Surprising behaviour from Geometry.is_point_in_polygon.
Check if each point in the polygon is "in" the polygon, using Geometry.is_point_in_polygon, which states
Returns true if point is inside polygon or if it's located exactly on polygon's boundary, otherwise returns false.
(bold emphasis mine)
Here we show basically the same polygon, with the yellow dots indicating the points for which the above function returns false, with each polygon a slightly larger version of the original.
(green dot is the first vertex, and blue dot is the last vertex)
Precision error?
Each vertex in the polygon should be in/on the polygon, so we should see yellow dots on every corner.
