How do I assign a Null or NoData value to a lattice above an irregular topography surface in Voxler?

Use a Math module with a Boolean IF function to remove data from (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.

Note: The GRD file must be imported as a uniform lattice.

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 Property Manager.

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.
Updated January 7, 2019
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