Re: Rewrite Skyline code (issue 547980044 by address@hidden)

[hanwenn]

On 2020/04/19 22:35:39, dak wrote:
> On 2020/04/19 21:43:26, hanwenn wrote:
> > (this still needs some work, but the speedup might be worth an early
look)
> 
> * Buildings store Y coordinate of the left edge, rather than the
>   intercept at x==0.0.  This avoid excessive rounding problems when X
>   is large, and lets us compute building.height_at(x[LEFT]) cheaply.
> 
> Since intercept computation order depends on the execution of the
merge
> algorithm and we use floating point arithmetic rather than fixed
point, this
> would make results a lot less reproducible.

Hmm, OK. You say "a lot less". Did we measure this, and is this an
important characteristic of the code?

> I understand the sentiment and thought about it as well, but it would
only work
> if the _original_ coordinates were retained even after intersection
and
> additional intersections still worked based on the original
coordinates, making
> the merge order (mostly) irrelevant with regard to error propagation.

FWIW, I want to reduce the precision of the outlines anyway (because
they are way more detailed than necessary), and that is going introduce
much larger errors than propagated errors.


https://codereview.appspot.com/547980044/