Iterate through all cells adjacent to a chunk.
Find the nearest point from a quadratic spline to this point (in terms of t,
the “distance along the curve” by which our spline is parameterized). Note
that if t < 0.0 or t >= 1.0, we probably shouldn’t be considered “on the
curve”… hopefully this works out okay and gives us what we want (a
river that extends outwards tangent to a quadratic curve, with width
configured by distance along the line).
Computes the position Vec2 of a SimChunk from an index, where the index was
generated by uniform_noise.
Computes the index of a Vec2 of a SimChunk from a position, where the index
is generated by uniform_noise. NOTE: Both components of idx should be
in-bounds!