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The paper reports on the 40 years of development of Computer Graphics and, more recently, Visual computing (VC) at the Technische Universität Darmstadt in Germany, from its beginning in 1975 to the leading “Computer Graphics and Visual Computing Hub” in Europe as of 2014. This development is described along three axes. First, the institutional development and its rational to establish Computer Graphics as a discipline of Computer Science and as an enabling technology for developing our Knowledge Society, are described. Second, the scientific and technological impact based on the teaching activities and the large number of theses submitted in Darmstadt for the area during these 40 years are addressed. Finally, the research road maps of the Computer Graphics and Visual Computing Hub in Darmstadt are presented relatively to the different stages of CG and VC research, relatively to a scientific view to the large number of projects implemented over these 40 years and, finally, also relatively to the project results as seen from the media. In order to manage the quantity as well as the complexity of the information available, the description of these road maps is divided in four time periods: 1975–1984, 1985–1994, 1995–2004 and 2004–2015. The paper also gives the view of the authors on how they see the future of Computer Graphics and Visual Computing. At the end, the paper includes an extensive list of references for the reported content. [ABSTRACT FROM AUTHOR]

This paper presents a sketch-based mesh extrusion method, which is useful for intuitive, efficient geometric modeling of freeform polygonal objects. With our method, the user can extrude either a closed or open surface from the surface or the boundary of a given mesh by sketched input. Thus, compared to earlier methods, our method provides more flexibility for solving surface modeling problems. Our mesh extrusion algorithm consists of four steps: (1) create a base curve; (2) project extruding strokes; (3) sweep a base curve; and (4) sew adjacent curves. At the end of this paper, examples of our mesh extrusion implementation are shown to demonstrate its functionality. Our freeform extrusion has been implemented as a part of our sketch-based modeling system, and the mesh extrusion can be completed in real time on a standard PC. [Copyright &y& Elsevier]

Haptic technologies allow for adding a new “touching” modality into virtual scenes. 3D reconstruction of a real life scene results, however, often in millions of polygons which cannot be simultaneously visualized and haptically rendered. In this paper, we propose a way of haptic interaction with real life scenes where multiple original images of the real scenes are augmented with reconstructed polygon meshes. We present our solution to the problems of haptic model alignment with the images and interactive haptic rendering of large polygon meshes with reconstruction artifacts. In particular, the presented collision detection algorithm is not restricted by any hypothesis and robust enough to support smooth interaction with millions of polygons. The feasibility and usability of the proposed solution is evaluated in a user study. [ABSTRACT FROM AUTHOR]

Abstract: Decomposing a shape into visually meaningful parts comes naturally to humans, but recreating this fundamental operation in computers has been shown to be difficult. Similar challenges have puzzled researchers in shape reconstruction for decades. In this paper, we recognize the strong connection between shape reconstruction and shape decomposition at a fundamental level and propose a method called . The generates a space of decompositions parameterized by , the diameter of a circle convolved with the input polygon. As we vary the value of , some structural features appear and disappear quickly while others persist. Therefore, by analyzing the persistence of the features, we can determine better decompositions that are more robust to both geometrical and topological noises. [Copyright &y& Elsevier]

Abstract: In this paper, we present a novel parallel algorithm for computing the convex hull of a set of points in 3D using the CUDA programming model. It is based on the QuickHull approach and starts by constructing an initial tetrahedron using four extreme points, discards the internal points, and distributes the external points to the four faces. It then proceeds iteratively. In each iteration, it refines the faces of the polyhedron, discards the internal points, and redistributes the remaining points for each face among its children faces. The refinement of a face is performed by selecting the furthest point from its associated points and generating three children triangles. In each iteration, concave edges are swapped, and concave vertices are removed to maintain convexity. The face refinement procedure is performed on the CPU, because it requires a very small fraction of the execution time (approximately 1%), and the intensive point redistribution is performed in parallel on the GPU. Our implementation outpaced the CPU-based Qhull implementation by 30 times for 10 million points and 40 times for 20 million points. [Copyright &y& Elsevier]

