Procedural Modelling

Procedural modeling deals with (semi-)automatic content generation by means of a program or procedure. Among other advantages, its data compression and the potential to generate a large variety of detailed content with reduced human intervention, have made procedural modeling attractive for creating virtual environments increasingly used in movies, games, and simulations. We survey procedural methods that are useful to generate features of virtual worlds, including terrains, vegetation, rivers, roads, buildings, and entire cities. In this survey, we focus particularly on the degree of intuitive control and of interactivity offered by each procedural method, because these properties are instrumental for their typical users: designers and artists. We identify the most promising research results that have been recently achieved, but we also realize that there is far from widespread acceptance of procedural methods among non-technical, creative professionals. We conclude by discussing some of the most important challenges of procedural modeling. PM has the potential to drastically reduce the amount of modeling effort required to create digital content. Furthermore, because its methods are often stochastic, PM can create a variety of results from one set of input parameters; e.g., a large number of tree models, all of the same species and age, but each with a unique structure and shape.

In the past decade, digital technologies had a great impact on contemporary architectural practice, design and theory. CAD/CAM technologies opened up new opportunities by allowing design and production of complex geometric shapes. One of
the first applications of computational process in architecture was based on using shape grammars, a rule-based expert systems in artificial intelligence generating geometric shapes. Early applications of shape grammars in art and architecture
started shortly after its invention during the 70ies and 80ies of the XX century, however, their potential as a generative design tool still has not been fully exploited in practice. Despite their popularity in academic circles, shape grammars have not found
a widespread place/usage in computer aided architectural design.
Role of shape grammar as a generative design and analysis tool and their influence on
contemporary architectural design and theory are examined in this paper. Also, new and ongoing issues concerning shape grammars are discussed in order to indicate further directions of their usage

This article outlines a new semi-automatic approach for generating accurate BIM facade models for existing buildings from laser and image data. Two new developments for as-built BIM modelling are presented in this article. The first is a new library of reusable parametric objects designed for modelling classical architectural elements from survey data. These library objects are dynamic and have parameters that can instantly alter the shape, size and other properties of objects. The parametric architectural objects have been designed from historic manuscripts and architectural pattern books. These parametric objects were built using an embedded programming language within the ArchiCAD BIM software called Geometric Description Language (GDL). The second development which is described in more detail in this article is a complete parametric building façade. This parametric building facade can be used as a template for fast and efficient generation of BIM facade geometry. The design of this parametric façade incorporates concepts from procedural modelling which is an automated approach to generating 3D geometries based on rules and algorithms. Parametric architectural objects are automatically combined with rules to generate many different façade arrangements which are controlled by user parameters. When automatically generating a façade, the initial position and size of elements are estimated using classical architectural proportions. Object can then be graphically edited individually or in groups to match the computer generated geometry to survey data. The parametric façade template has also been implemented with the Geometric Description Language for ArchiCAD BIM software. This enables the tools developed to utilise the full benefits of BIM software which includes automated construction or conservation documents, semantic object oriented objects based on IFC semantic classes, automatic lists of objects and material and the ability to add and link additional information to the model. Initial user tests have indicated that the parametric façade is more efficient than previous methods for creating accurate façade models from survey data. The façade template also provides an easier solution for generating façade models when compared to existing methods. Non-specialist users with little experience in 3D modelling can easily generate and modify the façade template by altering parameters graphically or from a dialogue box.

It is a challenge for shape grammars to incorporate spatial hierarchy and interior connectivity of buildings in early design stages. To resolve this difficulty, we developed a bi-directional procedural model: the forward process constructs the derivation tree with production rules, while the backward process realizes the tree with shapes in a stepwise manner (from leaves to the root). Each inverse-derivation step involves essential geometric-topological reasoning. With this bi-directional framework, design constraints and objectives are encoded in the grammar-shape translation. We conducted two applications. The first employs geometric primitives as terminals and the other uses previous designs as terminals. Both approaches lead to consistent interior connectivity and a rich spatial hierarchy. The results imply that bespoke geometric-topological processing helps shape grammar to create plausible, novel compositions. Our model is more productive than hand-coded shape grammars, while it is less computation-intensive than evolutionary treatment of shape grammars.

