Overlapping convex space is defined by reference to the surface of each block, each of which defines its maximal convex field. Their fields will inevitably overlap, and where they do, the area of overlap will itself form a smaller convex element from which both overlapping convex spaces will be fully visible, that is, will be convex, although these spaces are not convex to each other.
Overlapping convex space
Hillier, B. (1996, 2007), Space is the Machine: A Configurational Theory of Architecture. Space Syntax: London, UK. pp.93