Reply To: Extract Lattice data
w.r.t. geometry renames:
All material numbers being set to zero is simply the default. This makes sense as zero cells are considered as inactive cells for which no processing is done.
More complex geometry setups are commonly created using indicator functors. OpenLB provides both a library of indicators for various geometric primitives as well as a STLReader indicator for importing STL data. All of these can be used in rename calls to set material numbers. You can check out e.g. the cylinder(2,3)d examples for basic examples of this. The User guide also contains further explanations.