Contours extracted from the island, with vertices in the source bitmap's world coordinates. Multiple contours appear when an island has holes (donut-shaped debris produces an outer contour plus one inner contour per hole). Closed contours come first.
Most-frequent material id across the island's cells. Used by the physics adapter to look up density / friction / restitution for the resulting dynamic body.
The connected component (cells + bounds) found by flood fill.
One detached connected component plus the data needed to convert it into a dynamic Box2D body.