Hello Alexei, Werner,
>> I meant it all along but perhaps it is hard to do it on the fly. Ther
>> rules seem to be as follows:
>>
>> 1) Both outside (both positive), choose a smaller value
>> 2) Both inside (both negative), choose a smaller value as in (-5 < -4)
>> not by absolute value
>> 3) one inside one outside, choose a smaller value as in (-3 < 2) not
>> by absolute value
>>
>> I.e. always choose a smaller value combining two contours so it seems
>
> Along with this we probably also need to find the resultant vector in case
> two distances are non infinite at a same point (i.e. the distance values
are
> less than spread), that we can find the distance to the corner even tho
> there is no actual corner in some glyphs.
I've added the overlapping support according to your algorithm, however I
have
modified the rule as follows:
-> Generate SDF for each contour in a separate bitmap.
-> for combining all the SDF to one use the below rule:
-> for each pixel/grid point:
c = for all clockwise contours find the largest signed value.
ac = for all counter-clockwise contours find the smallest
signed value.
final_value = smallest signed value of `c' and `ac'.
It works well for all of the glyphs that I checked apart from glyphs with
self
intersecting contours, because they can't be separated into different
bitmaps. To
handle self intersecting contours I think there is only one way and that is
to remove
the overlaps.
[
Werner,
Are you still interested in adding API to remove overlaps? I watched the
skia code
and the video on how it's done in skia. I think it's doable, the only
tricky part that I
think is to find the intersecting point of contours, because they use a
4th degree
polynomial to find the intersections.
If you're still interested in adding the API, I can start reading more
about it after GSoC
and then add it.
]
I have updated the demo to include the new algorithm to handle overlaps. I
have also
disabled all the optimization modes except the subdivision optimization (it
will be the
default one from now on until I find something even faster). Here is the
link:
https://github.com/preversewharf45/ft2sdf-demo, for help screen press '?'
or F1. There is
a `CascadiaCode.ttf' font which is full of overlaps, so that you can check
how the new
algorithm performs.
And now that GSoC is almost over, I will fix the compiler warnings first.
And then I will
write a brief description of how both `sdf' and `bsdf' renderers work in
the source files.
And finally I will create a new branch and add the code there. If there is
anything else
please do let me know.
Thanks,
Anuj
