fokus k3d 2010

1Focus K3D Conference

Sophia Antipolis, 11-12 Feb. 2010

The architectonic-style likelihood principle for

procedural development of

Cultural Heritage Virtual Worlds

ELIOS Lab

F. Bellotti, R. Berta, S. Cardona, A. De Gloria

ELIOS Lab DIBE – University of Genoa



3D urban areas

3D reconstruction of a urban area for educational cultural Virtual Worlds (VWs) or Serious Games (SGs)A trade-off between the 3D model’s realism and weight

An impressive and culturally valid experiencePhotorealistic models, weather effects, surround-sound

audio, graspable virtual objects, natural lighting system

Performance and usability problems for an SG/VW online platformAn enjoyable experience and real-time interactive

exploration



3D model details

In a highly interactive system details are not fundamental

However, in Cultural Heritage, the player is acting almost like an art detective.

Highly realistic, complex systems are costly to implement

3D modeling and texturingTaking and processing pictures (ground-level images)



Travel in Europe

Involve students and teachers in living compelling adventures in a cultural SG

Easy configuration through authoring toolsEnhance the educational value also through content-creation

The artistic heritage domain involves strict requirements in terms of realism and cultural soundness

Feeling the “sense of place” for a compelling and fruitful experience

A cognitive foundationAfter a visit, a visitor typically remembers the general

features of a city, its architectonic styles.



Travel in Europe styles



The Architectonic Style Area algorithm

Procedural generation of buildings for VWs/SGs based on the concept of “architectonic likelihood”

Give players the sense of being in a particular city/areaNot to implement a detailed reconstruction of every single

building, but to single out few meaningful styles– the templates out of which the single buildings can be instantiated through

statistical variations

An architecture ontology, a statistic description of the architectonic elements

Outputs: facades for all the buildings in the area

Modeler responsibility shiftFrom the 3D implementation and image texturing – to the

definition of the architectural elements and their statistical description



Putting it all together

Geo-referencedGround elevated from a local 3D vectorial mapPrecise placement ensures compatibility/portability to

GISs and expansibility of the system

Few Point-Of-Interests (POIs)Rigorous reconstruction at a high level of detail

Culturally meaningful buildingsCathedrals, theaters, and outstanding palaces.

Textures for other palaces built by the ASA, a statistical template-basedalgorithm



Related work

A shape grammar with production rules that iteratively evolve a design by creating more and more details

Our approach is not concerned on generating the 3D shape of the buildings, but focuses on the look of the façade exploiting architectural grammars



Related works

Mueller subdivide a facade texture in a top-down manner into elements such as floors, tiles, windows, and doors

Image analysis to build semantic 3D models by detecting repetitions in the high-level facade structure

SketchaworldProcedural automatic reconstruction of environments based on semantics



ASA approach

A different point of view:identifying building templates in an area

focus on:facades rather than shapesautomation on the generation of instances by assembling

components based on a statistical description

Inline with educational aims of SGEmpowerment of users for an easy generation of content

Not exploit semantics to build 3D models from images, but use architectural knowledge to prepare semantic rich 2D textures



ASA steps

The Map: a 2D vectorial file (Autodesk AutoCAD 2004 DWG format)

3D generated by extruding the DWG polylines that represent the buildings

Height, roof shapes andfaçades textures aredetermined and appliedas results of thesubsequent steps of thealgorithm



Definition of the building Templates (Styles)

Define the building templates in the areaE.g. various types of palaces, villas, churches with their frequency

The algorithm will instantiate buildings in the area out of these frequency values.

ExampleGlass Skyscrapers (20%)Plaster Skyscrapers (30%)Churches (5%)Local Style A houses (15%)Local Style B houses (30%)



Characterization of each template

Constructs the texture for the façades of the buildings by exploiting architectural knowledge assembling architectonical elements

windows, portals, shops, moulding storey, frieze, baseboard, etcThe modeler provides for each floor probabilistic data about elements distribution and textures for each elementsHigher level parameters include the height of the building, the number of floors, the type of roofs, etc.



Parameters’ categories

Vertical structureNumber and height of floor typesGround, first, under roof, other floors

Ground floorType and relevant density of shops, windows and doors

Other floorsType and relevant density of windows, balconies, arches, quoins, plaster. Different statistics for the different types of floors: first, under roof and others.

RoofHeight, ridge, gutter, mansard, etc.



Example



Parameters’ values

For each parameter, the modeler specifies its possible values with the relevant frequency. Frequencies sum up to 1.

The relevant ortho-rectified pictures are to be provided for each value of each item (e.g. type of windows, balconies, etc.) in order for the algorithm to assembly instances of facades based on the statistical description of the architectonic components.



Architectonic parameters



Development tools

The ASA Builder tool is the visual editing tool that implements the ASA algorithm for procedural construction of 3D models



Development tools

A tool chain1- Template CreatorProvide pictures and frequencies for each architectonic

featureOutput: an XML file with all these data

2- Façade BuilderGenerates the 3D models for all the buildings in the

ASA area. Every building is textured with a texture synthetically generated on the basis of the Template Creator statistical description



Genoa



Strasbourg



Resources

www.tieproject.eu [email protected]

fokus k3d 2010

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