Hello Alexei,
> I actually think that it is faster
>
> foreach line
> for proximal gridpoints
> do work
>
> where proximal is at most 8 grid units away. The rest is truncated
> (clamped) at 8. I am choosing 8 because this is probably enough (or
> not).
I tried this method, and yes it is very (probably a lot) faster than checking all the
grid points. I did not check the performance but now I can generate 512 pixel size
glyphs within a click. However there are a few issues:
* First, subdividing creates wrong results. I did not try subdividing bezier curves. For
start I simply divided the line segments into 8 segments and I generated SDF in the 8x8
neighborhood of those segments, but it results in wrong distances at some points. I don't
know the exact reason for this so I will try to find it out.
> The sign is tentative and flips on
> updating the grid depending if it is to the right or to the left of
> the line.
* It is correct to determine the sign this way, but it only determines the sign of the
pixels that we are actually checking. There are still points left whose sign is to
be determined. We can clamp them to 8, but still the sign has to be determined. I think
Lastly, instead of checking the 8x8 neighborhood of the line segments, I calculated the
bounding box of the line, increased it by 8 in the x and y direction and used that to
We can even align the bounding box along the line and create a pretty tight space. I
think it is worth giving it a try as well.
Anuj
