# Name of “reverse convex hull”

I have a set of Points representing building footprints (black in the image below). I also have Points (building address Points) that I know lie inside the building footprints (green).

I'm searching for the name of a reverse convex hull analysis(?). Imagine blowing up a balloon starting at green Points.

I will then use the results to give each black Point an address (which is stored in the green Point)

• Could you instead find the distance from the green point to the further black point, then construct a circle with bigger radius than that, then apply regular convex hull analysis? – Ian Miller Nov 30 '16 at 13:08
• I dont Think that will work since the convex hull will possibly include black Points from nearby other Buildings. – BERA Nov 30 '16 at 13:11
• Can you have concave building interiors? You mention convex hulls but I can think of many buildings which are concave on the inside. – Ian Miller Nov 30 '16 at 13:15
• Yes it is possible. – BERA Nov 30 '16 at 13:20
• But if the interior doesn't have to be convex, your hull is not well-defined. In your example, the buildings might as well be joined at the bottom to form a "U". – Dominik Nov 30 '16 at 13:27