Kenneth <kdw### [at] earthlinknet> wrote:
> Yet, from the user's standpoint, the docs still leave out a few details that
> would be useful (to avoid 'mysterious behavior'): What exactly *is* meant by a
> 'low' value for Foresight;

  The value should be small enough so that such a section of the spline of
that length has no significant curvature. (The more curvature there is in
the section of the spline between the two sample points, the less accurate
the approximated direction vector will be.)

> and what's the lowest value that we shouldn't go
> below. In light of all that's been said, I think the only thing that *is*
> needed is a caveat in the docs--perhaps in one of those yellow boxes--something
> like this:
> "Since it's mathematically difficult to determine EXACT alignment using
> Foresight, a recommended lowest value is *-----*."

  The problem is that there's not really a good lowest (or largest)
recommended value because it depends on the spline itself.

  You can't just say "a value of 1e-10 is recommended" because then if
your spline control points are at huge distances, you will get significant
rounding errors. On the other hand you can't say "a value of 0.1 is
recommended" because if your spline control points use very small values,
you will get significant approximation errors (because the curvature of
the spline will probably be very significant on those distances).

  "A value of 1/100 of the minimum distance between two consecutive control
points" could be closer to working, but could still depend on the spline
(if the curvature is really pronounced at some location, even that value
might not be accurate enough).

-- 
                                                          - Warp

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