Re: SVG2 CR - Catmull-Rom curve commands missing??

Very well said, in particular:
>Simply nobody needs such an empty version, maybe except the SVG working
group members to show existence.

I wonder if this "last call for CR review" thread has actually reached
anyone from the committee… and if so, what their response is?

On Mon, 12 Nov 2018 at 23:34, Dr. Olaf Hoffmann <>

> Doug Schepers:
> ...
> >
> > If the browser makers express willingness to implement it, I'd be
> > willing to write a spec just for that feature; that spec text could be
> > published on its own, or folded into a larger SVG2.1 spec, or whatever.
> > We'd also need tests for the feature; I could help with those, too,
> > though I'd like help on that.
> This would be a subset for the path d attribute value.
> I think, it is not a good idea to modify this somewhere else as in a major
> version of SVG as version 2.
> There are other requirements to extend the path syntax.
> This should be all in one major SVG version to avoid incompatibilities
> each new year of with each new subversion.
> Authors and users need reliability on such a core feature as the path d
> attribute for a long time.
> Else there would always be the question, do the users really see, what
> authors
> noted.
> Respectively there is a need to expose every version number of SVG to the
> users in user-agents older than the date of the SVG recommendation, a
> document
> refers to, else such new features in subversions or moduls become almost
> irrelevant an unusable for authors for a long time.
> >
> ...
> >
> > The upside to using Catmull-Rom curves is that they provide pretty
> > intuitive curves for a large range of variables (assuming you imply a
> > duplicate starting point and ending point to the formula, and have a
> > modest tension parameter), are fairly fast to compute (good for
> > rendering and animation performance), and are widely used in computer
> > graphics libraries; a downside is that the penultimate curve segment
> > does change its shape when you add another point, but perhaps that's
> > unavoidable.
> This is similar to the combination of Q and T commands.
> If one reduces the number of parameters, one does not have the complete
> control anymore - here the modifications are not completely local anymore.
> But of course, there are interpolation methods, which ensure, that a
> change of
> one point has only local influence on the curve to the next few given
> points.
> Doing this one still has to add some information, how to start and to end,
> respectively how to connect smoothly a closed subpath, what should be
> possible
> as well with this features to get a useful simplification for authors.
> If authors really want the complete control, they still can only use C
> commands with own calculations.
> Such smooth curves are mainly userful for authors searching for a fast and
> simple solution. They will surely accept, that they will not have the
> complete
> control, if they use such a set of commands.
> I think, for many authors it would be already ok to have something like
> the
> combination C and S, but without the additional control point (without
> tension
> parameter) to get smooth curves without calculation and without control or
> only with two control points (additional parameters) for the complete
> subpath.
> Charles Lamont:
> >I am another disappointed long-term want-to-user of curve fitting, but I
> >have thought for some time the WG is right to try to get SVG2 out as
> >soon as possible, containing whatever.
> >
> >Version 2 has already been far too long in the making, and
> >recommendation of the much more detailed and precise spec will
> >demonstrate that there is still a flicker of life in the project. Long
> >awaited, and very necessary enhancements can follow when implementers
> >see that some sort of progress is actually occuring.
> I think, it is the completely wrong message to authors, users and
> implementors
> to publish such a draft with almost no new features as a major version or
> as a
> recommendation at all.
> There is no need for this without all these features, once identified to
> be
> required for version 2.
> Those are the reason, why there was a need for version 2 at all.
> Without them this version is a document without any reason or purpose.
> Simply nobody needs such an empty version, maybe except the SVG working
> group
> members to show existence.
> Olaf

Received on Thursday, 22 November 2018 04:32:18 UTC