Refer to the attached example script, which illustrates one approach to do this. The script is very similar to creating geometry using "geometryFromMesh" in conjunction with "alphaShape". For more information, please run the below command in the MATLAB R2018b command window to get the release specific documentation which discusses the same:
web(fullfile(docroot, 'pde/ug/pde.pdemodel.geometryfrommesh.html#buvmj0q-1'))
The major differences are:
1. We need to define the entire geometry and its regions separately using "alphaShape".
2. We need to use "inShape" to get the mapping "ElementIDToRegionID" and pass it as a fourth parameter to "geometryFromMesh".
3. We need to use "alphaTriangulation" command instead of "boundaryFacets, as the "boundaryFacets" command will simply give one contiguous region.
Please follow the below link to search for the required information regarding the current release:
