This document summarizes procedural methods for terrain modelling. It discusses generating height maps, erosion simulation, vegetation distribution, road networks, and urban environments like buildings procedurally. Current research focuses on integrated frameworks that generate more detailed and realistic virtual worlds in a controllable, intuitive manner. Procedural modelling is active area of research and aims to automate terrain creation to reduce time and costs compared to manual 3D modelling.

1. A Survey of
Procedural Methods for
Terrain Modelling
Ruben Smelik
Klaas Jan de Kraker
Saskia Groenewegen
Tim Tutenel
Rafael Bidarra

2. Motivation for Automated Terrain Modelling
• Game worlds are increasing in size, detail and visual realism
• Manual design requires effort, time, 3D modelling skills, money, etc.
Wolfenstein 3D (id, 1992) Crysis (Crytek, 2007)
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3. Procedural content generation
• Content generation procedures based on rules, random numbers, etc.
• Also know as data amplification algorithms:
• Few parameters => large amount of content
• Common techniques:
• Fractals
• Rewriting systems
• Simulations
• Advantages:
• Saves effort / time / money
• Variation through randomness
• Storage
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4. Current limitations
• Too random, user has no real control over outcome
• Trial and error
• In-depth knowledge and experimentation required
• Unintuitive parameters, e.g. “persistence”
• Methods have not (yet) been integrated properly
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5. Topics in Procedural Terrain Modelling
1. Earth (height-maps, eroded landscapes)
2. Water (oceans, rivers and lakes)
3. Vegetation (plant models, distribution)
4. Road (networks)
5. Urban (buildings, facades)
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6. Earth - Height-map Generation
• Subdivision
Miller, G. S. P. (1986)
The Definition and Rendering of Terrain Maps.
• Fractal Brownian Motion (using Perlin Noise)
Musgrave, F. K. (1993)
6 Methods for Realistic Landscape Imaging. Amsterdam,Tuesday, June 16 2009

7. Earth - Erosion Simulation
• Thermal erosion
Benes, B. and Forsbach, R. (2001)
Layered Data Representation for Visual Simulation of
Terrain Erosion.
• Fluvial erosion
Anh, N. H., Sourin, A., and Aswani, P.
(2007)
Physically based Hydraulic Erosion
Simulation on Graphics Processing Unit.
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8. Earth - Commercial Tools
TerraGen (Planetside Software)
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9. Water - Rivers, Oceans and Lakes
Belhadj, F. and Audibert, P. (2005)
Modeling Landscapes with Ridges and Rivers: Bottom Up Approach.
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10. Vegetation - Plant Models
• L-Systems (symbolic rewriting grammar)
Měch, R., Prusinkiewicz, P. (1994).
Visual models of plants interacting with their environment.
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11. Vegetation - Distribution Simulation
Realistic distribution of plants
based on an ecosystem model
Deussen, O., Hanrahan, P., Lintermann, B., Měch, R., Pharr, M., and Prusinkiewicz, P. (1998).
Realistic Modeling and Rendering of Plant Ecosystems.
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12. Vegetation - Commercial tools
SpeedTree (IDV, inc.)
XFrog (Greenworks)
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13. Road - Network Patterns
Sun, J., Yu, X., Baciu, G., and Green, M. (2002).
Template-based Generation of Road Networks for Virtual City Modeling.
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14. Road - Network Generation
• L-Systems with validity checks, slope constraints and population-
oriented rules
Parish, Y. I. H. and Müller, P. (2001).
Procedural Modeling of Cities.
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15. Urban - Building Grammars
• Split and Shape grammars
Müller, P., Wonka, P., Haegler, S., Ulmer, A., and Gool, L. V. (2006)
Wonka, P., Wimmer, M., Sillion, F., and Ribarsky, W. (2003)
Procedural Modeling of Buildings.
Instant Architecture.
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16. Urban - Commercial Tools
“Random” roads and city
Virtual Pompei
16 CityEngine (Procedural, inc.) Amsterdam,Tuesday, June 16 2009

17. Integrated Procedural Terrain Modelling
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18. Current Results
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19. Conclusions
• Procedural modelling is an active research area with many
developments
• Focus shifts from height-map generation to urban environments
• Research directions:
• Performance
• GPU programming
• More detailed urban environments
• E.g. building interiors
• Integrated frameworks with intuitive controls
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