Describe workflow for labeling areas in an *.stl file of the heart (e.g. in Blender)

Situation: I have a 3D surface model of a heart in *.stl format. What I need: I need to label areas on the heart surface and get the IDs of the nodes in these areas (regions of interest). For inspiration, see [1], [2], [3]. Requirements: The areas should not overlap. Together, the areas should cover the heart inner and outer surface completely. ######### Task: - Download a random *.stl file, e.g. [4]. - Make a simple PDF that describes how to perform the following steps in any free software you recommend for this purpose (e.g. Blender): 1. Select areas on the surface of the *.stl file that do not overlap, but that cover the surface completely. 2. Produce a list of the node IDs of these areas. ######### Thanks for your help! Best, Walther ### [1] [login to view URL] [2] [login to view URL] [3] [login to view URL] [4] [login to view URL]