Seperate sub-routing for sub-boundary calculations

[vedadb]

For a sub-boundary calculation, a full grain-reconstruction is (in theory at least) unnecessary if large-angle grain-boundaries have already been reconstructed. It would make sense to create a subroutine for sub-grain boundary calculations not to have to pay this overhead, when studying effect of changing sub-grainboundary treshold angles.

E.g. grains.innerBoundary = calcSubBoundary(grains/ebsd, threshold);

Since vertices and edges (V,F) are already saved in the grain2d object (right?) The incidence matrices can be re-created and the sub-boundary can be re-calculated without paying price of voronoi tesselation.