1. Wall Grammar for Building Generation
Mathieu Larive and Véronique Gaildrat
Visual Objects, from Reality To EXpression
http://www.irit.fr/-Equipe-VORTEX
Oktal Synthetic Environment
http://www.oktal-se.fr
1/22

2. Contents
• Introduction
• Frontage Templates
• Groundwork and Roof Templates
• Results and Discussions
• Conclusion and Future Work
2/22

3. Problem
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4. Goals
• Quickly create a plausible (geo-typic) city around an already
modelized zone (geo-specific)
• Reach a level of detail satisfactory enough for a navigation
at ground level:
– modeling of the buildings’inside
– geometric modeling of the urban furniture
→ usage of automatic techniques inside AGETIM
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5. Generation steps
• Hierarchical division of
city generation process in
seven steps [Larive2005]
• Each step can be seen as a
logical LoD
5/22

6. Contents
• Introduction
• Frontage Templates
• Groundwork and Roof Templates
• Results and Discussions
• Conclusion and Future Work
6/22

7. Frontage Templates
• A frontage template contains a primary wall and possibly a
background material
• A frontage template can be seen as a style sheet that
describes:
– wall rendering
– possible dimensions and kinds of windows and doors
(described as textures or 3D objects)
– how to place these elements on the building
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8. Frontage Templates
• Formal grammar representation [Wonka2003]
• 2,5 dimensions paramatric wall grammar
Repetition rules Position rules
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9. Frontage Templates
• Wall Panel
– the unique terminal
symbol of our grammar
– various parameters:
• texture
– Background
– Decoration
• 3D object
• possible dimensions
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10. Frontage Templates
• Bordered Wall • Extruded Wall
– four margins – depth (positive or not)
– resize policy – depth faces generation
– BW → W boolean
– EW → W
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11. Frontage Templates
• Wall Grid
– Contains an unique
child wall
– Repetition
• Vertical
• Horizontal
• Both
– Controlled by two
cardinality intervals
– WG → Wnm
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12. Frontage Templates
• Wall List
– Several child walls
– Orientation (exclusive)
• Vertical
• Horizontal
– WL → W1W2...Wn
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13. Frontage Templates
• The combination of those different walls in a tree-like
hierarchy allows the user to build simple or complex
frontage templates
• Use of repetition schemes on every part of our
frontages (wall grid)
• Usage of previously generated 3D objects (such as
balconies or cornices)
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14. Frontage Templates
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15. Contents
• Introduction
• Frontage Templates
• Groundwork and Roof Templates
• Results and Discussions
• Conclusion and Future Work
15/22

16. Groundwork and Roof Templates
• Groundwork templates
– Z-min
– Z-max
– Extruded
Z-min Z-max Extruded
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17. Groundwork and Roofs Template
• Roof templates
– Based on the Straight
Skeleton method
[Felkel1998]
– One, two or four slopes
– Overhang (4 types)
– Currently, 10 various
roof types
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18. Contents
• Introduction
• Frontage Templates
• Groundwork and Roof Templates
• Results and Discussions
• Conclusion and Future Work
18/22

19. Results
• Various buildings on one building footprint
94 faces 350 faces 5600 faces
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20. Results
• Large scale urban area
17 362 buildings, 920 182 faces generated in less than 8 mn 20/22

21. Conclusion
• Able to generate buildings on any kind of footprint
– convex, non-convex, non-plane, even with holes
• Generated buildings are valid
– geometrically (no hole, no overlapping face, no empty
frontage -blind frontages-)
– no window or door on a frontage edge
• Once a building template is finished and robust, it can
be immediately reused (ready-to-use building template
library)
• Control of the geometric complexity, according to the
user hints
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22. Future Work
• Finalize the building
template editor
• Usage of the Urban Land
Use Model
– Road network generation
– Creation of lots and
building footprints
• Integration of all the
various generation steps
inside the same process
22/22