Special Konversatorium on Friday, April 25, 2014 - 10:30

Date: 
Friday, April 25, 2014 - 10:30
Location: 
Seminar room E186 (Favoritenstraße 9, Stiege 1, 5th floor)

Color and Perception of transparent surfaces and modifications to opacity in Paraview’s volume rendering (Guest Talk)

Speaker: 
Nicholas Waldin
Duration: 
30 + 15
Responsible: 
IV
This talk is a sponsored talk of the Colloquy Cycle

There are two parts to this talk. The first gives an overview of my Master’s thesis, which is about visualizing stream surfaces. The second is about modifications and additions to Paraview that I did as part of my internship at the Swiss National Supercomputing Center.

Stream surfaces are used to visualize snapshots in time of fluid flow. However, as useful as they are, they also have significant problems. In particular, humans have a difficult time understanding these surfaces and often make errors.

The thesis investigated the hypothesis that artificial coloring can help viewers perceive stream surfaces.  I present three algorithms for deciding on and placing colors based on a surface’s curvature or the use of simulated viewpoints. I will also discuss a user study that I designed and carried out that tested how users perceive images of surfaces that were created with these algorithms.

My work with Paraview involved improving the control of opacity in volume rendering. When using transfer functions to determine opacity in volume rendering, it can be difficult to get a good visualization with just one transfer function. Therefore, it can be useful to use two different transfer functions based on different aspects of the data, such as scalar and gradient values. I will describe and demonstrate a modification to Paraview’s GUI interface that allows users to use two different transfer functions and a new feature in Paraview that allows users to specify a two dimensional transfer function.

Additional Files: 
AttachmentSize
PDF icon Waldin.pdf36.1 KB

Visualizing the Long-term Behavior of 3D Fluid Flows (Introduction Talk)

Speaker: 
Andrea Brambilla (UiB, Norwegen)
Duration: 
30 + 15
Responsible: 
IV

The study of the long-term behavior of 3D fluid flows can provide useful insights into transport phenomena, which are of central importance in many fields, such as medicine and engineering.  Such a study is normally based on the integration of the flow field.  The resulting integral structures are indeed highly expressive, but their direct visualization often suffers from cluttering and occlusion issues. 

In this talk I will present my recent (and future) work addressing this problem.  Three projects will be covered: (1) A seeding strategy for families of integral surfaces, which captures the predominant aspects of the long-term flow behavior.  (2) A technique for easing the investigation and comparison of surface families, based on a 2D reformation process.  (3) The work I am carrying out here at the TU, aimed at quantifying transport phenomena and depicting them using Sankey diagrams.