Scientific Visualization and Computer Graphics

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# Jasper van de Gronde

• room number: 491 (Bernoulliborg, building 5161)
• e-mail: j.j.van.de.gronde rug.nl

## Research interests

I am interested in all sorts of image processing topics, including compressed sensing, linear and morphological filters, and deep learning, with a special interest in applications on large/high-dimensional and non-scalar data. Making proper use of vector- or tensor-valued data, possibly as an intermediate step, also interests me greatly, as does the interplay between (mostly) linear approaches and morphological approaches. My PhD thesis was on morphological operators for tensor images, exploring shape and structure in movement and direction dependence. I defended my thesis on 30 June 2015, and am currently a post-doc.

Tensor images (or volumes) are just like ordinary images or volumes, except that at each point we have a vector or matrix (tensors are essentially a generalization of vectors and matrices). To visualize a tensor image with matrices at each position, we typically use "glyphs": for each position a small glyph is drawn whose shape represents the matrix (S). The glyph is often a unit sphere deformed in such a way that each vector v on the unit sphere is given the magnitude v.(S.v). Below you can interact with a live demonstration of this technique (requires a WebGL capable browser, I recommend Firefox, and possibly some patience):

 WebGL based demonstration of tensor field glyphs Rotating Click and drag. Zooming Press +/- or use mousewheel. Glyph resizing Hold Ctrl and zoom. Press 'u' to make all glyphs approximately the same size. Cutting plane Press 'c'. The plane will be parallel to the screen and through the origin. In this case, the matrices describe stresses at atomic positions in a nanowire (courtesy of S.S.R. Saane, Micromechanics group, RuG). Blue shows positive values(/radii), while orange shows negative values.

## Demos

Apart from the rendering above, here is some more code you can try out both in the browser and using Node.js:

There are also some demos that can only be run off-line:

Various projects not (necessarily) associated with a particular publication can be found on Github (also see the SciJS repository).

I maintain a bibliography of work done on both colour morphology and tensor morphology (note that I'm not too strict about what classifies as "colour" morphology). I try to subclassify (using tags) papers based on what kind of method they use. If you feel anything is missing or wrong, please let me know.

An interesting (informal) discussion of the problem of finding a total order for colours can be found here. Note that most of the approaches discussed there indeed correspond to actual algorithms that have been tried in mathematical morphology (and the overview is even fairly, although not entirely, complete). In particular, people have experimented with methods similar to the Hilbert curve approach (Chanussot1998), as well as the travelling salesman approach (Florez2005, Chevallier2014). But note that Chevallier has shown that any total order is necessarily discontinuous when computing joins and meets (this is part of the reason why much of my thesis is focussed on making partial orders more palatable).

Although I tend to talk about product orders and lexicographical orders, there are many more related concepts, as well as different terms for the same concepts. To clarify, I have made a short summary of different terms and in which context they are used.

