Nice. How are you testing for flatness?
Adaptive subdivision of quad curves reduces the required number of vertices by 30-50% (versus using a fixed number of subdivisions (=10), at my selected error tolerance)
(and check out that sweet visualization of post-vertex geometry, courtesy of Xcode 10 
)pic.twitter.com/7ofok0wLD5
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I test whether the distance from the midpoint of the curve segment subtended by a candidate secant line and the midpoint of the corresponding chord are within a tolerance. Simplified from the antigrain approach described here: http://antigrain.com/research/adaptive_bezier#toc0004 …
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It’s rudimentary, but it works all right in practice.pic.twitter.com/7Omxz8POA2
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Does this work with quad and cubic beziers?
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This isn’t backed by rigorous analysis, but I think the edge-case failures would be worse with cubics. I haven’t tried, and the code doesn’t attempt to handle cubics.
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Ah gotcha. I've been putting off implementing a scan converter/rasterizer for CGPaths looking for better algorithms - Loop/Blinn is the simpler/newer one that comes to mind?
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Loop-Blinn is straightforward enough if you can pre-tessellate your paths. I think Slug is the current state of the art, though proprietary. Pathfinder takes a different tack and is open-source (Rust).
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Yeah... I think due to the complexity I'll have to stick with a simple scan converter (which is the CA impl anyway so I've got a resource to look at).
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So how do you get the font rendering itself correct? From my understanding, you need to take care of things like kerning, ligatures, and a host of stuff which would font rendering really complex.
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That’s why I punt to Core Text for all of that
It gives me the laid-out glyph positions and paths, and I tesselate them to produce the mesh.
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Great. I’d be really interested in taking a look.
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CPU or GPU?
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All pre-tesselated on CPU with libtess2.
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Interesting. :3c
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