Tips

December 2002 - Issue 15
E-Newsletter for Tecplot Users

03.  TECPLOT TIPS - USING THE EXTRUDE ADD-ON TO GENERATE VOLUME DATA FROM 3-D SURFACES

In the July issue we discussed making projection plots from 3-D surface data. In this issue we'll extrude our data from 3-D surfaces to 3-D volumes.

Generating 3-D volumes directly from topographical data is convenient if you want to study subsurface or geophysical properties. Tecplot 9.2 contains several new mesh generation tools. In the following example we will use the Extrude add-on.

The Extrude Add-On
Extrude is included in the newest release of Tecplot . This add-on extrapolates a zone in one direction. For example, if you have a 1-D zone (a line) Extrude can project that line into a surface along any axis. Similarly if you start with a 2- or 3-D surface Extrude allows you to project the surface into a 3-D volume.

A few notes:
1. Extrude requires that you have at least three variables.
2. Extrude works with both structured and unstructured grids.
3. Unstructured grids extrude in a series of similar planes.
4. Initially extruded zones appear in 3-D frame mode with only the new zone active.

Example
Click here to download a Windows Media Video (extrude.wmv 10,094KB) of this example.

In the following example we will create a 3-D volume from topographical data and use bore-hole data to determine sand and silt levels.

The topographical data represents the surface of the ground where the borehole measurements were taken. The purpose of extruding is to create a volume zone that extends to the depth of the boreholes.

Click here to download the example data (topo.plt — 259 KB) and follow along.

1. From the File menu, select Load Data File(s) and with the Load Data File menu select topo.plt.

2. On the sidebar, switch to 3D frame mode and click on Contour. Select V4: Content as your Current Contour Variable.

3. From the Tools menu, select Extrude.
To make Extrude appear in the drop down, open the tecplot.add file (found in the TEC90 folder) with a text editor. Make Extrude active by removing the # comment character from the beginning of that line. Extrude will now appear in your Tools menu.

4. On the Extrude Options dialog, select Rectangular zone as the Source Zone and Alt as the Z-Variable. Change Extrusion Distance to -6. Click OK.

   
5. From the Axis menu, select 3D Axis Reset.
Click off Mesh from the sidebar.

Resulting image from steps 1 through 5.

You can see how the original topographical data has been extruded down. The next step is to read in the borehole (well) data. By interpolating from this measured data to the extruded zone of the region, we can determine the amount of rock, sand and silt at different levels.

1. From the File menu select Load Data File(s) and select Add to current data set.

2. Select well_test_data2.dat Click here to download well_test_data2.txt
(2 KB) .
This data set contains XYZ locations and whether rock, sand or silt is present. Values of 1, 5 and 10 were assigned to the rock, sand and silt.

3. From the Data menu select Interpolate /Inverse- Distance.

4. From the Inverse-Distance Interpolation dialog select 3: Zone 001 as the Source Zone. Select 2: 3D extruded zone as the Destination Zone. Click Compute.
This takes our bore-hole data (ZONE 001) and interpolates it using 3D extruded zone as the Destination Zone.

5. From the Field menu select Contour/Contour Levels.

6. On the Contour Levels dialog select Reset Levels.

7. Reset the Number of Levels to 15. Click OK.
 

Resulting image from steps 1 thru 7.

To isolate our sand and silt levels we need to identify iso-surfaces for each.

1. From the sidebar click Shade and Translucency. Uncheck the Contour toggle.

2. From the Field menu select 3D Iso-Surface Details.

3. On the 3D Iso-Surface Details dialog select the options displayed in figure shown to the right.

Resulting image from steps 1 thru 3.

The last step in the process is to turn on the bore data in our volume.

1. From the sidebar click Scatter.

2. From the sidebar click Plot Attributes. This opens the Specify Plot Attributes dialog..

3. From the Specify Plot Attributes dialog select the Scatter tab.
Turn Zone Show to Yes for Zones 2 and 3.

4. Turn off Scat Show for 3D extruded zone.

5. Select ZONE 001 and edit the scatter properties as follows:
* Outline = Black.
* Fill = Yes.
* Fill Color = Multi.

The final plot. Presentation enhancements were made by:

• Extracting the iso-surfaces.
• Setting Shade colors for the iso-surfaces.
• Setting different levels of translucency for the iso-surfaces.
• Setting Translucency on the 3D extruded zone to 65%.
• Moving the 3D Light Source.
• Changing Lighting effects to Gouraud.
• Exporting a PNG image.

This is just one the many uses of Extrude. These steps could be applied to any number of system and data types.

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