Re: [Freetype-devel] Re: GSOC - Distance Fields

[Alexei Podtelezhnikov]

On Mon, Jun 15, 2020 at 11:03 AM Anuj Verma <anujv@iitbhilai.ac.in> wrote:
>
>
> > For linear segments, it will save more than 90% according to your
> > table. Then you will see that splitting Bezier curves is not such a
> > bad option. In general, Bezier curves are used in graphics because it
> > is easy to split and flatten them. I would be very surprised if
> > distance fields were different in this regard?
>
> Well, I'm not much familiar with the rendering part of bezier curve.

This primer is fun to read with many interactive demos:
https://pomax.github.io/bezierinfo/
The main thing to recognize is that splitting a Bezier at t=0.5 and
calculating the new set of control points for the halfs is lightning
fast. If you continue doing so, the segments very quickly converge to
almost straight (flat) segments.

> In distance fields I'm just concerned about finding the shortest distance as 
> accurate and as fast as possible.

Each split decreases deviation 4 times for a conic segment so that you
can reach a given accuracy of your distance field and use only
straight segments. The accuracy is defined by the grid resolution: it
won't be visible to a human eye if the approximation deviates from a
true curve by more than ~0.1 of the grid size.