## Publications

1. Ji, Chengtao, Gronde, Jasper J. van de, Maurits, Natasha M. and Roerdink, Jos B. T. M (2019) Visual Exploration of Dynamic Multichannel EEG Coherence Networks.. . (URL) (BibTeX)
2. Soancatl Aguilar, Venustiano, van de Gronde, Jasper J., Lamoth, Claudine J. C., Maurits, Natasha M. and Roerdink, Jos B. T. M. (2018) Assessing Postural Control Performance during Exergaming based on Speed and Curvature of Body Movements.. . Attach:pdf.gif Δ Δ (BibTeX)
3. Soancatl Aguilar, Venustiano, J. van de Gronde, Jasper, J. C. Lamoth, Claudine, van Diest, Mike, M. Maurits, Natasha and B. T. M. Roerdink, Jos (2017) Visual Data Exploration for Balance Quantification in Real-Time During Exergaming.. . (URL) (BibTeX)
4. Chengtao Ji and Jasper J. van de Gronde and Natasha M. Maurits and Jos B. T. M. Roerdink (2017) Visualizing and Exploring Dynamic Multichannel EEG Coherence Networks. In {VCBM} 17: Eurographics Workshop on Visual Computing for Biology and Medicine, Bremen, Germany, September 7-8, 2017.. Eurographics Association, pages 63-72. Honorable Mention Award. (URL) (BibTeX)
5. Soancatl Aguilar, Venustiano, van de Gronde, Jasper J., Maurits, Natasha M., Lamoth, Claudine C. J. C. and Roerdink, Jos B. T. M. (2016) Curvature and Speed for Balance Quantification During Exergaming. In Proceedings of the 9th International Conference on Motion in Games. New York, NY, USA. ACM, pages 201-202. (URL) (BibTeX)
6. Soancatl Aguilar, Venustiano, van de Gronde, J. J. and Lamoth, C. J. C., Maurits, N. M. and Roerdink, Jos B. T. M. (2016) Visual Data Exploration for Balance Quantification During Exergaming. In EuroVis 2016 - Posters. Groningen. The Eurographics Association, pages 25-27. (URL) (BibTeX)
7. Ji, Chengtao, van de Gronde, Jasper J. and Maurits, Natasha M. and Roerdink, Jos B. T. M. (2016) Tracking and Visualizing Dynamic Structures in Multichannel EEG Coherence Networks. In EuroVis 2016 - Posters.. The Eurographics Association, pages 28-30. (URL) (BibTeX)
8. Ji, Chengtao, van de Gronde, Jasper J. and Maurits, Natasha M. and Roerdink, Jos B. T. M. (2016) Exploration of Complex Dynamic Structures in Multichannel EEG Coherence Networks via Information Visualization Techniques. In CCS 2016 - Posters.. (BibTeX)
9. van de Gronde, Jasper J., Offringa, AndrĂ© R. and Roerdink, Jos B. T. M. (2016) Efficient and Robust Path Openings using the Scale-Invariant Rank Operator.. . Attach:pdf.gif Δ Δ (URL) (BibTeX)
10. Schubert, Herman, van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2016) Efficient Computation of Greyscale Path Openings.. . Attach:pdf.gif Δ Δ (URL) (BibTeX)
11. van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2016) Generalized Morphology using Sponges.. . Attach:pdf.gif Δ Δ (URL) (BibTeX)
12. van de Gronde, Jasper J. (2015) Beyond Scalar Morphology. PhD thesis. (URL) (BibTeX)
13. van de Gronde, Jasper J. (2015) Tensorial Orientation Scores. In Computer Analysis of Images and Patterns.. Springer International Publishing, pages 783-794. Attach:pdf.gif Δ Δ (URL) (BibTeX)
14. van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2015) Sponges for Generalized Morphology. In Mathematical Morphology and Its Applications to Signal and Image Processing. (Benediktsson, J\'on Atli, Chanussot, Jocelyn, Najman, Laurent and Talbot, Hugues, Eds.) Springer International Publishing, pages 351-362. Attach:pdf.gif Δ Δ (BibTeX)
15. van de Gronde, Jasper J., Lysenko, Mikola and Roerdink, Jos B. T. M. (2015) Path-Based Mathematical Morphology on Tensor Fields. In Visualization and Processing of Higher Order Descriptors for Multi-Valued Data. (Hotz, Ingrid and Schultz, Thomas, Eds.) Springer International Publishing, pages 109-127. (URL) (BibTeX)
16. van de Gronde, Jasper J., Schubert, Herman R. and Roerdink, Jos B. T. M. (2015) Fast Computation of Greyscale Path Openings. In Mathematical Morphology and Its Applications to Signal and Image Processing. (Benediktsson, J\'on Atli, Chanussot, Jocelyn, Najman, Laurent and Talbot, Hugues, Eds.) Springer International Publishing, pages 621-632. Attach:pdf.gif Δ Δ (URL) (BibTeX)
17. van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2014) Group-Invariant Colour Morphology Based on Frames.. . Attach:pdf.gif Δ Δ (URL) (BibTeX)
18. van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2014) Frames, the Loewner order and eigendecomposition for morphological operators on tensor fields.. . Attach:pdf.gif Δ Δ (URL) (BibTeX)
19. van de Gronde, Jasper J., Wilkinson, Michael H. F. and Roerdink, Jos B. T. M. (2013) Rotation-invariant morphological filtering of tensor fields using frames. In Poster session of the National ICT.OPEN (Eindhoven). nov. Attach:pdf.gif Δ Δ (BibTeX)
20. van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2013) Group-Invariant Frames for Colour Morphology. In ASCI.OPEN (Eindhoven). nov. (BibTeX)
21. van de Gronde, Jasper J. (2013) Web Graphics for Science. In HTML5 Developer Conference. oct. (URL) (BibTeX)
22. van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2013) Frames for Tensor Field Morphology. In Geometric Science of Information. (Frank Nielsen and Fr\'ed\'eric Barbaresco, Eds.) Springer Berlin Heidelberg, pages 527-534. Attach:pdf.gif Δ Δ (URL) (BibTeX)
23. van de Gronde, Jasper J. and Roerdink, Jos B. T. M. (2013) Group-Invariant Frames for Colour Morphology. In Mathematical Morphology and Its Applications to Signal and Image Processing. (Luengo Hendriks, Cris L., Borgefors, Gunilla and Strand, Robin, Eds.) Springer Berlin Heidelberg, pages 267-278. Attach:pdf.gif Δ Δ (URL) (BibTeX)
24. van de Gronde, Jasper J., Wilkinson, Michael H.F. and Roerdink, Jos B.T.M. (2012) Making computers see tensors using mathematical morphology. In Poster session of the National ICT.OPEN (Rotterdam). oct. Attach:pdf.gif Δ Δ (BibTeX)
25. A. R. Offringa and J. J. van~de~Gronde and J. B. T. M. Roerdink (2012) A morphological algorithm for improving radio-frequency interference detection.. . (BibTeX)
26. Jasper van de Gronde (2010) A High Quality Solver for Diffusion Curves. Master's thesis. Attach:pdf.gif Δ Δ (URL) (BibTeX)