Polygon.Clean (gb.clipper)
Function Clean ( [ Distance As Float ] ) As Polygon
Removes vertices:

that join colinear edges, or join edges that are almost colinear (such that if the vertex was moved no more than the specified distance the edges would be colinear).

that are within the specified distance of an adjacent vertex.

that are within the specified distance of a semiadjacent vertex together with their outlying vertices.
Vertices are semiadjacent when they are separated by a single (outlying) vertex.
The Distance parameter's default value is approximately √2 so that a vertex will be removed when adjacent or semiadjacent vertices having their corresponding X and Y coordinates differing by no more than 1 unit. (If the egdes are semiadjacent the outlying vertex will be removed too.)