What is visual structure?
Visual structure is the way the physical structure is perceived of – in this case – homes and buildings and their immediate surroundings such as gardens and adjoining (play)grounds. Architectural design is at the same time concerned with physical structure (the arrangement of spatial elements of a building) and with the impression of it. The latter concern is driven by a number of motives such as beauty and functionality. In designing for autistic people there is a more than usual emphasis on the understanding of the spaces and their functions (their ‘readability’).
More about this here.