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On 5/21/07, MenTaLguY <mental@...3...> wrote:
<mesh xml:id="foo" meshUnits="userSpaceOnUse"> <vertex vertex-color="#27D" vertex-opacity="0.5" x="12.7" y="3.5"/> <vertex vertex-color="rgb(123, 254, 37)" vertex-opacity="1" x="8.4" y="17.2"/> <vertex vertex-color="#F0D" vertex-opacity="0" x="3.2" y="14.1"/> </mesh>
Certainly this approach is a lot more practical for the implementor compared to the one where you explicitly specify all the edges and faces. Automatic triangulation should be relatively easy.
However, I'm concerned that this approach may not be too useful for the designer. Yes, it is very easy to drag around the vertices and the mesh will respond intuituvely. But the result won't look like _anything_ in the real world. It will be too linear, too clunky, with too visible vertices and edges. That's inevitable if you go with straight line edges and linear color transitions between nodes, as your plan implies.
The only way to use this to render something real-life-like is by using a LOT of vertices so that the triangles are too small to be visible. But IMHO that makes the whole affair rather meaningless. It is unthinkable to create such tight meshes manually, so Inkscape developers will have to provide yet another UI level on top of this - using, most likely, bezier-based meshed like in Adobe Illustrator - and then approximate the results using such a triangulated mesh. This will blow up the size of SVG files considerably, and the mapping from the triangulated approximation to the higher-level curvilinear representation and back will be far from trivial to implement. Actually, the proposed triangulated mesh in SVG won't buy us much at all, because we can just as well approximate a bezier-based AI-like mesh with small triangles or (better) beziergon paths right now (see http://inkscape.org/screenshots/gallery/inkscape-0.45-gradient-mesh-experime...), and it won't be _much_ worse or less efficient than if we used the triangulated mesh.
Xara X has, along with elliptic and linear gradients, the "three-color" gradient fill which looks exactly like one cell from a triangulation that you propose. Since it's just a single cell it's not an entirely fair comparison, but I can say that in several years of my using Xara for a lot of different design projects, I have never once found use for such gradients. A few times I thought I might use them, but when I actually tried, they always turned out too awkard, too sharp near the corners, too linear. So in the end I usually made do with something like several overlapping elliptic gradients instead. To my knowledge, other Xara artists are not often using this gradient type either - so much so that I could not even google up any example image to show you. On the other hand, it is well known that the lack of bezier-controlled gradient meshes like those in AI is one of the most frequent complaints of Xara users and is what drives some of them to defect from Xara to AI. For me, it is obvious that three-point gradients will never truly fulfill that need even if I can do a whole triangulated mesh of such gradients. Smooth *curvilinear* controls are absolutely crucial if you're doing any photorealistic art (and photorealistic art is what gradient meshed in AI are most often used for).