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Issue with ConstructSurfaceModifier

Greetings!

I have a python script that selects a subset of particles in a system and creates a surface mesh using only that subset. It loops over all frames of a trajectory file generated with Lammps. It works just fine with two trajectory files, but it exits with the following error message with a third one:

Data pipeline evaluation failed: Modifier 'Construct surface mesh' reported: Cannot construct mesh for this input dataset. Adjacent cell face not found.

If I use the GUI, I can see the frame at which ovitos complains. If I use all particles in the system to create the surface mesh, it works (but that is not what I need). If I check the box to use only the selected input particles, it generates the error message. I have checked the trajectory file and everything looks fine.

I would appreciate any suggestions!

Hi Felipe,

For certain inputs, the algorithm may not be able to construct a valid surface and it will stop with the error message you mentioned. If you activate the 'Use only selected particles' option, the set of particles that are actually passed to the surface construction algorithm will be prefiltered by OVITO. In other words, from the algorithms point of view it is as if you had deleted all unselected particles first. You can verify this by inserting an Invert Selection modifier and a Delete Selected modifier into the pipeline prior to the Construct Surface modifier (with the 'Use only selected particles' option turned off).

The important question is: Is there any way to avoid the error message and make the algorithm produce a valid surface for the given input? Sometimes there is. For example, it can help to use the Replicate modifier to extend the size of the system (if it is periodic) prior to the surface construction.

In order to help you with this, it would be good if you could send me the problematic particle dataset. I can try to find out more about why the surface construction fails in this particular case.

-Alex