[svgwg] Mesh Patch in SVG2 is not C1 smooth at edge

wada314 has just created a new issue for https://github.com/w3c/svgwg:

== Mesh Patch in SVG2 is not C1 smooth at edge ==
Hello everyone,
Sorry if this is already discussed topic.

While reading the svg2 spec about the mesh;
https://svgwg.org/svg2-draft/pservers.html#MeshPatchPainting
I noticed that the definition is different with the definitions of "Gradient Mesh" I read in some papers before:

Paper 1: Image vectorization using optimized gradient meshes
https://dl.acm.org/citation.cfm?id=1276391
https://www.cct.lsu.edu/~fharhad/ganbatte/siggraph2007/CD2/content/papers/011-sun.pdf
// Note: There's typo in the 4x4 matrix C defined in this paper... please refer to the following paper instead.

Paper 2: Automatic and topology-preserving gradient mesh generation for image vectorization
https://dl.acm.org/citation.cfm?id=1531391
http://orca.cf.ac.uk/27764/1/ImageVectorization.pdf

And I believe Adobe Illustrator is also using this "Gradient Mesh" definition, not the current SVG2 definition.

The problem of the current SVG2's mesh definition is that C1 smoothness is not guaranteed on the edge.
For example, at a point (u, 0) (somewhere in the top edge of the mesh), the v-direction differential value is depending on the value of 2 bottom corners & its knots.
OTOH, in the "Gradient Mesh", v-direction differential at (u, 0) is consist of only 2 top corners & knots values. This assures the adjacent patches are C1 continuous as long as they are sharing corners & knots.

Does someone know why SVG2 is using the current definition instead of the Gradient Mesh?

thanks,

Please view or discuss this issue at https://github.com/w3c/svgwg/issues/377 using your GitHub account

Received on Friday, 5 January 2018 16:34:16 UTC