NormalDirection
NormalDirection =
"flat"|"up"|"north"|"down"|"south"|"left"|"west"|"right"|"east"|"up-left"|"north-west"|"up-right"|"north-east"|"down-left"|"south-west"|"down-right"|"south-east"|number
Defined in: packages/normals/src/descriptor.ts:32
Screen-relative direction the surface normal’s XY component points.
Mental model: imagine the baked normal as an arrow. NormalDirection
is the screen-space direction that arrow tilts toward — equivalently,
the direction the tile’s visible face is “pointing.” For a wall at
the top of the map (visible face toward the camera below), that’s
'south' / 'down'.
Cardinal and compass aliases are equivalent; the canonical form in the codebase is NSEW. Numbers are interpreted as radians in standard math convention (0 = +X / right, CCW positive).