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Looking for curve generating functionality

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  Looking for curve generating functionality Jeff Higgins <jeff@example.com> - 2023-04-12 00:53 +0000
    Re: Looking for curve generating functionality Jeff Higgins <jeff@example.com> - 2023-04-12 04:06 +0000
      Re: Looking for curve generating functionality Arne Vajhøj <arne@vajhoej.dk> - 2023-04-16 20:00 -0400

#39942 — Looking for curve generating functionality

Hi all.
I am investigating the problem of solving jigsaw puzzles.
So, to start, I need to generate jigsaw puzzles. I found the
article "Generating SVG Jigsaw Puzzles" and am currently using
the given code to generate puzzles and their pieces. The given
code is written in javascript. The article located at
https://dev.inventables.com/2016/02/26/generating-svg-jigsaw-puzzles.html
and is well written, ad-free, and contains all source code.

My first instinct was to translate the code to Java, but was
stopped almost immediately for the lack of a curve generating
function that is supplied in the javascript library D3.js used
in the article, but not in java.awt.geom. The author describes
this curve as a "B-spline, with control point duplication on the ends".
The article contains a nice interactive demo of the curve.

So my workflow at present is generate the puzzle pieces using
the given javascript, output SVG, use the Java Batik library
to convert the SVG to java.awt.geom.Path2d objects. Messy.

The paths produced by this contain five CubicCurve2d segments
and determining the needed parameters is considerably more complex.
I haven't been able to easily and reliably duplicate the
functionality in Java.

My math skills are not up to the task of understanding splines
so searching the web produces mostly content that I am  not able
to consume. Adding Java to the search terms hasn't been much help.

I am hoping that someone will take the interest to glance at the
article and be able to some suggest some available Java functionality
to replace the D3.js functionality.

Thanks much in advance.
Jeff Higgins

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#39943

On Wed, 12 Apr 2023 00:53:24 -0000 (UTC), Jeff Higgins wrote:

> Hi all.

Actually  the code that generates the curve is not shown in the article.

  var d3CurvedLine = d3_shape.line().curve(d3_shape.curveBasis);

  var piecePathData = function(piece) {
    return piece.map(function(edge) {
      return d3CurvedLine(edge);
    }).join(" ");
  };

When I look at the D3 documentation: 
https://github.com/d3/d3-shape#curves

I see that d3.curveBasis
"Produces a cubic basis spline using the specified control points.
The first and last points are triplicated such that the spline starts
at the first point and ends at the last point, and is tangent to the
line between the first and second points, and to the line between
the penultimate and last points."

And using the nugget of info here:
https://stackoverflow.com/a/26707244/17085543

I believe that what I have is a cubic basis spline of degree 2
with six knots and four control points. Which is Greek to me.

But - allowed me to find TinySpline:
https://github.com/msteinbeck/tinyspline
Which promises Java bindings.
And may provide what I'm looking for ... I'll see.

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#39944

On 4/12/2023 12:06 AM, Jeff Higgins wrote:
> On Wed, 12 Apr 2023 00:53:24 -0000 (UTC), Jeff Higgins wrote:
> Actually  the code that generates the curve is not shown in the article.
> 
>    var d3CurvedLine = d3_shape.line().curve(d3_shape.curveBasis);
> 
>    var piecePathData = function(piece) {
>      return piece.map(function(edge) {
>        return d3CurvedLine(edge);
>      }).join(" ");
>    };
> 
> When I look at the D3 documentation:
> https://github.com/d3/d3-shape#curves
> 
> I see that d3.curveBasis
> "Produces a cubic basis spline using the specified control points.
> The first and last points are triplicated such that the spline starts
> at the first point and ends at the last point, and is tangent to the
> line between the first and second points, and to the line between
> the penultimate and last points."
> 
> And using the nugget of info here:
> https://stackoverflow.com/a/26707244/17085543
> 
> I believe that what I have is a cubic basis spline of degree 2
> with six knots and four control points. Which is Greek to me.
> 
> But - allowed me to find TinySpline:
> https://github.com/msteinbeck/tinyspline
> Which promises Java bindings.
> And may provide what I'm looking for ... I'll see.

Google also found:

https://commons.apache.org/proper/commons-math/javadocs/api-3.6.1/org/apache/commons/math3/analysis/interpolation/SplineInterpolator.html

Arne

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