Vertex figure (InstanceTopic, 3)
From Higher Dimensions Database
The vertex figure of an n-dimensional shape is the n-1-dimensional shape which is projected by the original shape when it is projected with the vertex normal and camera normal being equal. The vertex figure of a shape is only defined for uniform shapes, but vertex figures can be defined for specified vertices of any shape. Alternatively, the vertex figure for every vertex in a shape can be found and collected in a set to be associated with the original shape.