The grammar-based procedural modelling technology 'CGA Shape' allows the creation of parametric architectural models that can be adapted through both user input and probabilistic processes, and thus can be used to generate alternative visualisations of buildings based on archaeological data. We explore the capacity of this technology to model and communicate the interpretative uncertainty inherent in the process of archaeological visualisation. A review of previous applications of CGA Shape within cultural heritage demonstrates its potential for uncertainty visualisation, but also shows limited incorporation of large, detailed and complex archaeological datasets. The technology is thus assessed through a case study, the reconstruction of a possible ship-shed from the site of Portus, which comprises a heterogeneous dataset based on geophysical, archaeological, architectural and artistic sources. The strengths and limitations of this approach are assessed, considering its influence on interpretative processes, communicative ability, and its potential to provide transparency in the modelling methodology.

Plants and plant organs are commonly modeled using skeletal techniques. Plant structure is then described in terms of axes, around which limb surfaces are built using standard geometric modeling techniques, such as generalized cylinders or implicit surfaces. In this research, an alternative, based on the use of subdivision techniques, is described. The approach is to build a simple polygon mesh around the skeleton and use a surface subdivision algorithm to get a smooth surface. Special attention is given to the modeling of surfaces surrounding branching points. It is shown that subdivision surfaces provide a useful alternative to approaches based on implicit surfaces. The method is illustrated using models of tree branches and compound leaves.

The amount of 3D modelling applications in archaeology has increased enormously over the last decade. 3D recording techniques allow researchers to quickly and accurately document archaeological evidence, and 3D reconstructions have created new possibilities to communicate the results to a larger public. In this latter case, however, numerous scholars have expressed their concern regarding the ethics of such digital representations, since they give prominence to a crystallized image of the past and do not account for the complexity of the archaeological record. The study presented here aims to make a practical contribution to a new understanding and use of 3D reconstructions, namely as ‘laboratories’ to test hypotheses and visualize, evaluate and discuss alternative interpretations.

In order to do so, an analysis of visual reconstructions of the early and late modern period is presented first, followed by a discussion of current applications of 3D digital reconstructions, with a special focus on cityscapes. Lastly, a practical implementation of a research-driven, intellectually transparent and GIS-based 3D reconstruction is proposed for the urban site of Koroneia, in Boeotia, Central Greece. Specifically, the methodology developed in this work uses tools that are employed in geo-design and modern urban planning in an innovative way, integrating GIS with a rule-based modelling approach. With a strong focus on the automation and iteration of the reconstruction process, our 3D visualization provides an intuitive insight into hidden relationships and associations among data, and allows the creation and evaluation of alternative reconstruction hypotheses.     


Full text available in Open Access here:
http://www.archaeopress.com/public/displayProductDetail.asp?id=%7B3E4846F9-77FD-4A15-A264-24267D731E58%7D   


Supplementary material (CityEngine rule files and assets) available here: https://github.com/cpiccoli/rules

Over the years, there has been an increasing exploitation of 3D visualizations in archaeology. These 3D models are mostly used to communicate the archaeologist’s interpretation to the public by visualizing the fragmentary and often puzzling archaeological evidence in a more understandable and appealing way. However, the use of 3D visualizations as a means to present archaeological sites to the public has  overshadowed their application as a research tool during archaeological investigation. In fact, 3D reconstructions have mostly been used at the end of the archaeological study when the research and interpretation had already been completed, thus excluding them from the cycle of knowledge generation. A recent academic trend aims to counterbalance this tendency by demonstrating that 3D visualizations contribute to the archaeological evidence in a holistic way and make it possible to discover new relationships and patterns in the archaeological data, trigger new research questions and test alternative hypotheses.
This article discusses the scientific role of 3D visualizations taking as a case study the current project of the reconstruction of the ancient town of Koroneia, Greece, that is carried out at Leiden University. The research is based on the combination of GIS data and procedural modelling techniques and aims to offer a tool that supports the ongoing survey of the ancient site by organizing the available data and visualizing possible reconstruction hypotheses on the ancient city layout. By following the methodology illustrated here, the 3D visualization is not an isolated outcome of the archaeological investigation, but becomes an integral part of the data interpretation and the hypothesis generation processes.

Urban surveys investigate past cityscapes by integrating heterogeneous data sources such as architectural documentation, pottery collection and geophysical prospections. Handling such complex data sets and combining them in order to obtain a coherent picture of the ancient spatial structure is challenging. This paper presents the preliminary results of the creation of a 3D GIS of the ancient town of Koroneia (Boeotia, Greece), which is currently being investigated using non-destructive methods within the Ancient Cities of Boeotia project. The workflow consists of two phases: 1) mapping of the finds onto the DEM of the hill to visualize their distribution and characteristics as recorded during fieldwork; 2) reconstructing the ancient terrain and the possible layout of the town in the 4th century BC. To tackle this task, we have adopted a novel methodology, which is based on the combination of GIS and procedural modelling. Specifically, a set of procedural rules was written, which represent a formal and parametric description of Classical Greek architecture. An additional rule was created to automatically visualize the properties of the architectural finds in ArcGIS. This approach allows us to quickly update the 3D visualization when new data become available and to test alternative reconstruction hypotheses. Moreover, this implementation enables the creation of an intellectually transparent 3D reconstruction and forms the basis for a quantitative analysis of the built environment.

