Senses find how surfaces vary, and when they vary, and thereby find where they vary. Surfaces can be flat or curved. They can face to or away from a vantage point. Virtually all objects whose shapes can be perceived are combinations of surfaces. Surfaces form corners - concave or convex.
Convex corners can form occluding edges.
Rounded surfaces can offer occlusion too. A convex corner arises with some rounded surfaces, like teeth. If pictures can show edges of surfaces, they can show much of the visible environment. Klatzky et al - blind can do route tasks including short cuts. Klatzky et al - stress fixed procedures in tactile exploration.