Creation of procedural 3D building models can significantly reduce the costs of modeling, since it allows for generating a variety of similar shapes from one procedural description. The common field of application for procedural modeling is modeling of straight building facades, which are very well suited for shape grammars a special kind of procedural modeling system.In order to generate round building geometry, we present a way to set up different coordinate systems in shape grammars. Besides Cartesian, these are primarily cylindrical and spherical coordinate systems for generation of structures such as towers or domes, that can procedurally adapt to different dimensions and parameters. The users can apply common splitting idioms from shape grammars in their familiar way for creating round instead of straight geometry.The second enhancement we propose is to provide a way for users to give high level inputs that are used to automatically arrange and adapt parts of the models. (C) 2017 Elsevier Ltd. All rights reserved.

The creation of building models has high importance, due to the demand for detailed buildings in virtual worlds, games, movies and geo information systems. Due to the high complexity of such models, especially in the urban context, their creation is often very demanding in resources. Procedural methods have been introduced to lessen these costs, and allow to specify a building (or a class of buildings) by a higher level approach, and leave the geometry generation to the system. While these systems allow to specify buildings in immense detail, roofs still pose a problem. Fully automatic roof generation algorithms might not yield desired results (especially for reconstruction purposes), and complete manual specification can get very tedious due to complex geometric configurations. We present a new method for an abstract building specification, that allows to specify complex buildings from simpler parts with an emphasis on assisting the blending of roofs.

Creation of procedural 3D building models can significantly lessen the costs of modeling, since it allows generating a variety of similar shapes from one procedural description. The common field of application for procedural modeling is modeling of straight building facades, which are very well suited for shape grammars – a special kind of procedural modeling system. In order to generate round building geometry, we present a way to setup different coordinate systems in shape grammars. Besides Cartesian, these are primarily cylindrical and spherical coordinate systems for generation of structures like towers or domes, that can procedurally adapt to different dimensions and parameters. The users can apply common splitting idioms from shape grammars in their familiar way, for creating round instead of straight geometry.

Virtual coaching is an application area that allows individuals to improve existing skills or learn new ones; it ranges from simple textual tutoring tools to fully immersive 3D learning situations. The latter aim at improving the learning experience with realistic 3D environments. In highly individual training scenarios it can be beneficial to provide some level of personalization of the environment. This can be supported using procedural modeling that allows to easily modify shape, look and contents of an environment. We present the application of personalization using procedural modeling in learning applications in the project V2me. This project combines virtual and social networks to help senior citizens maintain and create meaningful relationships. We present a system that uses a procedurally generated ambient virtual coaching environment that can be adjusted by training subjects themselves or in collaboration. A small user experience study has been executed that gives first insight to the acceptance of such an approach.

With the current state of video games growing in scale, manual content creation may no longer be feasible in the future. Split grammars are a promising technology for large scale procedural generation of urban structures, which are very common in video games. Buildings with curved parts, however, can currently only be approximated by static pre-modeled assets, and rules apply only to planar surface parts. We present an extension to current split grammar systems that allows the generation of curved architecture through free-form deformations that can be introduced at any level in a grammar. Further subdivision rules can then adapt to these deformations to maintain length constraints, and repetitions can adjust to more or less space.

While the growing demand for new building models contained in virtual worlds, games, and movies, makes the easy and fast creation of modifiable models more and more important, 3D modeling of buildings can be a tedious task due to their sometimes complex geometry. For historic buildings, especially the roofs can be challenging. We present a new method of combining simple building solids to form more complex buildings, and give an emphasis on the blending of roof faces. This can be integrated in common pipelines for procedural modeling of buildings and will bring more expressiveness than existing methods.

Procedural modeling is a technology that has great potential to make the abundant variety of shapes that have to be dealt with in Digital Humanities accessible and understandable. There is a gap, however, between technology on the one hand and the needs and requirements of the users in the Humanities community. In this paper we analyze the reasons for the limited uptake of procedural modeling and sketch possible ways to circumvent the problem. The key insight is that we have to find matching concepts in both fields, which are on the one hand grounded in the way shape is explained, e.g., in art history, but which can also be formalized to make them accessible to digital computers.

We provide a quick and efficient method to project a coherent image that is seamless and perspectively corrected from one particular viewpoint using an arbitrary number of projectors. The rationale is that wide-angle high-resolution cameras have become much more affordable than short-throw projectors, and only one such camera is sufficient for calibration. Our method is suitable for ad-hoc installations since no 3D reconstruction is required. We provide our method as open source solution, including a demonstrative client program for the Processing framework.