Plants and plant organs are commonly modeled using skeletal techniques. Plant structure is then described in terms of axes, around which limb surfaces are built using standard geometric modeling techniques, such as generalized cylinders or implicit surfaces. In this research, an alternative, based on the use of subdivision techniques, is described. The approach is to build a simple polygon mesh around the skeleton and use a surface subdivision algorithm to get a smooth surface. Special attention is given to the modeling of surfaces surrounding branching points. It is shown that subdivision surfaces provide a useful alternative to approaches based on implicit surfaces. The method is illustrated using models of tree branches and compound leaves.

In the digital era, our interactions with technology are mediated by the varying properties of hardware, software, data types, user interface design (UI), user experience design (UX), and workflows that shape our practices, which in turn impacts not only our interpretations, but more importantly the potentiality of our interpretations. Since Gibson (1977) and Norman (1988), diverse disciplines ranging from narrative studies to design studies to archaeology have employed the affordance concept (albeit in varying ways and not without debate, for example, as a theoretical framework for research and practice.  In the Keeping Data A live (KDA) project, we focused on the potential opportunities and hindrances afforded by infrastructures and workflows for 3D procedural modeling, taking up the call of Perry and Taylor (2018) and long-term advocacy by Huggett (for example, 2015; 2020) to engage in a reflexive process to theorize our digital research practices. This process of reflexive exploration focused our attention on how procedural modelers work with 3D models through the infrastructure and what they considered important or valuable. It highlighted the need to look beyond the engagements of individual modelers with data, metadata, and paradata and account for the strongly collaborative and interactive character of this community’s practices. To truly support these collaborative practices, looking forward we must build infrastructures that afford and encourage their users to engage with one another, as well as the 3D models, metadata, and paradata they create.

In the past decade, digital technologies had a great impact on contemporary architectural practice, design and theory. CAD/CAM technologies opened up new opportunities by allowing design and production of complex geometric shapes. One of the first applications of computational process in architecture was based on using shape grammars, a rule-based expert systems in artificial intelligence generating geometric shapes. Early applications of shape grammars in art and architecture started shortly after its invention during the 70ies and 80ies of the XX century, however, their potential as a generative design tool still has not been fully exploited in practice. Despite their popularity in academic circles, shape grammars have not found a widespread place/usage in computer aided architectural design. Role of shape grammar as a generative design and analysis tool and their influence on contemporary architectural design and theory are examined in this paper. Also, new and ongoing issues con...

While the creation of convincing cityscapes from the outside is already possible, there is a lack of robust and
efficient techniques for modeling the interior of buildings. In particular, we focus on challenges for the subdivision
of the interior space into rooms and for placement of furniture in those rooms.

This paper will deal with a new approach for the reconstruction of archaeological urban contexts and its implementation on the web. Starting from archaeological information, geospatial and topographic interactive content exploration. The process involves semi-automatic steps to provide a multidisciplinary environments. Optimized data and a well-structured 3D world have the primary goal of web accessibility of virtual archaeology. Our main aim is to recreate entire ancient urban contexts and landscapes and make them accessible via the web. To achieve this goal, we successfully used a procedural approach, with the software CityEngine, for low poly modelling of a huge number of buildings. In fact, this method which allow the user to completely control all entities in the hierarchy of the scene. In this way we can scripts to easily simulate the distribution and randomness of the elements.

To the best of our knowledge, the idea of city has grown beyond its physical concept. The advent of the Internet and the growing development of Information and Communications Technology (ICT) have gradually replaced the traditional ways of representing urban space by digital 3D smart models.
In this paper we intend to highlight the contribution of City Information Models (CIM) in experiencing the architectural design of sites and cities, in past and present scenarios. Our study case is the Lisbon downtown area (also known as Baixa Pombalina – Pombaline Downtown), rebuilt after the 1755 earthquake and submitted for the UNESCO's World Heritage tentative list in 2004. Characterised by the orthogonality of its street network and the modularity of its façades, it is an area with a large potential for the application of parametric models to simulate different epochs.
Regarding this characteristic, a CIM model has been created for the study area, using ESRI's CityEngine tools by combining BIM features in a GIS environment. Attributes such as building age, use, preservation and façade covering were added to enhance the model as well as different levels of detail according to historical epochs. In addition, the model allows the automatic extraction of new parameters, such as the block volume and the building gross area, which are not directly obtainable in a GIS environment.
Data dissemination was also considered, as the used software provides tools to publish the model on a web environment, by choosing the information to deliver, allowing a full data access to qualified users, by (as simple as) “swiping” the line.

