What are CSG errors, why am I getting them, and how can I resolve them?

Symptoms:

When trying to create a surface in a Geological Model, I get an error message stating that I have encountered a CSG error. Sometimes this popup contains coordinates, but sometimes my processing panel just errors out.

OR

I am trying to use an Output volume from one model as a boundary for another model in Leapfrog, and the volume of interest is not available to be selected as a boundary.

Resolution:

CSG stands for Constructive Solid Geometry. Sometimes, when processing a model, Leapfrog will display an error message indicating a CSG error has occurred, preventing a volume from being created, and sometimes Leapfrog will still create the volume, but it will not be valid, or usable as input into another model.

You can determine if a volume is valid by right-clicking it and selecting Properties. A volume is valid if it is Closed, Consistent (no self-intersections) and Manifold (can tell inside from outside).

CSG errors can be challenging to resolve as they typically occur in highly complex models. If you have encountered a CSG error, you can try the following to resolve it.

1. Turn Adaptive resolution on or off (i.e. whichever one it currently isn't).
2. Change the Resolution of the surface by a small amount. Often +/- 0.1-0.5 is enough.
3. Try to use a consistent Resolution throughout the model, as much as possible.
4. Enable Merged output volumes (double-click the Geological Model, in the General tab).
5. Change the Snap to data option (or increase the Maximum snap distance if it's enabled) in the model's General tab.
6. Ensure there are no duplicate data points used as values, extents, or intervals.
7. Move one of the inputs by a small amount. Often moving a drillhole by 5cm will fix the issue, and not materially affect the precision of the model.

If the CSG error was manifesting as an invalid output volume, check the volume’s Properties after each potential resolution to see if the volume has become closed, consistent and manifold.

Root Cause:

CSG errors are caused when Leapfrog cannot, for some reason, compute a closed, consistent, manifold mesh. CSG errors happen on occasion with complex inputs, or if you are building a model from inputs with different resolutions (e.g. a mesh with a resolution of 50 used inside a model with a resolution of 20).

If you've tried the each of these suggestions and still haven't been able to resolve the CSG error, please contact your local Seequent team for further assistance.