odf file 66 is opened and all the region data is stored in an internal region data structure this data is used subsequently to perform the required steps then each down facing region is considered and support lines and hatch lines are generated the support lines are generated exactly under the perimeter of the region and then two sets of hatch lines are generated one set is parallel to the x axis and the other is parallel to the y axis the distance between the two parallel hatch lines is equal to a value specified for the line spacing parameter hatch lines are always generated parallel to the x and y axes initially the hatch lines parallel to the x axis are generated so that the distance between two parallel consecutive hatch lines is equal to the line spacing each hatch line is then trimmed at the point where it intersects the support lines for that region additional vertices are introduced in between the end points of each line such that the distance between consecutive vertices is equal to the strand spacing the hatch lines parallel to the x axis are generated and the hatch lines parallel to the y axis are then generated it should be noted that when generating the support lines the original vertices that defined the perimeter of the region are used to give the basic support lines additional vertices are introduced in between the original vertices so that the distance between consecutive vertices is equal to what is known as the strand spacing parameter however if the original vertices are less than the strand spacing then no vertices are introduced between the original vertices a filtering process in the algorithm is employed at this point for stl models or parts 11 that are finely tessellated.