The complexity of modern urban environments and civil demands for fast, reliable and affordable decision-making requires not only a 3D Land Information System, which tends to replace traditional 2D LIS architectures, but also the need to address the time and scale parameters, that is, the 3D geometry of buildings in various time instances (4<sup>th</sup> dimension) at various levels of detail (LoDs - 5<sup>th</sup> dimension). This paper describes and proposes solutions for technical aspects that need to be addressed for the 5D modelling pipeline. Such solutions include the creation of a 3D model, the application of a selective modelling procedure between various time instances and at various LoDs, enriched with cadastral and other spatial data, and a procedural modelling approach for the representation of the inner parts of the buildings. The methodology is based on automatic change detection algorithms for spatial-temporal analysis of the changes that took ...

How to qualify the built urban form if it is mostly composed of private buildings and therefore hardly influenced by public urban designs, especially in consolidated urban fabric? To progress in this challenge, we propose a reflection on the current urban rules and the traditional planning. Given the rigidity of the traditional methods of establishing urban occupation indexes, the main objective of this study is to assess the relevance of a flexible methodology - using parameter-based measurement and prescription of urban form, employed in procedural urban modeling software - to think over the mechanisms of territorial regulation. As a tool to actualize this method we chose to use the Esri CityEngineTM, tridimensional modeling software specialized in urban environment generation from a set of predefined rules. His procedural methodology - through a programming language called CGA (Computer Generated Architecture) - allows you to change the rules and urban indicators as necessary to make room for new design possibilities. Using the software, we modeled three scenarios: two analytical ones, illustrating the existing situation and the neighborhood's current legislation application and an alternative design exercise from the elaboration of different sets of CityEngineTM rules and their application on buildable areas.

The complexity of modern urban environments and civil demands for fast, reliable and affordable decision-making requires not only a 3D Land Information System, which tends to replace traditional 2D LIS architectures, but also the need to address the time and scale parameters, that is, the 3D geometry of buildings in various time instances (4<sup>th</sup> dimension) at various levels of detail (LoDs - 5<sup>th</sup> dimension). This paper describes and proposes solutions for technical aspects that need to be addressed for the 5D modelling pipeline. Such solutions include the creation of a 3D model, the application of a selective modelling procedure between various time instances and at various LoDs, enriched with cadastral and other spatial data, and a procedural modelling approach for the representation of the inner parts of the buildings. The methodology is based on automatic change detection algorithms for spatial-temporal analysis of the changes that took ...

We propose a system to simulate, analyze and visualize occupant behavior in urban environments, combining parametric modeling and agent--based simulation. A procedurally generated 3D city model, containing semantic information about the functions and behaviors of buildings, gets automatically populated with artificial agents representing pedestrians, cars and public transport vehicles interacting with the built environment and each other. The system identifies empiric correlations amongst: functions of buildings and other urban elements, population density, utilization and capacity of the public transport network, and congestion effect on the street network. Practical applications include the assessments of a) bottlenecks, b) public transit efficiency, c) amenities accessibility, d) level of service of public transport and the traffic network, as well as e) the stress and exhaustion of pedestrians. All these aspects ultimately relate to the quality of life within the given urban areas.

The aim of this work is to provide researchers within the fields of urban history or archaeology and also urban planners and designers, with a framework to recreate, simulate and compare scenarios for an urban area with a significant heritage value.
Our study case is the Downtown Lisbon (also known as Baixa Pombalina), rebuilt after the 1755 earthquake and submitted for the UNESCO World Heritage Tentative List in 2004. Characterized by the orthogonality of its urban fabric and the modularity of its facades, it is an area with a large potential for the application of parametric models.

In a single city model we present three scenarios: i) the pre-earthquake city; ii) the rebuilding Plan city and iii) the current city. The model includes some geometrical parameters allowing the user to compare scenario attributes.

This is a work in progress.

Credits:

Sónia Ildefonso
Helena Rua
Ana Paula Falcão