Before revision:  The key to Polylidar's speed, and the main contribution of this paper, is in efficiently transforming each triangular mesh into a concave polygon . This paper describes Polylidar and provides benchmarks to comparatively evaluate its speed and accuracy.
After revision:  Finally each region is converted to a polygon through a novel boundary following method which accounts for holes. Real-world and synthetic benchmarks are presented to comparatively evaluate its speed and accuracy.