Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.java.gui > #3240 > unrolled thread

CubicCurve2D Tracing

Back to article view | Back to comp.lang.java.gui

Contents

  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

#3240 — CubicCurve2D Tracing

  To: comp.lang.java.gui
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.

---
 * Synchronet * The Whitehouse BBS --- whitehouse.hulds.com --- check it out free usenet!
--- Synchronet 3.15a-Win32 NewsLink 1.92
Time Warp of the Future BBS - telnet://time.synchro.net:24

[toc] | [next] | [standalone]

#3248

  To: comp.lang.java.gui
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#getPathIterator(java.awt.geom.AffineTransform)>


-- 
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>

---
 * Synchronet * The Whitehouse BBS --- whitehouse.hulds.com --- check it out free usenet!
--- Synchronet 3.15a-Win32 NewsLink 1.92
Time Warp of the Future BBS - telnet://time.synchro.net:24

[toc] | [prev] | [next] | [standalone]

#3249

  To: comp.lang.java.gui
On Mar 8, 12:29=A0pm, 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.

---
 * Synchronet * The Whitehouse BBS --- whitehouse.hulds.com --- check it out free usenet!
--- Synchronet 3.15a-Win32 NewsLink 1.92
Time Warp of the Future BBS - telnet://time.synchro.net:24

[toc] | [prev] | [next] | [standalone]

#3254

  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/>

---
 * Synchronet * The Whitehouse BBS --- whitehouse.hulds.com --- check it out free usenet!
--- Synchronet 3.15a-Win32 NewsLink 1.92
Time Warp of the Future BBS - telnet://time.synchro.net:24

[toc] | [prev] | [next] | [standalone]

#3262

  To: comp.lang.java.gui
On Mar 10, 11:01=A0am, Daniel Pitts
<newsgroup.spamfil...@virtualinfinity.net> wrote:
> 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/FlatteningPathI...>=

>
> 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.
> =A0 FlatteningPathIterator is what you want. Just sum the distance between=

> any two endpoints it gives you.
> --
> Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>- Hide quo=
ted text -
>
> - Show quoted text -

Thank you both.

---
 * Synchronet * The Whitehouse BBS --- whitehouse.hulds.com --- check it out free usenet!
--- Synchronet 3.15a-Win32 NewsLink 1.92
Time Warp of the Future BBS - telnet://time.synchro.net:24

[toc] | [prev] | [next] | [standalone]

#3255

  To: comp.lang.java.gui

Well, you can get some results by Googling "bezier curve length"

One promising approach, with C code, is:

  <http://steve.hollasch.net/cgindex/curves/cbezarclen.html>



-- 
Thomas A. Russ,  USC/Information Sciences Institute

---
 * Synchronet * The Whitehouse BBS --- whitehouse.hulds.com --- check it out free usenet!
--- Synchronet 3.15a-Win32 NewsLink 1.92
Time Warp of the Future BBS - telnet://time.synchro.net:24

[toc] | [prev] | [standalone]

Back to top | Article view | comp.lang.java.gui

csiph-web