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Re: CubicCurve2D Tracing

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  To: comp.lang.java.gui
mearvk wrote:
> On Mar 8, 12:29 pm, Daniel Pitts
> <newsgroup.spamfil...@virtualinfinity.net> wrote:
>> mearvk wrote:
>>> Given an arbitrary CubicCurve2D how can I iterate along it getting
>>> both the x and y coordinates of the current point as I go?
>>> Thanks.
>> Try: calling getPathIterator on it.
>> <http://java.sun.com/j2se/1.4.2/docs/api/java/awt/Shape.html#getPathIt...)>
>>
>> --
>> Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>
> 
> Looking at the API I think PathIterator's currentSegment() will just
> get me the beginning, end and both control points. What I need is a
> way to, for instance, find the length of or iterate over, pixel by
> pixel, an arbitrary bezier curve. What I am actually doing is trying
> to find the shortest path along a pair of bezier curves (think race
> track) using a third bezier curve (think finding the apex). But how to
> grade the quality of the current best path? Surely the simplest thing
> to do would be to ask how long is the line? I was thinking if there
> were a way to map the start, end, and both control points onto a
> mathematical function, then I could just scale it appropriately and
> iterate pixel by pixel, summing as I go, but I'm not sure if this can
> be done.
This might help:
<http://java.sun.com/j2se/1.4.2/docs/api/java/awt/geom/FlatteningPathIterator.html>

Also, Bezier curves are well defined mathematically, there is quite 
likely a formula to find the length given the endpoints and control points.

A quick google turned up:
<http://www.cit.gu.edu.au/~anthony/info/graphics/bezier.curves>

Its actually an integral, so you are going about it in a reasonable way. 
  FlatteningPathIterator is what you want. Just sum the distance between 
any two endpoints it gives you.
-- 
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>

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CubicCurve2D Tracing "mearvk" <mearvk@THRWHITE.remove-dii-this> - 2011-04-27 15:43 +0000
  Re: CubicCurve2D Tracing "Daniel Pitts" <daniel.pitts@THRWHITE.remove-dii-this> - 2011-04-27 15:43 +0000
    Re: CubicCurve2D Tracing "mearvk" <mearvk@THRWHITE.remove-dii-this> - 2011-04-27 15:43 +0000
      Re: CubicCurve2D Tracing "Daniel Pitts" <daniel.pitts@THRWHITE.remove-dii-this> - 2011-04-27 15:43 +0000
        Re: CubicCurve2D Tracing "mearvk" <mearvk@THRWHITE.remove-dii-this> - 2011-04-27 15:43 +0000
      Re: CubicCurve2D Tracing "tar" <tar@THRWHITE.remove-dii-this> - 2011-04-27 15:43 +0000

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