Merging grains and multiscale tessellation

[MinMorsh]

Hello @rquey,

I generated the following 2D polycrystal using NEPER:

`neper -T -n 100 -domain "square(160,160)" -morpho "diameq:lognormal(3.2,0.01)+0.2*lognormal(16,2),1-sphericity:lognormal(0.1,0.02)" -dim 2 -group "diameq>9?1:2" -morphooptiini "weight:radeq,coo:packing" -o "test" -morphooptistop "eps<1e-4" '

I have 2 questions:

1. Is there a way in Neper to merge a subset of grains (e.g., all grains belonging to group 1 / the green grains) so that they are treated as a single connected grain or phase, rather than as multiple independent grains?

2. For visualization purposes only, is it possible to hide grain boundaries between grains belonging to the same group (e.g., between green grains), while still displaying boundaries involving the other grains (e.g., red–red and red–green boundaries)?

3. Is there any way (maybe multiscale tessellation) to create a thick (probably 1-2 nm) region between 2 neighboring grains? The goal is to explicitly represent grain boundaries as volumetric regions rather than zero-thickness interfaces. I understand NEPER cannot explicitly create finite thickness GBs, but is there any way to further divide each red grains in a way that I can take some grains from successive red grains and then merge them together later in other CAD softwares (like CUBIT)?

Thanks,
Minhaz