In this paper we present a new approach to build typical street networks for urban and rural areas automatically. Most street networks have a characteristic appearance which is a mixture between a kind of a regular spreading of streets and various perturbations of the regular structure, e.g., caused by the terrain. Our City Map Generation (CMG) algorithm gets as input an height field including watercourses and restricted areas such as nature protection areas or mountain areas. Furthermore, the user can specify the urbanization by the number of city centers or by a density map. The CMG algorithm produces a street map for the given landscape based on rules, which the user can also modify to obtain an individual appearance. Additionally, the regular structure is varied by a set of rules incorporating randomness. The results can be used to generate models for city areas, e.g., in movies and commercials. Depending on the demands, our flexible approach can be adjusted to produce a variety of road maps automatically. We show some examples and demonstrate that our algorithm is easy to implement and to use.

This paper presents a novel approach for calculating the carbon footprint in an urban region at the scale of individual neighborhoods. The approach is applied to Maricopa County, Arizona, for two different scenarios of growth. Our strategy for monitoring carbon footprints also involves a new form of visualization that goes beyond the two-dimensional thematic maps and provides better representation of multidimensional spatial data. Our monitoring system includes grid-based calculation and visualization of potential carbon dioxide emissions for future years under different policy and behavioral scenarios. To calculate a total carbon footprint value, we designate several varieties of relevant emissions such as housing expenditure and electricity. We develop datasets and models that allow for accurate calculation of the carbon footprint for Maricopa County. We provide emissions information for different types of housing units and compare the results for different future scenarios of household change. Finally, we visualize the results in three-dimensional representations that take into account the multidimensional dataset. We employ an intuitive approach in constructing three-dimensional surfaces of carbon footprints using B-Splines and Bezier techniques. This 3D representation allows for understanding and comparing multidimensional data using transparency, different layers, and superimposition techniques.

The Double Insertion, Nonuniform, Stationary subdivision surface (DINUS) generalizes both the nonuniform, bicubic spline surface and the Catmull-Clark subdivision surface. DINUS allows arbitrary knot intervals on the edges, allows incorporation of special features, and provides limit point as well as limit normal rules. It is the first subdivision scheme that gives the user all this flexibility and at the same time all essential limit information, which is important for applications in modeling and adaptive rendering. DINUS is also amenable to analysis techniques for stationary schemes. We implemented DINUS as an Autodesk Maya plugin to show several modeling and rendering examples.

Haptic applications are difficult to debug due to their high update rate and man yf actors influencing their execution. In this paper ,w ed escribe ap ractical visual debugger for single-point-of-contact haptic devices of impedance-type. The debugger can easily be incorporated into the running haptic application. The visualization shows the position trajectory with timing infor- mation and associated data lik eg oal positions and computed feedback forces. Also, there are several options for in detail analysis of the feedback force applied at each time instance. We sho ww ith several use cases taken from practical experience that the system is well suited for locating common and intricate problems of haptic appli- cations.

Most of the needs that occur in applications using subdivision surfaces are covered by our hierarchical mesh data structure. We tested the proposed data structure in some implementations for adaptive visualizations where a highly efficient data structure is essential. Primarily, this means our mesh must support a fast hierarchical refinement of the object with a fast access to the vertices in the different subdivision levels. Only the parts of the object with a contribution to the light transport are computed and stored up to an adequate subdivision depth. A rapid and stable navigation on the mesh must be possible, and storing of ancillary information is required. The modular concept of our mesh enables us to exchange the rules of the subdivision scheme easily. With our hierarchical mesh, the rules for Catmull-Clark, Loop and ESubs, which is another subdivison scheme, were easy to implement.

Improving the visual appearance of coarse triangle meshes is usually done with graphics hardware with per-pixel shading techniques. Improving the appearance at silhouettes is inherently hard, as shading has only a small influence there and the geometry must be corrected. With the new geometry shader stage released with DirectX 10, the functionality to generate new primitives from an input primitive is available. Also the shader can access a restricted primitive neighborhood. In this paper, we present a curved surface patch that can deal with this restricted data available in the geometry shader. A surface patch is defined over a triangle with its vertex normals and the three edge neighbor triangles. Compared to PN triangles, which define a curved patch using just the triangle with its vertex normals, our surface patch is G1 continuous with its three neighboring patches. The patch is obtained by blending two cubic Bezier patches for each triangle edge. In this way, our surface is especially suitable for efficient, high-quality tessellation on the GPU. We show the construction of the surface and how to add special features such as creases. Thus, the appearance of the surface patch can be fine-tuned easily. The surface patch is easy to integrate into existing polygonal modeling and rendering environments. We give some examples using Autodesk Maya.®

