On Thu, Jul 15, 2010 at 6:08 PM, Dave Crossland <dave@...1555...> wrote:
Hi,
Over on the www-svg@...157... list, there has been some discussion about Catull-Rom splines, triggered by http://schepers.cc/?p=243 and http://schepers.cc/svg/path/dotty.svg :)
These CR curves look exactly like Inkscape's "auto smooth" node type; could someone confirm this? :)
Maybe it's not exact but very similar - I made a doodle in dotty.svg, then retraced it in Inkscape and made all nodes autosmooth, and got a very similar outline.
But regardless of exactness, I think you are spot on in that auto-smooth nodes can be very workable compromise that can be made part of SVG core without burdening implementers too much.
Inkscape's auto-smooth nodes are simply beziers with some additional constraints on Bezier handles. These constraints, enforced during editing, make them behave in a very intuitive and useful way. Some on this list even commented that they may be more useful in practice than Spiros. And for the purposes of SVG standardization, they are much less burdensome: no Bezier fallback is necessary - they are already Beziers; the attribute indicating the auto-smoothness can be entirely ignored by renderers - it's only for software that can actually edit the path; and even then it is very easy to implement and involves no scary math that threatens to explode into infinities.