.7.5 Finishing of the thesis .............................................................................. 23 1.8 Scope ............................................................................................................ 24 1.9 The structure of this thesis ........................................................................... 24 2 Vegetation modelling ............................................................................................ 25 2.1 Vegetation mapping models ........................................................................ 25 2.2 Vegetation succession modelling ................................................................. 27 2.3 What should be 3D visualised of these models? .......................................... 28 2.4 Conclusions on vegetation modelling .......................................................... 29 9 Exploring 3D visualisation of vegetation Joël Hempenius 3 Plant distribution models ....................................................................................... 31 3.1 Agent based modelling ................................................................................ 31 3.2 Cellular automata ......................................................................................... 32 3.3 Self thinning distributions ............................................................................ 33 3.4 L-systems distributions ................................................................................ 33 3.5 Computer generated distributions ................................................................ 34 3.6 Conclusions on distribution modelling ........................................................ 34 4 3D growth models and 3D plant models ............................................................... 35 4.1 L-Systems .................................................................................................... 35 4.2 AMAP .......................................................................................................... 38 4.3 Sketch based plant models ........................................................................... 39 4.4 Conclusions on 3D plant models ................................................................. 40 5 Data quality of vegetation maps ............................................................................ 41 5.1 Generalisation in the vegetation maps ......................................................... 41 5.2 Fuzzy boundaries ......................................................................................... 41 5.3 Completeness ............................................................................................... 42 5.4 Error propagation ......................................................................................... 43 5.5 Using raster vegetation maps ....................................................................... 43 5.6 Conclusions on the data quality of input vegetation maps .......................... 45 6 The Ameland case study ....................................................................................... 47 6.1 The input vegetation data ............................................................................. 49 6.2 The 3D plant models .................................................................................... 53 6.2.1 VisuAlea/PlantGL 3D plants written in L-systems ................................. 53 6.2.2 Xfrog 3D plants ........................................................................................ 56 10