Publications and Theses

Thumbnail of Design and Implementation of Web-Based Hierarchy Visualization Services

Design and Implementation of Web-Based Hierarchy Visualization Services

Willy Scheibel, Judith Hartmann, and Jürgen Döllner
10th International Conference on Information Visualization Theory and Applications (IVAPP 2019) 2019, BibTeX

There is a rapidly growing, cross-domain demand for interactive, high-quality visualization techniques as components of web-based applications and systems. In this context, a key question is how visualization services can be designed, implemented, and operated based on Software-as-a-Service as software delivery model. In this paper, we present concepts and design of a SaaS framework and API of visualization techniques for tree-structured data, called H I V I S ER . Using representational state transfer (REST), the API supports different data formats, data manipulations, visualization techniques, and output formats. In particular, the API defines base resource types for all components required to create an image or a virtual scene of a hierarchy visualization. We provide a treemap visualization service as prototypical implementation for which subtypes of the proposed API resources have been created. The approach generally serves as a blue-print for fully web-based, high-end visualization services running on thin clients in a standard browser environment.

Author Version, Slides

Thumbnail of EvoCells – A Treemap Layout Algorithm for Evolving Tree Data

EvoCells – A Treemap Layout Algorithm for Evolving Tree Data

Willy Scheibel, Christopher Weyand, and Jürgen Döllner
9th International Conference on Information Visualization Theory and Applications (IVAPP 2018) 2018, BibTeX

We propose the rectangular treemap layout algorithm EvoCells that maps changes in tree-structured data onto an initial treemap layout. Changes in topology and node weights are mapped to insertion, removal, growth, and shrinkage of the layout rectangles. Thereby, rectangles displace their neighbors and stretche their enclosing rectangles with a run-time complexity of O(n log n). An evaluation using layout stability metrics on the open source ElasticSearch software system suggests EvoCells as a valid alternative for stable treemap layouting.

Author Version, Slides, Handout

Thumbnail of Mixed-Projection Treemaps: A Novel Approach Mixing 2D and 2.5D Treemaps

Mixed-Projection Treemaps: A Novel Approach Mixing 2D and 2.5D Treemaps

Daniel Limberger, Willy Scheibel, Matthias Trapp, and Jürgen Döllner
21st International Conference on Information Visualisation (iV 2017) 2017, BibTeX

2D treemaps are a space-filling visualization technique that facilitate exploration of non-spatial, attributed, tree-structured data using the visual variables size and color. In extension thereto, 2.5D treemaps introduce height for additional information display. This extension entails challenges such as increased rendering effort, occlusion, or the need for navigation techniques that counterbalance the advantages of 2D treemaps to a certain degree. This paper presents a novel technique for combining 2D and 2.5D treemaps using multi-perspective views to leverage the advantages of both treemap types. It enables a new form of overview+detail visualization for complex treemaps and contributes new concepts for real-time rendering of and interaction with mixed-projection treemaps. The technique operates by tilting up inner nodes using affine transformations and animated state transitions. The mixed use of orthogonal and perspective projections is discussed and application examples that facilitate exploration of multi-variate data and benefit from the reduced interaction overhead are demonstrated.

Author Version, Slides

Thumbnail of Attributed Vertex Clouds

Attributed Vertex Clouds

Willy Scheibel, Stefan Buschmann, Matthias Trapp, and Jürgen Döllner
GPU Zen 2017, BibTeX

In todays computer graphics applications, large 3D scenes are rendered which consist of polygonal geometries such as triangle meshes. Using state- of-the-art techniques, this geometry is often represented on the GPU using vertex and index buffers, as well as additional auxiliary data such as tex- tures or uniform buffers. For polygonal meshes of arbitrary complexity, the described approach is indispensable. However, there are several types of simpler geometries (e.g., cuboids, spheres, tubes, or splats) that can be generated procedurally. We present an efficient data representation and render- ing concept for such geometries, denoted as attributed vertex clouds (AVCs). Using this approach, geometry is generated on the GPU during execution of the programmable rendering pipeline. Each vertex is used as the argument for a function that procedurally generates the target geometry. This function is called a transfer function, and it is implemented using shader programs and therefore executed as part of the rendering process. This approach allows for compact geometry representation and results in reduced memory footprints in comparison to traditional representations. By shifting geometry generation to the GPU, the resulting volatile geometry can be controlled flexibly, i.e., its position, parameteri- zation, and even the type of geometry can be modified without requiring state changes or uploading new data to the GPU. Performance measurements suggests improved rendering times and reduced memory transmission through the rendering pipeline.

