Rounded corner points for the path tool

[Cale Gibbard]

It would be nice to have a new path node type for a rounded corner, essentially generalising the rounded corners currently available in the polygon tool. It would behave the same way as a corner point does presently, except it would additionally be parametrised by a radius R less than the distance to the next control point in the path (or potentially two radii, one for each side). The effect would be to take the curve as it would be if the point were an ordinary corner point, and cut it at two points which are that distance from the corner point, then to insert a new segment in between those with tangents on the side of the rounded corner point having the same direction as the curve, but with magnitude equal to (4/3)(sqrt(2)-1) times the radius R, which ensures that a good approximation to a circular arc is obtained in the case that the corner is square. On the other side of the cut, the tangents would be preserved, so as to leave the curve the same as an unrounded corner outside the given radius.

Please see the attached diagram, as the above description may otherwise be hard to follow.

It would be rather nice to have this feature, as while it's certainly possible to construct and splice in rounded corners in paths, it's a tedious task, and the corners usually must be reconstructed if the path changes, say, if the angle of the corner needs to change. This would avoid that hassle.

[sas (sas-sas)]

The proposed fillet tool does this sort of thing: https://blueprints.launchpad.net/inkscape/+spec/fillet-tool

[Cale Gibbard (cgibbard)]

It's good to see that someone else has had this sort of idea. :) I
would be happiest if the corners remained editable even after
modification in this way, with the radius and corner effect type
stored in the node, (and of course the results cached until the curve
is edited in a way which involves that node, to avoid needless
recomputation).

One difference between the rounding method I described and the fillet
method described there is that while the fillet is certain to fill the
gap with a nice circular arc (which is certainly something I'd quite
often want), the portion of the curve influenced by the effect isn't
determined by the radius alone, but by the entire shape of the curve,
which would make it a bit less stable under editing operations
(solutions can easily disappear or reappear, and the curve will "pop")
. Still, it would certainly be enough to keep me happy. :)

On 16/03/2008, sas <email address hidden> wrote:
> The proposed fillet tool does this sort of thing:
> https://blueprints.launchpad.net/inkscape/+spec/fillet-tool
>
>
> --
> Rounded corner points for the path tool
> https://bugs.launchpad.net/bugs/202751
> You received this bug notification because you are a direct subscriber
> of the bug.
>
> Status in Inkscape: A Vector Drawing Tool: New
>
> Bug description:
> It would be nice to have a new path node type for a rounded corner, essentially generalising the rounded corners currently available in the polygon tool. It would behave the same way as a corner point does presently, except it would additionally be parametrised by a radius R less than the distance to the next control point in the path (or potentially two radii, one for each side). The effect would be to take the curve as it would be if the point were an ordinary corner point, and cut it at two points which are that distance from the corner point, then to insert a new segment in between those with tangents on the side of the rounded corner point having the same direction as the curve, but with magnitude equal to (4/3)(sqrt(2)-1) times the radius R, which ensures that a good approximation to a circular arc is obtained in the case that the corner is square. On the other side of the cut, the tangents would be preserved, so as to leave the curve the same as an unrounded corner outside the given radius.
>
> Please see the attached diagram, as the above description may otherwise be hard to follow.
>
> It would be rather nice to have this feature, as while it's certainly possible to construct and splice in rounded corners in paths, it's a tedious task, and the corners usually must be reconstructed if the path changes, say, if the angle of the corner needs to change. This would avoid that hassle.
>