The AutoTerrain data structure contains the metadata used by the Auto Terrain system to render a sprite into an Auto Terrain sprite sheet. It is defined as:

CornerRadiuses : double[4]
InnerCornerRadiuses : double[4]
CutOffs : double[4]
InvertOuterCorners : bool
InvertInnerCorners : bool
TileWidth : int
TileHeight : int
Sides : Dict<int, AutoTerrainSide>
Overrides : Dict<int, AutoTerrainOverride>

Where AutoTerrainSide is defined as:

SpriteId : string?
Tile : TileMode
TileX : double
TileY : double
U : double
V : double
Rotation : double
IsActive : bool

The TileMode enum determines whether tiling, stretching or flipping of the sprite takes place. It is defined as:

enum TileMode
{
	Tile,
	Stretch,
	FlipX,
	FlipY,
	FlipXY,
}

And AutoTerrainOverride is defined as:

Background : AutoTerrainSide?
Foreground : AutoTerrainSide?
Decal : AutoTerrainSide?