Zur Modellierung von Freiformflachen im CAD-Unfeld werden zur Zeit hauptsachlich nicht-uniforme rationale B-Spline-Flachen (NURBS) und Unterteilungsflachen verwendet. NURBS-Flachen sind die alteren sowie etablierteren Flachen und werden standardmasig im Industriedesign verwendet. Unterteilungsflachen bieten eine flexiblere Topologie und nutzliche Modellieroptionen, womit sie einen festen Platz in Modellierungspaketen wie z.B. Maya und Cinema4D gefunden haben. Ziel dieser Arbeit ist es, die Vorteile von bikubischen NURBS- und Unterteilungsflachen in einem neuen, erweiterten Unterteilungsflachentyp (ESubs) zu vereinen, um damit ein breiteres Einsatzspektrum in Forschung und Industrie zu erhalten. Catmull-Clark- und bikubische NURBS-Flachen sind in den ESubs durch die Verallgemeinerung enthalten. ESubs bieten jedoch Flachenformen an, die uber die Moglichkeiten von NURBS- und Catmull-Clark- Flachen hinaus gehen. Zu den Kerneigenschaften des neuen Flachentyps ESubs gehoren u.a. die Verwendung einer beliebigen, zwei-mannigfaltigen Topologie, die Generierung einer nicht-uniformen Flache, die Moglichkeit Knotenintervalle einzeln an den Kanten zu modifizieren, sogenannte Special Features und die Verfugbarkeit von Limitpunktregeln. Der zweite Schwerpunkt dieser Arbeit ist die adaptive Visualisierung von Unterteilungsflachen. Sowohl bei der photorealistischen als auch bei der interaktiven Darstellung wird das Objekt adaptiv wahrend des Renderingprozesses verfeinert. Die dazu entwickelten und implementierten Verfahren sind leicht auf weitere Unterteilungsflachentypen ubertragbar und erlauben eine einfache Handhabung von Special Features sowie anderen Regelmodifikationen. Durch die adaptive Verfeinerung werden nur die notwendigen Flachenteile zur Generierung eines qualitativ hochwertigen Bildes berechnet, so dass Rechenzeit und Speicherplatz effizient genutzt werden.

An extended subdivision surface (ESub) is a generalization of Catmull Clark and NURBS surfaces. Depending on the knot intervals and valences of the vertices and faces, Catmull Clark as well as NURBS patches can be generated using the extended subdivision rules. Moreover, an arbitrary choice of the knot intervals and the topology is possible. Special features like sharp edges and corners are consistently supported by setting selected knot intervals to zero or by applying special rules. Compared to the prior nonuniform rational subdivision surfaces (NURSS), the ESubs offer limit-point rules which are indispensable in many applications, for example, for computer-aided design or in adaptive visualization. The refinement and limit-point rules for our nonuniform, nonstationary scheme are obtained via a new method using local Bézier control points. With our new surface, it is possible to start with existing Catmull Clark as well as NURBS models and to continue the modeling process using the extended subdivision options.

For convincing realistic scenes objects with free-form surfaces are essential. Especially for photorealistic rendering pure polygonal models are often not sufficient. We present a new kind of algorithm to render free-form surfaces in a rendering system based on ray tracing. We describe a triangular patch as usual by its three points and normal vectors, but base the intersection calculation as well on the viewpoint of the camera (or, in general, on the ray itself). Hence, the shape of the object depends to some extent on the sampling rays. However, the resulting differences of, for instance, the shape of the silhouette to the shape of the corresponding shadow is usually not perceived by the observer of the rendered image. Because we perform a direct computation without a tessellation process, the resulting surface, its shadows, and its reflections appear smooth independent of the distance to the camera. Furthermore, the memory consumption depends only linearly on the number of input triangles. Special features like creases, T-vertices, and darts are also well supported. The computed uv-coordinates provide a direct means for texture mapping whose visual appearance improves significantly compared to triangle meshes of the same resolution.

For a variety of reasons subdivision surfaces have developed into a prominent member of the family of free-form shapes. Based on a standard polygonal mesh a modeller can build various kinds of shapes using an arbitrary topology and special geometrical features like creases. However, the interactive display of subdivision surfaces in current scenegraph systems based on static levels of detail is unpractical, because of the exponentially increasing number of polygons during the subdivision steps. Therefore, an adaptive algorithm choosing only the necessary quads and triangles is required to obtain high-quality images at high frame rates. In this paper we present a rendering algorithm which dynamically adapts to static surface properties like curvature as well as to view-dependent properties like silhouette location and projection size. Without modifying the base mesh, the method works patchwise and tesselates each patch recursively using a new data structure, called slate. Besides these geometric properties the algorithm can also adapt to the graphics load in order to achieve a desired frame rate in the scenegraph system OpenSG.

Subdivision surfaces have become a standard technique for freeform shape modeling. They are intuitive to use and permit designers to flexibly add detail. But with larger control meshes, efficient adaptive rendering techniques are indispensable for interactive visualization and shape modeling. In this paper, we present a realization of tesselation‐on‐the‐fly for Loop subdivision surfaces as part of a framework for interactive visualization.