Author Version, Source Code

Thumbnail of Reducing Visual Complexity in Software Maps using Importance-based Aggregation of Nodes

Reducing Visual Complexity in Software Maps using Importance-based Aggregation of Nodes

Daniel Limberger, Willy Scheibel, Sebastian Hahn, and Jürgen Döllner
8th International Conference on Information Visualization Theory and Applications (IVAPP 2017) 2017, BibTeX

Depicting massive software system data using software maps can result in visual clutter and increased cognitive load. This paper introduces an adaptive level-of-detail (LoD) technique that uses scoring for interactive aggregation on a per-node basis. The scoring approximates importance by degree-of-interest measures as well as screen and user-interaction scores. The technique adheres to established aggregation guidelines and was evaluated by means of two user studies. The first user study investigates task completion time in visual search. The second evaluates the readability of the presented nesting level contouring for aggregates. With the adap- tive LoD technique software maps allow for multi-resolution depictions of software system information. It facilitates efficient identification of important nodes and allows for additional annotation.

Author Version, Slides

Thumbnail of Dynamic 2.5D Treemaps using Declarative 3D on the Web

Dynamic 2.5D Treemaps using Declarative 3D on the Web

Daniel Limberger, Willy Scheibel, Stefan Lemme, and Jürgen Döllner
21st International Conference on Web3D Technology (Web3D '16) 2016, BibTeX

The 2.5D treemap represents a general purpose visualization technique to map multi-variate hierarchical data in a scalable, interactive, and consistent way used in a number of application fields. In this paper, we explore the capabilities of Declarative 3D for the web-based implementation of 2.5D treemap clients. Particularly, we investigate how X3DOM and XML3D can be used to implement clients with equivalent features that interactively display 2.5D treemaps with dynamic mapping of attributes. We also show a first step towards a glTF-based implementation. These approaches are benchmarked focusing on their interaction capabilities with respect to rendering and speed of dynamic data mapping. We discuss the results for our representative example of a complex 3D interactive visualization technique and summerize recommendations for improvements towards operational web clients.

Author Version, Slides, Source Code, Demo

Thumbnail of Interactive Revision Exploration using Small Multiples of Software Maps

Interactive Revision Exploration using Small Multiples of Software Maps

Willy Scheibel, Matthias Trapp, and Jürgen Döllner
7th International Conference on Information Visualization Theory and Applications (IVAPP 2016) 2016, BibTeX

To explore and to compare different revisions of complex software systems is a challenging task as it requires to constantly switch between different revisions and the corresponding information visualization. This paper proposes to combine the concept of small multiples and focus+context techniques for software maps to facilitate the comparison of multiple software map themes and revisions simultaneously on a single screen. This approach reduces the amount of switches and helps to preserve the mental map of the user. Given a software project the small multiples are based on a common dataset but are specialized by specific revisions and themes. The small multiples are arranged in a matrix where rows and columns represents different themes and revisions, respectively. To ensure scalability of the visualization technique we also discuss two rendering pipelines to ensure interactive frame-rates. The capabilities of the proposed visualization technique are demonstrated in a collaborative exploration setting using a high-resolution, multi-touch display.

