Re: [Lib2geom-devel] [Inkscape-devel] Curve fitting (was Including BSD-Licenced code in Inkscape)

[Nathan H. <nj...@nj...>]

If we can just constrain the code licence to match the 2geom one, I
think everything is fine, otherwise I guess we could include separate
licencing for just this piece of code.

I'm happy to do a code review if you remind me in a few weeks.

njh

On Thu, Dec 01, 2016 at 07:52:06AM +0100, Tavmjong Bah wrote:
> 
> Hi Alexander,
> 
> Looks interesting.
> 
> As you are proposing this as an addition to lib2geom, the proper place
> to discuss this is on the lib2geom-devel list (lib2geom is a semi-
> independent project):
> 
>     lib...@li...
> 
> Tav
> 
>  
> > Hi,
> > 
> > I added a curve fitting algorithm to 2geom which takes a std::vector
> > of
> > Geom::Point and fits a Geom::CubicBezier to the points.
> > 
> > It fits (non-degenerate) cubic bezier curves to given points within
> > half
> > a millisecond up to an error of 1e-9.
> > 
> > You can find it here:
> > https://github.com/abrock/lib2geom
> > 
> > In src/test/bezier-fit-test.cpp I made three simple tests,
> > one "normal" curve and two (nearly) degenerate curves with (nearly)
> > colinear points.
> > I create a Cubic Bezier, select 20 points and give these to the
> > fitting
> > function (which doesn't know the original curve).
> > 
> > Results:
> > 
> > Normal Curve:
> > Speed: 2678 curves per second
> > Worst error: 1.31799e-10 at t=0.736842
> > 
> > Degenerate Curve:
> > New method: 1567.89 curves per second
> > Worst error: 6.84045e-09 at t=0.110945
> > 
> > Nearly degenerate curve:
> > New method: 534.738 curves per second
> > Worst error: 0.0284499 at t=0.0958247
> > 
> > in src/2geom/bezier-utils.cpp are the new functions:
> > 
> > - fit_bezier sets up the nonlinear least squares problem
> > 
> > Helper functions:
> > - bezierfit_f calculates residuals
> > - bezierfit_df calculates derivatives of residuals
> > - bezier_distance helps calculating derivatives, it mainly contains a
> > templated evaluation of Cubic Bezier functions.
> > 
> > src/2geom/jet.h contains the implementation of dual numbers I copied
> > from the Ceres source code
> > 
> > Best Regards,
> > Alexander
> > 
> > -------------------------------------------------------------------
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