Abstract: It is a unique challenge to teach programming and application development to students pursuing an IT degree other than computer science. Using simple visual computing as a medium to teach programming can be very helpful in such situations as it enables programmes that produce pictures rather than raw text and data. This paper describes a semester-long experience of using image processing as the theme in a course to teach programming and program design to students of information systems. Students progressively built a fairly complete image processing application from scratch in a bottom-up fashion using Java. They first concentrated on using low-level constructs like arrays and implemented several operations on them, and then supplemented their programs with features like a GUI complete with “undo–redo” features and capabilities to handle most standard image file formats. Not only did this approach satisfy all the objectives of a typical programming course but also enabled students to develop meaningful applications from scratch with “standard” features. Our classroom was composed of a mix of undergraduate and graduate students lacking sufficient programming background. A comparative analysis shows improvement in student performance when using image processing rather than not. With minor variations, our approach can be fit to courses for other majors where programming is considered useful but not critical. [Copyright &y& Elsevier]

Abstract: The creation and the evaluation of aesthetic artifacts are tasks related to design, music and art, which are highly interesting from the computational point of view. Nowadays, Artificial Intelligence systems face the challenge of performing tasks that are typically human, highly subjective, and eventually social. The present paper introduces an architecture which is capable of evaluating aesthetic characteristics of artifacts and of creating artifacts that obey certain aesthetic properties. The development methodology and motivation, as well as the results achieved by the various components of the architecture, are described. The potential contributions of this type of systems in the context of digital art are also considered. [Copyright &y& Elsevier]

Abstract: In many situations, individuals or groups of individuals are faced with the need to examine sets of documents to achieve understanding of their structure and to locate relevant information. In that context, this paper presents a framework for visual text mining to support exploration of both general structure and relevant topics within a textual document collection. Our approach starts by building a visualization from the text data set. On top of that, a novel technique is presented that generates and filters association rules to detect and display topics from a group of documents. Results have shown a very consistent match between topics extracted using this approach to those actually present in the data set. [Copyright &y& Elsevier]

Abstract: During the past several years, considerable work has been presented on the methods for measuring and modeling the observed reflectance properties of materials. However, most of these works have been done under controlled lighting configurations, and require a constant bidirectional reflectance distribution function (BRDF), which is a measure of the amount of light scattered by a medium from one direction into another, or a homogeneous material over the object regions. This paper discusses a method to estimate the reflectance properties of a textured object under uncontrolled illumination. Assuming that the object has a constant specular reflectance property over its surface, the BRDF can be approximated as a constant specular component and a spatially varying diffuse component. The proposed method will first approximate the illumination distribution of a scene from a set of high dynamic range (HDR) radiance maps of a light probe. Next, a patch on the surface of an object is selected; several HDR intensity maps of the patch taken under different viewing conditions are used to estimate the average specular reflectance parameters of this patch. With the separation of the specular component and the diffuse component of each sample, and using the separated diffuse component, the diffuse reflectance parameters for each point over the surface are next estimated. The test results show that the method is effective for textured objects with constant specular reflectance properties. The method can also be directly applied to objects with piecewise-smooth material, which means that although the surface of an object does not have a constant specular reflectance property; when sub-divided into many smaller meshes, the specular parameter of each mesh can be regarded as uniform. [Copyright &y& Elsevier]

Abstract: This paper presents a novel technique named pseudo surface-texture synthesis (PSTS), which is capable of providing a target surface with textured appearance. Instead of placing texture images directly on the target surface, as in classic texture mapping/synthesis, this method takes place purely in 2D image space—it generates a 2D texture with projective variation to mimic the effect of the texture being on the surface. It is applicable to arbitrary 3D surfaces. The advantage of PSTS is that it can avoid a considerable amount of operations on the target surface required by the classic texture techniques, thus providing programming simplicity and fast performance. Within PSTS, a new 2D adaptive texture synthesis method is proposed, which is able to generate optimised textures using adaptive neighbourhoods. Experimental results are provided. [Copyright &y& Elsevier]

