Field around (cx, cz) for a settlement of radius metres; site adds terrain alignment.
The field direction at (x, z) closest to heading (hx, hz): one of ±major, ±minor.
Writes a unit vector into out.
Major-eigenvector angle (radians) at (x, z). The minor eigenvector is perpendicular to it.
A 2D street tensor field. TensorField.align turns a heading into the nearest field direction (major or minor eigenvector, either sign), which is how roads are steered.