On Sat, Aug 29, 2020 at 9:12 PM Anuj Verma <an...@iitbhilai.ac.in> wrote:

> Hello All,
>
> I have written the final report for my project.
>
> You can check it out here:
> https://gitlab.com/-/snippets/2007070
>

Thank you Anuj. I really enjoyed observing your work this summer, even
though I didn't get to contribute more review. I promised you a proof and
here it is:

> Lemma: if the closest point on curve [0,1] is to the endpoint at t=1 and
the cubic equation has no real root at t=1, the cubic equation must have at
least one real root at some t > 1.
> Similarly, if the closest point on curve [0,1] is to the endpoint at t=0
and the cubic equation has no real root at t=0, the cubic equation must
have at least one real root at some t < 0.
>
> As such, you just need to compute all real roots, clamp them to [0,1] and
remove duplicates.

Here's the proof for the first case: Consider the derivative of the
distance, called "the function" from here on. It's a continuous function.
At t=1 the function is a negative number because of the assumptions. When t
tends towards +infinity, the function approaches +infinity. As such, there
exist t > 1 where the function is zero.

Cheers,
b

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