Abstract: In this paper, we report on five years of teaching experience with our introductory course “Graphical-Interactive Systems”, which covers basic topics of human–computer interaction and computer graphics for students in the third year of their major in computer science. Although the two fields of human–computer interaction and computer graphics are usually taught in different courses, we believe that they have much in common and can therefore be integrated into a combined course. “Graphical-Interactive Systems” builds a foundation for advanced courses in both disciplines and achieves an efficient use of teaching time due to synergy effects. [Copyright &y& Elsevier]

Abstract: This paper studies how Computer Graphics (CG) is taught and proposes a course on 2D CG and Image Processing (IP) as an alternative to the traditional 3D CG course. This unconventional course is motivated by an analysis of more than 70 Computer Science curricula. This analysis considers many aspects: CG, IP, and Human–Computer Interaction courses; curricula such as Computer Engineering, Computer Science, Information Technology, and Software Engineering; the difference between introductory and advanced courses; and universities known for their leadership in CG as well as mainstream universities. The analysis suggests that, given the different types of universities and curricula, there should be more alternative courses tailored to the needs of particular curricula. Developing such courses can be difficult and time consuming, so a methodology is proposed to describe a course with information useful for others who could be selecting it or who could be putting it in practice. This methodology is put in practice with the description of a course on 2D CG and IP. [Copyright &y& Elsevier]

Very large polygonal models are frequently used in scientific computing, mechanical engineering, or virtual medicine. An effective technique to handle these large models is occlusion culling. Like most large model techniques, occlusion culling trades overhead costs with the rendering costs of the possibly occluded geometry.In this paper, we present occlusion culling techniques for OpenSG. These techniques utilize OpenGL or OpenGL extensions to determine occlusion information. Techniques utilizing image-space and temporal coherence are used to optimize occlusion query efficiency. Only the standard OpenSG data structures are used and no precomputation is necessary for the presented techniques. [Copyright &y& Elsevier]

This paper presents a new approach to carry out erosion, dilation and connected component labeling. We use the extreme vertices model, an orthogonal polyhedra representation, to describe binary images and volume data sets in a very efficient way.Our proposal does not use a voxel-based approach but deals with the inner sections of the object. It allows to treat images and volumes indistinctly using the same algorithm and data structure with no overhead of memory and can be applied to manifold as well as non-manifold data. The connected component labeling algorithm actually detects non-manifold zones and permits to break or not the objects at these zones by an user-specified parameter. [Copyright &y& Elsevier]

This paper presents a general method for selectively refining or coarsening progressive meshes. Our method works for arbitrary meshes, deals with non-manifolds, and allows the change of manifold and genus properties of the mesh. We introduce new definitions for edge contraction and expansion operations, which make solely use of the vertex hierarchy. These definitions in conjunction with their legal conditions lead to many provable properties of the refinement process. In addition, we propose a locally re-stripping method to dynamically generate the strips during selective refinements, which efficiently forms strips for meshes coarsening or refining process. [Copyright &y& Elsevier]

Demonstration programs have a long and storied history in the field of computer science education. This is particularly true in the area of computer graphics where the displays are often worth more than the proverbial “thousand words”. A suite of such programs was presented at the SIGGRAPH conference in Los Angeles during the summer of 2001. This paper reviews that suite, and discusses its further development. It also discusses the pedagogical role of such programs within the field of computer graphics education, including contributions of some analogous suites currently available. [Copyright &y& Elsevier]

Recently, we proposed a new isosurface extraction algorithm that extracts portions of the isosurface in a view-dependent manner by ray casting and propagation. The algorithm casts rays through a volume to find visible active cells as seeds and then propagates their polygonal isosurface into the neighboring cells. Small pieces of the isosurface are generated by distance-limited propagation and joined together to form the final surface. This paper presents our evaluation of several design choices of the algorithm. We have implemented these design choices and showed that by making right design decisions, we can substantially reduce the time to obtain most (such as 99.9%) of the isosurface. [Copyright &y& Elsevier]

Foreword to Special Section on VriPhys2017, containing extended best papers. [ABSTRACT FROM AUTHOR]