POV-Ray : Newsgroups : povray.general : Splines Server Time
27 Jul 2024 16:30:55 EDT (-0400)
  Splines (Message 5 to 14 of 14)  
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From: yesbird
Subject: Re: Splines
Date: 12 Jul 2024 12:46:48
Message: <66915df8$1@news.povray.org>
On 12/07/2024 11:53, kurtz le pirate wrote:
> There are a few things I didn't understand.
> Is there a doc, a web page, ... that explains POV splines
> in more detail ?

There was a discussion about strange POV splines behaviour, somehow I've
forced it to work, but the control and implementation are still mystery
to me:
news://news.povray.org:119/64105423$1@news.povray.org
-- 
YB


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From: William F Pokorny
Subject: Re: Splines
Date: 12 Jul 2024 15:09:55
Message: <66917f83$1@news.povray.org>
On 7/12/24 12:46, yesbird wrote:
> On 12/07/2024 11:53, kurtz le pirate wrote:
>> There are a few things I didn't understand.
>> Is there a doc, a web page, ... that explains POV splines
>> in more detail ?
> 
> There was a discussion about strange POV splines behaviour, somehow I've
> forced it to work, but the control and implementation are still mystery
> to me:
> news://news.povray.org:119/64105423$1@news.povray.org

Another form of the link which might be easier to use:

https://news.povray.org/povray.advanced-users/thread/%3C85b87be3-7ea0-95d9-62fa-0aa3cad0a315%40gmail.com%3E/

Bill P.


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From: yesbird
Subject: Re: Splines
Date: 12 Jul 2024 16:46:14
Message: <66919616$1@news.povray.org>
On 12/07/2024 22:09, William F Pokorny wrote:
> Another form of the link which might be easier to use: ...

Thanks, I will take it into account, but how you got it ?
I was using: RightClick -> "Copy Message Location" in Thunderbird.
--
YB


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From: Bald Eagle
Subject: Re: Splines
Date: 12 Jul 2024 16:55:00
Message: <web.669197ccaeceb7471f9dae3025979125@news.povray.org>
yesbird <sya### [at] gmailcom> wrote:
> On 12/07/2024 22:09, William F Pokorny wrote:
> > Another form of the link which might be easier to use: ...
>
> Thanks, I will take it into account, but how you got it ?
> I was using: RightClick -> "Copy Message Location" in Thunderbird.
> --
> YB

Use the URL in the browser/web interface
http://news.povray.org/


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From: Josh English
Subject: Re: Splines
Date: 12 Jul 2024 23:20:14
Message: <6691f26e$1@news.povray.org>
On 7/12/2024 1:53 AM, kurtz le pirate wrote:
> 
> Hello,
> 
> I'm now looking at splines and trying to understand how POVRay treats
> this object.
> 

Your understanding is correct. Here's an example with:
a) simpler coordinates
b) an array for tracking the indices.

It ain't pretty, but it works.

The points 0, 3, 6, and 9 are points on the curve.

Point 0 has control points 11 and 1
Point 3 has control points 2 and 4
Point 6 has control points 5 and 7
Point 9 has control points 8 and 10

Josh


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Attachments:
Download 'spline_question_answer.pov.txt' (2 KB) Download 'spline_question_answer.png' (8 KB)

Preview of image 'spline_question_answer.png'
spline_question_answer.png


 

From: yesbird
Subject: Re: Splines
Date: 13 Jul 2024 02:59:52
Message: <669225e8$1@news.povray.org>
On 12/07/2024 23:53, Bald Eagle wrote:
> Use the URL in the browser/web interface
> http://news.povray.org/

Thanks.
--
YB.


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From: kurtz le pirate
Subject: Re: Splines
Date: 13 Jul 2024 09:10:06
Message: <66927cae@news.povray.org>
In fact, it's simple !


Each segment is defined by four points.

First segment :
0 : Point on curve
1 : Control point attached to point (0)
2 : Control point attached to the next point
3 : Next point

Second segment :
4 : Point on curve equal to (3) from previous segment
5 : Control point attached to point (4)
6 : Control point attached to the next point
7 : Next point

... and so on.


In the attached image, the points are numbered and named in accordance
with POV's built-in spline editor : "S. Cs. Ce. E.".
I haven't found what these names correspond to.


The complete curve is therefore the succession of segments placed
end to end.

In the image, each element of each segment has the same color :
Segment 1 - Point 0,1,2,3 - Color Green
Segment 2 - Point 4,5,6,7 - Color Magenta
Segment 3 - Point 8,9,10,11 - Color Blue


Disturbingly, the two pendulums of the same point are identified by two
distinct segments. Once you've got the hang of it, it's no longer a problem.




-- 
Kurtz le pirate
Compagnie de la Banquise


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Attachments:
Download 'drawing_bezier_spline_editor.png' (38 KB)

Preview of image 'drawing_bezier_spline_editor.png'
drawing_bezier_spline_editor.png


 

From: Bald Eagle
Subject: Re: Splines
Date: 13 Jul 2024 15:15:00
Message: <web.6692d15caeceb7471f9dae3025979125@news.povray.org>
kurtz le pirate <kur### [at] gmailcom> wrote:

> In the attached image, the points are numbered and named in accordance
> with POV's built-in spline editor : "S. Cs. Ce. E.".
> I haven't found what these names correspond to.

> POV's built-in spline editor (?)

"S. Cs. Ce. E.".
I haven't found what these names correspond to.

Start
Control (point) Start
Control (point) End
End

?

Or something like that.


I'm glad you got it all worked out.
Hopefully you have an interesting project to apply it to.

- BW


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From: Cousin Ricky
Subject: Re: Splines
Date: 15 Jul 2024 13:04:44
Message: <669556ac$1@news.povray.org>
On 2024-07-13 09:10 (-4), kurtz le pirate wrote:
> 
> In the attached image, the points are numbered and named in accordance
> with POV's built-in spline editor : "S. Cs. Ce. E.".

POV has a built-in spline editor?  When did this happen?  Is it a
Windows thing?


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From: kurtz le pirate
Subject: Re: Splines
Date: 16 Jul 2024 09:16:41
Message: <669672b9@news.povray.org>
On 15/07/2024 19:04, Cousin Ricky wrote:

> POV has a built-in spline editor?  When did this happen?  Is it a
> Windows thing?

No, it's a Mac OSX feature.



-- 
Kurtz le pirate
Compagnie de la Banquise


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Attachments:
Download 'spline_editor.jpg' (293 KB)

Preview of image 'spline_editor.jpg'
spline_editor.jpg


 

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