If the last point of a line is the same as the first point when using the LineBuilder transformer, FME will automatically create a polygon.

• A. False
• B. True
• C. Not sure
• D. Only if AreaBuilder is used.

Answer: (B)

A closed ring is what makes a polygon. When the last point of a line matches the first, the line forms a closed loop, which defines the boundary of a polygon. The LineBuilder in FME recognizes this and outputs polygon geometry for that feature automatically, without needing an additional tool to convert it.

So if you provide a sequence like A–B–C–A, you’ll get a polygon representing that loop. If the line isn’t closed (first point different from last), you’ll still get a line, not a polygon. AreaBuilder isn’t required to make this conversion.