Interactive visualization of Elmer/Ice results in ParaView (v.5.8.0)

After the run has finished, you will find the output files in the mesh-directory. The case is set up in such a way, that output is written into unstructured VTK files, i.e. files with suffix .vtu, each for one task that has been run. That means, in case of e.g. 128 MPI tasks, one is left with 128 VTU files in this directory, each containing the result for its partition. For the example given above, the name of these files is:

There is also a “master” file for these with the suffix .pvtu, i.e.

Download and install ParaView here. In This tutorial we use v5.8.0

Upon launching ParaView, you have to find the PVTU file (usually the last one in the long list), click on it, and load it (press OK)

Open

Do not despair, if your screen remains blank. You will see a green button Apply on the left menu. Click on it.

Open

Then ParaView will start loading the (quite large set of) files. So, be patient. For some reason, the first display will be a variable called glaciated (which is in latest versions of the test a constant unity field).

We just want to render surface properties of a (very flat) 3D mesh. To ease the computing in further processing, we can apply a filter called Threshold, which can either be accessed by the menu Filter-> Alphabetical, or by the symbol

In the menu for Threshold, apply the settings as shown in the screenshot:

• Use GeometryIDs under Scalars (to apply the threshold)

• Check Minimum as well as Maximum to be 103.

• Finally, press Apply

To explain: Boundary numbering as written by Elmer starts at 101 and 103 is the third (and last) boundary, constituting the upper free surface of the ice-sheet. The gain in displaying only this one is that (instead of a three-dimensional visualization) we switched to two-dimensions and will thereby make the rendering easier. After pressing Apply, we should get the same picture as before (but just the surface).

In order to change the output to velocity, change the displayed variable in the tools bar from glaciated to velocity (leave default additional setting Magnitude)

You will end up with a picture like that …

… which might be disappointing, as it reflects the fact that most of the Greenland ice sheet (compared to the here computed max. 40 km/a outlet velocities) basically is stagnant.

In order to actually better see what is going on at the fast outlet glaciers and simultaneously also inland, we have to switch to logarithmic scale. First scale the range by pressing

to these values

Logarithmic scaling is included the settings for the colour scale

Toggle Use log scale when mapping data to colors . You should end up with a rendering like this one:

Despite earlier suggestions, we ask to stick with the default blue-to-red ParaView coloring as shown above. Close the Color Map Editor window by clicking the cross in the upper right corner (see blue circle in previous
screenshot).

In order to get a little bit of shading, one could scale the vertical coordinate by a factor 3 – this is done in the Transforming panel of the Threshold1 filter object.

After doing so, the screen should look like:

The final step then is to take a screenshot of the scene. This is achieved by accessing the File menu and click the menu entry Save Screenshot therein. You will be provided with a panel that will provide you to choose where to save the file. Choose output format to be JPG. Choose a file name that consists of the name of your group and the date of the screenshot (similar to the example given below). Press OK and you (by default, if you did not choose to save elsewhere) will find the JPG in the same directory you launched ParaView from. After having filled in the name press OK.

Then a new window with Options for the screenshot pops up. It is OK to go with the defaults (default resolution of the rendered picture will depend on the resolution of your screen and the ParaView window therein).  

A further hint: If you want to keep this rendering scene setup for later, you can save it under File ->  Save State …  and then reload it later from File ->  Load State …  .