In this tutorial we want to create a specific colormap for temperature data that are made available by the German Climate Computing Center (DKRZ) and the Max Planck Institute for Meteorology (MPI-M). The data include one timestep of the temperature at the height of 2m simulated with the icosahedral ICON model at a global resolution of 5km. We remapped the data from the unstructured model grid to aa regular grid with 4000-2000 grid points for easier use with different tools. At our data, the simulated 2m-temperature varies between around -63℃ and 52℃. Regionally, however, small temperature variations of the order of 0.1℃ might be critical for the analysis as, e.g., in the neighborhood of the freezing point at 0℃.

We didn't implement rendering features in the CCC-Tool so far. Therefore you can use the Testing section of the tool. We uploaded two data sections (North Pole and Africa) via white/black images into the real world data of the testing section. Click on the button "Test-Section" to get more information. Alternative: You can also use the software Paraview during this tutorial to create visualizations with the original data. To get more introduction, click on "Paraview".

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ParaView is an open-source, multi-platform data analysis and visualization application. For this option, you need an installed version of this software. If you don't have one, you can get the installation file here. Depending on the internet speed, the download will take about 3 Minutes.

Click on the folder image on the left side to download a .zip file with the temperature data. Unpack the archive file at a storage location of your choice. The unpacked folder include a NetCDF file (.nc) with the temperature data and a Paraview state file (.pvsm).

Open Paraview and drag and drop the .pvsm file into it. The popup window "Load State Options" will be displayed. Select the option "Search files under specific directory" for "Load State Data File Options". Set the data directory to the unpacked folder with the NetCDF file and accept it with "OK".

Fig. 1: Import state file to paraview.

After importing the state file, you can see in the pipeline browser next to the original "nwp_RB209_reg4k__T_2M_vis.nc" the "Calculator 1". Here we used the calculator feature to convert the Kelvin temperatures into centigrade. Click on the "closed eye" in the pipeline browser to show the element in the render window.

Fig. 2: Info to the imported state file. Compare "Point" rendering with "Surface" rendering.

The state file also set the option "Representation" from the default "Surface" to "Points". In Figure 2, you can see that the point rendering on the left side shows the correct colors of the colormapping. In contrast, the shader at the surface option (right side) influence the colors with lighting/shadows. Tip: You can rotate the rendering with the left mouse key. Here the surface rendering gives you a better image of the current location (Figure 3).

Fig. 3: Compare "Point" rendering with "Surface" rendering during the rotation.

Here a short tutorial on how to import colormaps from the CCC-Tool into Paraview. Activate the "Handle Twin Issue" option during the export in the CCC-Tool because Paraview cannot handle our notation of discontinuous transition points. If you forget this option, artifacts can occur in the colormapping. Select for the export format "XML" or "JSON".

Fig. 1: This figure shows the export settings for an import in Paraview.

In Paraview, open the colormap editor (Figure 2, Step 1). Here you can edit colors, the colormap range, and the colorspace for interpolation. With the "Choose present" option you can open a window to apply predefined or imported colormaps (Figure 2, Step 2).

Fig. 2: Open the colormap editor in Paraview.

Click at the "Import" button at the "Choose present" window (Figure 3. Step 1.) and select the exported CCC-Tool file. Exported colormaps from the CCC-Tool are always labeled with "ccc-tool_colormap_" + the colormap name. After the import, select "All" at the top (Figure 3. Step 2.) and scroll to the bottom. There you can find and select your colormap. At least click on "Apply".

Fig. 3: Import colormaps in Paraview.

We implemented this section to enable the testing of local and global attributes of scalar fields. Therefore, we offer different self-developed test-functions and predefined test-functions from other computer science and real-world data fields. We added two interesting data-sections via Black/White images to this testing section. Both with a resolution of 500p.

Fig. 1: Show the Testing Section.

You can reach the Testing section from the MyDesigns section or the Edit section (see Fig. 2). If you come from the MyDesigns section, the combo box at the top of the Testing section will be filled with the colormaps from the MyDesings section. Save every coming task of this tutorial as own colormap ('ctrl'+'d') and with this way, you can easily switch between colormaps and compare them. If you come from the Edit section, the Testing section will only show you the current state of the colormap in the Edit section.

Fig. 2: This figure shows how to reach the Testing Section.

If you have opened the Testing section, you will see the collection page. This page gives an overview of all testing functions of the CCC-Tool. Scroll down until you reach "3. Real World Data". The last two items of "3.2 Scientific Simulation" are the two data sections from the temperature field.

Fig. 3: This figure shows where you can find the two data sections of the temperature data.

Select an item on the collection page, and the "Interactive Testing" page with your selected test-function will be displayed. Here you can change options, add noise, save screenshots, compare the colormap with a grey scaled colormapping, and so on.

Fig. 4: This figure shows and screenshot of the "Interactive Testing" page.

For a better imagination, the "Interactive Testing" page also offers a 3D heightmap rendering of the test-function. Switch the radio button from "Pixel-Image" to "Triangle-Grid". At the top of the colormapping, some button will appear. There you can switch to the 3D rendering or show/hide the bounding-box/xyz-axis.

5. Fig.: This figure show a screenshot of the 3D hightmap rendering.