Digital Design of Nature (eBook)

Oliver Deussen graduated in 1996 at the Institut für Betriebs- und Dialogsysteme at the University of Karlsruhe, from 1996 until 2000 he was assistent at the Institut für Simulation und Graphik at the Otto-von-Guericke University of Magdeburg, from September 2000 until March 2003 he was professor for computer graphics and media design at Dresden University of Technology, since April 2003 he works at the University of Constance. Bernd Lintermann: born at 20. Feb. 1967 in Duesseldorf, Germany1986: Student of Computer Scinece at the University of Karlsruhe (TH) with focus on computer graphics.1996-2001: artist and scientist in residence at the ZKM Institut for Visual Media.Since 2002: Employee of the ZKM Institute for Visual Media.

Preface 5
Foreword 7
Contents 9
1 Computer-Generated Plants 13
1.1 Modeling of Virtual Landscapes 15
1.2 Rendering Issues 17
1.3 Applications 18
2 Plants 21
2.1 The Shoot Axis 23
2.2 Budding 25
2.3 Branching Types 26
2.4 Spatial Division 27
2.5 Tropisms 28
2.6 Architectural Analysis of Trees 29
2.7 Leaves 31
2.8 Geobotanical Description Methods 33
2.9 Description Methods for Vegetation 36
3 Some Mathematics 39
3.1 Geometrical and Topological Models 39
3.2 Branching Structures 40
3.3 Trees as Fractal Objects 42
3.4 Phyllotaxis 46
3.5 Description of Plant Populations 48
3.6 Developmental Models 50
4 Procedural Modeling 55
4.1 Cellular Automata 56
4.2 A First Continuous Model 57
4.3 Three-Dimensional Procedural Models 58
4.4 Regulation of the Branching Process 60
4.5 Generation Using Particle Systems 61
4.6 A Fractal Tree Model 61
4.7 Geometric Modeling 63
4.8 An Approach Based on Budding 64
4.9 A Combinatorial Approach 66
4.10 Tree Modeling Using Strands 68
4.11 Approximate Modeling 70
4.12 Growth in Voxels 70
4.13 Modeling of Phyllotaxis 71
4.14 Remaining Questions 73
5 Rule-Based Modeling 75
5.1 Rewriting Systems 76
5.2 Lindenmayer Systems 77
5.3 Branching Structures 79
5.4 Three-Dimensional Commands 80
5.5 Stochastic and Parameterized Systems 82
5.6 Context-Sensitive Systems 84
5.7 Modeling of Phyllotaxis 86
5.8 Animation of L-Systems 87
5.9 Interactions of Plants and the Environment 88
5.10 Use of Position Information 90
5.11 Iterated Function Systems 91
5.12 Object Instancing 94
5.13 CSG-Based Modeling 96
5.14 Categorizing the Methods 98
6 Rule-Based Object Production 101
6.1 Algorithmic Multiplication 102
6.2 Component Types 103
6.3 Combination of Components 109
6.4 Examples 110
6.5 Shape Modeling 113
6.6 Animation 116
6.7 Resume 118
7 Modeling Terrain 125
7.1 Brownian Motion 126
7.2 From Functions to Terrain 129
7.3 Erosion 130
7.4 Interaction with Fractal Terrain 135
8 Modeling Vegetation 137
8.1 Direct Speci.cation of Distributions 140
8.2 Simulation of a Plant Population 146
8.3 Simulation of a Plant Association 147
8.4 Reduction of the Geometric Data 148
8.5 Instancing of Plant Populations 152
8.6 Modeling of a Sample Scene 158
9 Rendering 161
9.1 Local Lighting Models 164
9.2 The Rendering Equation 165
9.3 Radiosity 166
9.4 Raytracing 167
9.5 Further Rendering Methods 168
9.6 Photorealistic Renditions of Leaves 169
9.7 Rendering Complex Scenes 174
9.8 Plant Images Using Raytracing 179
9.9 Plant Images Using Radiosity 182
9.10 When Do Computer Images Appear Real? 182
10 Level-of-Detail 193
10.1 LOD Methods for Smooth Surfaces 194
10.2 Static LOD Methods for Trees 195
10.3 Dynamic Point-Based Representation 198
10.4 Dynamic Polygonal Representation 200
10.5 Point- and Line-Based Rendering 203
11 Landscape Sketches 213
11.1 Nonphotorealistic Rendering 214
11.2 Traditional Drawings of Plants 218
11.3 Synthetic Plant Drawings 223
11.4 Rendering of Cross-Hatching 230
11.5 Resume 236
12 Media Art 239
12.1 William Latham 240
12.2 Karl Sims 243
12.3 Christa Sommerer and Laurent Mignonneau 251
12.4 Bill Viola, Tree of Knowledge 255
12.5 SonoMorphis 257
A Practical Plant Modeling 263
A.1 The Xfrog Modeling Environment 263
A.2 Modeling a Flower 265
A.3 Modeling a Tree 270
B Glossary 277
Figure credits 283
Bibliography 287
Index 299