Author Version, Poster (Portrait), Poster (Landscape)

Thumbnail of Interaktive Visualisierung von hierarchischen, multivariaten und zeitlich variierenden Daten

Interaktive Visualisierung von hierarchischen, multivariaten und zeitlich variierenden Daten

Willy Scheibel
Master's Thesis at the Hasso Plattner Institute, University of Potsdam 2014

A treemap recursively subdivides a two-dimensional area in order to encode a hierarchy and enables the visualization of multiple attributes e.g. with the size, the extruded height or the color of a node. Traditional treemap layout algorithms and rendering techniques can only be used for the comparison of two data sets at different points in time to some extent, as (1) no comparison between nodes in a treemap and between different states is possible and (2) there are no rendering techniques for the size differences of a node over time. This thesis introduces the techniques EvoCell-Layouting, Change Map, and Change Hints. EvoCell-Layouting is a novel treemap layout algorithm that iteratively changes a given treemap layout. Change Maps are density maps to locate changes in attribute values disregarding the difference and the size of the node. Change Hints visualize spatial changes between two states of a treemap. These three techniques enhance the comprehension of the evolution of temporal hierarchical data. A prototypical implementation, a discussion about alternatives, and performance and memory analyses demonstrate real data applicability. An additional case study reveals distinctive changes in the software system of a monitored open-source project that are hard to detect with traditional hierarchy visualizations.

Thesis

Talks & Presentations

02/26/19

Rendering Procedural Textures for Visualization of Thematic Data in 3D Geovirtual Environments
IVAPP 2019, Prague, Czech Republic

02/26/19

Design and Implementation of Web-Based Hierarchy Visualization Services
IVAPP 2019, Prague, Czech Republic

Slides (PDF, 17.3 MiB)

03/07/18

Einführung in die Shared-Memory-Programmierung heterogener Systeme
parallel 2018, Heidelberg, Deutschland

Handout (PDF, 5.1 MiB), Slides (PDF, 8.8 MiB)

01/28/18

EvoCells – A Treemap Layout Algorithm for Evolving Tree Data
IVAPP 2018, Funchal, Madeira, Portugal

Handout (PDF), Slides (PDF)

02/28/16

Interactive Revision Exploration using Small Multiples of Software Maps
IVAPP 2016, Rome, Italy

Poster (Landscape, PDF), Poster (Portrait, PDF)

Teaching

2019 : Summer Term

Fundamentals of Software Analytics
Lecture (MA), Lecturer and Tutor

2018/19 : Winter Term

Introduction to Software Analytics
Lecture (BA/MA), Lecturer and Tutor

Visualization Algorithms & Techniques
Seminar (MA), Tutor

2018 : Summer Term

Gameprogramming
Project Seminar (BA), Lecturer and Tutor

2017/18 : Winter Term

Advanced Development in C++
Project Seminar (MA), Lecturer and Tutor

2017 : Summer Term

Advanced Information Visualization
Seminar (MA), Tutor

2016/17 : Winter Term

Advanced Programming in C++
Lecture (MA), Lecturer and Tutor

Methods and Techniques of Information Visualization
Seminar (MA), Tutor

Real-time Monitoring of Massive Filesystems
Project (MA), Supervisor

2016 : Summer Term

Computergraphics II
Lecture (BA), Tutor

Methods and Techniques of Software Visualization
Seminar (MA), Tutor

Massive Information Mining for Software Analytics
Project (BA), Supervisor

2015/16 : Winter Term

Computergraphics I
Lecture (BA), Tutor

Systems Engineering for Software Analytics
Seminar (MA), Tutor

2015 : Summer Term

Computergraphics I
Lecture (BA), Tutor

Visual Software Analytics
Seminar (MA), Tutor

Programming of Computer Graphics Techniques using C++ and OpenGL
Seminar (BA), Tutor and Co-Lecturer

Software Analytics
Project (BA), Supervisor

2014/15 : Winter Term

Computergraphics II
Lecture (BA), Tutor

Visualization for Interactive Software Analytics
Seminar (MA), Tutor

Automated Visual Software Analytics
OpenHPI Course, Tutor

Software Analytics
Project (BA), Supervisor

2014 : Summer Term

Information Visualization
Seminar (MA), Co-Tutor

Graphics Programming using OpenGL and C++
Seminar (BA), Co-Tutor and Co-Lecturer

2013/14 : Winter Term

Software Analysis and Visualization
Seminar (MA), Co-Tutor

Contact

E-Mail:

willyscheibel@gmx.de

Other: willy.scheibel@hpi.de, willy.scheibel@cginternals.com

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