 Intuitively, adding an edge of fixed length to a graph reduces its number of degrees of freedom by one, so the 2"n" − 3 edges in a Laman graph reduce the 2"n" degrees of freedom of the initial point placement to the three degrees of freedom of a rigid graph.However, not every graph with 2"n" − 3 edges is rigid; the condition in the definition of a Laman graph that no subgraph can have too many edges ensures that each edge contributes to reducing the overall number of degrees of freedom, and is not wasted within a subgraph that is already itself rigid due to its other edges.A pointed pseudotriangulation is a planar straight-line drawing of a graph, with the properties that the outer face is convex, that every bounded face is a pseudotriangle, a polygon with only three convex vertices, and that the edges incident to every vertex span an angle of less than 180 degrees.