Two-dimensional curves are conventionally designed using splines or Bézier curves. Although formally they are C2 or higher, the variation of the curvature of (piecewise) polynomial curves is difficult to control; in some cases it is practically impossible to obtain the desired curvature. As an alternative we propose piecewise clothoid curves (PCCs). We show that from the design point of view they have many advantages: control points are interpolated, curvature extrema lie in the control points, and adding control points does not change the curve. We present a fast localized clothoid interpolation algorithm that can also be used for curvature smoothing, for curve fitting, for curvature blending, and even for directly editing the curvature. We give a physical interpretation of variational curvature minimization, from which we derive our scheme. Finally, we demonstrate the achievable quality with a range of examples.

Shape grammars are the method of choice for procedural modeling of architecture. State of the art shape grammar systems define a bounding box for each shape; various operations can then be applied based on this bounding box. Most notably, the box can be split into smaller boxes along any of its three axes. We argue that a greater variety can be obtained by using convex polyhedra as bounding volumes instead. Split operations on convex polyhedra are no longer limited to the three principal axes but can use arbitrary planes. Such splits permit a volumetric decomposition into convex elements; As convex polyhedra can represent many shapes more faithfully than boxes, shape grammar rules can adapt to a much wider array of different contexts. We generalize established shape operations and introduce new operations that now become possible.

In the course of a project related to green building design, we have created a group of eight parametric building models that can be manipulated interactively with respect to dimensions, number of floors, and a few other parameters. We report on the commonalities and differences between the models and the abstractions that we were able to identify.

Rich metadata is crucial for the documentation and retrieval of 3D datasets in cultural heritage. Generating metadata is expensive as it is a very time consuming semi-manual process. The exponential increase of digital assets requires novel approaches for the mass generation of metadata. We present an approach that is generic, minimizes user assistance, and is customizable for different metadata schemes and storage formats as it is based on generic forms. It scales well and was tested with a large database of digital CH objects.

This chapter contains sections titled: Introduction to 3D Objects Geometry and Semantics: Recipe with Some Open Questions Why are Shape Semantics so Urgently Needed? Description of Geometrical Knowledge Reverse Engineering as Inverse Problem Examples of 3 D Information Extraction Conclusion

Creating 3D content requires a lot of expert knowledge and is often a very time consuming task. Procedural modeling can simplify this process for several application domains. However, creating procedural descriptions is still a complicated task. Graph based visual programming languages can ease the creation workflow, however direct manipulation of procedural 3D content rather than of a visual program is desirable as it resembles established techniques in 3D modeling. In this paper, we present a dataflow language that features a novel approach to handling loops in the context of direct interactive manipulation of procedural 3D models and show compilation techniques to translate it to traditional languages used in procedural modeling. Keywords-procedural modeling, dataflow graphs, loops, term graphs

The development of a European market for digital cultural heritage assets is impeded by the lack of a suitable marketplace, i.e., a commonly accepted distributed exchange platform for digital assets. We have developed such a platform over the last two years, a centralized content management system with distributed storage capability and semantic query functionality. It supports the complete pipeline from data acquisition (photo, 3D scan) over processing (cleaning, hole filling) to interactive presentation, and allows collecting a complete process description (paradata) alongside. In this paper we present the components of the system and explain their interplay. Furthermore, we present and explain which functional components, from transactions to permission management, are needed to operate the system. Finally, we prove the suitability of the API and present a few software applications that use it.

High-quality urban reconstruction requires more than multi-view reconstruction and local optimization. The structure of facades depends on the general layout, which has to be optimized globally. Shape grammars are an established method to express hierarchical spatial relationships, and are therefore suited as representing constraints for semantic facade interpretation. Usually inference uses numerical approximations, or hard-coded grammar schemes. Existing methods inspired by classical grammar parsing are not applicable on real-world images due to their prohibitively high complexity. This work provides feasible generic facade reconstruction by combining low-level classifiers with mid-level object detectors to infer an irregular lattice. The irregular lattice preserves the logical structure of the facade while reducing the search space to a manageable size. We introduce a novel method for handling symmetry and repetition within the generic grammar. We show competitive results on two datasets, namely the Paris 2010 and the Graz 50. The former includes only Hausmannian, while the latter includes Classicism, Biedermeier, Historicism, Art Nouveau and post-modern architectural styles.

We present the prototype of a software system to streamline the serial production of simple interactive 3D animations for the display in museum exhibitions. We propose dividing the authoring process in two phases, a designer phase and a curator phase. The designer creates a set of configurable 3D scene templates that fit with the look of the physical exhibition while the curator inserts 3D models and configures the scene templates; the finished scenes are uploaded to 3D kiosks in the museum. Distinguishing features of our system are the tight integration with an asset repository and the simplified scene graph authoring. We demonstrate the usefulness with a few examples.