How do I blank a lattice above an irregular topography surface? Use a Math module with a Boolean IF function to blank the area above a surface. Attach the 3D lattice as input "A" and a GRD file with the topography as input "B" to the input of the Math module. Use an IF function with the following syntax: IF Z > B, 0, A Or Z > B? 0:A With a GRD file, the elevation data is imported as component 1. Both statements say to set output value to 0 if the Z value is greater than the elevation data in the GRD file (or "B"). If the Z value is less than the elevation value in B, use the data value in A. In this example, a value of 0 is used, but any value less than the Z minimum of the data can be used. Connect a VolRender module to the output of the Math module, and set the 0 values to be transparent in the ColorMap editor accessed via the ellipsis button [...] to the right of the ColorMap example in the VolRender Properties window. Blank a lattice above a GRD surface. The same principle can be applied to blanking to the right of an X value in a BLN file. Remove the BLN header, save to a DAT file in Surfer, and grid the DAT file using the X 

column for the Z value. In Voxler, attach the Gridder module and GRD file to a Math module as above, and change the reference in the Math equation from Z to X: X > B? 0 : A Blank a lattice to the right of an X value in a BLN file. How can I load a Surfer GRD and visualize it without the blanked nodes? To load and visualize a Surfer GRD file, load the GRD file and display it as a HeightField. To turn off the display of the blanked nodes, edit the ColorMap so the opacity of the data minimum is set to 0: 1. Go to File | Load Data 2. Select the GRD file and click Open 3. In the Network window, right click over the data module and go to Graphics Output | HeightField to attach a HeightField module.The blanked nodes will be shown as a flat plane at the Z minimum of the GRD data (below in purple). 4. In the Properties window, click on the ellipsis (...) button to the right of the ColorMap option. 5. In the ColorMap Editor, double click at the left end of the top spectrum to add a new node close to the one at the left end. 

6. Select the node at the left end and change the Opacity (upper right) to 0. 7. Click Close and the flat area of the blanked nodes will be removed.