11 Landscape Sketches (p. 201-202) 
Artistic Renditions 

                                                                                        

In contrast to photorealistic landscape images, the rendering of synthetic plant and landscape sketches has undergone little research so far. However, the already- addressed areas of application in architecture and landscaping require this kind of rendering. Currently, prefabricated images, which are combined via computer, most often must suffice. In addition, there are several collections of images [58] that incorporate lots of plant images in different styles and scales. These images can be copied and added to the drawings.

Aside from the enormous manual effort that is needed to combine the images, this method, of course, is only applicable for single images. New media, however, permit entirely new forms of presentation. The user should be able to analyze planned buildings virtually, to see them in different views, and to modify the corresponding scenes interactively. This is not possible using traditional plant images as part of a series. Digital plant models and drawings are required, which can be turned and moved and thereby reflect a spatial coherence. Since this kind of modeling is also useful in areas outside of architecture and landscaping, such as biology, botany and education, developing the proper methods and tools is a worthwhile undertaking that reaches far beyond the rendering of plants.

In this chapter we will introduce different approaches for the production of plant images in the style of hand-drawn artworks. After a short introduction into the area of nonphotorealistic rendering (NPR), traditional drawing styles used by artists will be examined with regard to their algorithmic implementation. It has become evident that some drawing styles are replicated satisfactorily via the computer, while others cannot be simulated. In a new method, some of the traditional techniques are imitated, and sample plants are produced in various drawing styles. Sample animations can be found on the accompanying website that prove that models generated in this way have the required spatial coherence, i.e., they can be turned and scaled without interfering flickering effects.

An important aspect when drawing trees is the rendering of the trunk and the branches. Here the methods differ from those used for the leaves, since we are dealing with a totally different form of geometry. In particular, the production of cross-hatchings on the trunk and branches is an interesting problem that is, however, partly solved by existing approaches.


11.1 Nonphotorealistic Rendering

Not only the production of synthetic plant sketches, but also the entire area of nonphotorealistic rendering will be continuously investigated during the years to come. The subject has been in discussion since the 1990s, and today the second phase in investigating the problems has been reached, with some notable attempts to systemize the area (see [215]) and to classify the related approaches.

Aside from the purely scientific interest, a starting point for the investigation of such representational forms is the realization that many illustrations in books and other traditional print media are not photographs, but rather abstract drawings, sketches, and illustrations [212]. This might be due to technical reasons such as low printing costs. Beyond the cost factor, illustrations seem to offer a better way for expressing the contents of certain kinds of complex pictures. As an example, let us imagine that a medical anatomy atlas consisted only of photos. It would not be very expressive, because photographs can for the most part only vaguely reflect the internal organs of the body and their relationships to each other. Here drawings serve the intent of such a highly specialized thematic much better, since they can represent the important picture content with a few lines. Strothotte et al. emphasized such advantages of illustrations in various articles [194, 213, 214].