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I use a cubic spline, and I want a curve something like this:
(ASCII art, use monospace font)
o
_-
__-
o-------o-------o--
But instead I get something like this:
o
_-
__--
o-------o----___o-
The curve goes a bit down before it goes up, and I don't want that.
I know *why* this happens, but I don't know how to avoid it.
Using a different spline type is not an option.
Maybe a can insert an extra control point or two, but where is it most
effective to put it?
Any "tricks"?
Rune
--
\ Include files, tutorials, 3D images, raytracing jokes,
/ The POV Desktop Theme, and The POV-Ray Logo Contest can
\ all be found at http://rsj.mobilixnet.dk (updated October 9)
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Rune <run### [at] iname com> wrote:
: o
: _-
: __--
: o-------o----___o-
: The curve goes a bit down before it goes up, and I don't want that.
: I know *why* this happens, but I don't know how to avoid it.
Raise the third point a bit.
It's just a property of the spline. It's not working "wrong" or anything,
it just works like that.
As said, raising the third point a bit should help.
Now, it's an interesting question, how much should it be raise to get a
perfect solution.
(Btw, you'll probably need to raise the second point a bit as well if
you don't want the curve to go down anywhere.)
--
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/
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Rune wrote:
>
>
> o
> _-
> __--
> o-------o----___o- <=======
>
I'm not very experienced with splines, but putting one or several extra
points where the arrow points could help.
Christoph
--
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other
things on: http://www.schunter.etc.tu-bs.de/~chris/
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Christoph Hormann <chr### [at] gmxde> schrieb in im
Newsbeitrag: 3A2A7D6A.D2C02B28@gmx.de...
>
>
> Rune wrote:
> >
> >
> > o
> > _-
> > __--
> > o-------o----___o- <=======
> >
>
> I'm not very experienced with splines, but putting one or
several extra
> points where the arrow points could help.
>
I think this would make it even more difficult ...
it would go with the same amount down, but it would be thinner in
the horizontal direction...
For me it is a rule, that the closer the controlpoints of a
spline are, the harder it is to control...
it would help a bit, to raise the third point (as Warp already
said) and maybe the second a bit ...
If it is a cubic spline, than you would need AFAIK three
controlpoints to come from a round part of the spline to a
straight line ...
If you want it faster, that you should try to use beziers ...
--
,', Jan Walzer \V/ http://wa.lzer.net ,',
',',' student of >|< mailto:jan### [at] lzernet ',','
' ComputerScience /A\ +49-177-7403863 '
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"Warp" wrote:
> It's just a property of the spline. It's not working "wrong"
> or anything, it just works like that.
Yes, I know.
> As said, raising the third point a bit should help.
Thanks, I'll try it out.
Rune
--
\ Include files, tutorials, 3D images, raytracing jokes,
/ The POV Desktop Theme, and The POV-Ray Logo Contest can
\ all be found at http://rsj.mobilixnet.dk (updated October 9)
/ Also visit http://www.povrayusers.org
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Rune wrote:
>
> I use a cubic spline, and I want a curve something like this:
> (ASCII art, use monospace font)
>
> o
> _-
> __-
> o-------o-------o--
>
> But instead I get something like this:
>
> o
> _-
> __--
> o-------o----___o-
>
> The curve goes a bit down before it goes up, and I don't want that.
> I know *why* this happens, but I don't know how to avoid it.
> Using a different spline type is not an option.
>
> Maybe a can insert an extra control point or two, but where is it most
> effective to put it?
> Any "tricks"?
That is the way it is supposed to work. It has to go down to smooth 2,
3 and 4. You should see the line between 1 and 2 going up a little.
Move your third point from the left control point further along the
curve.
--
Any law passed for political reasons is the creation
of a political crime.
-- The Iron Webmaster, 21
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Rune, I find that using one of the nifty spline editors listed on the
POV links page is a good way to generate splines and export the points
to pov for further tweaking....
I like this one:
http://www.flashnet.it/users/fn027571/spil/main.html
-paul
Rune wrote:
>
> I use a cubic spline, and I want a curve something like this:
> (ASCII art, use monospace font)
>
> o
> _-
> __-
> o-------o-------o--
>
> But instead I get something like this:
>
> o
> _-
> __--
> o-------o----___o-
>
> The curve goes a bit down before it goes up, and I don't want that.
> I know *why* this happens, but I don't know how to avoid it.
> Using a different spline type is not an option.
>
> Maybe a can insert an extra control point or two, but where is it most
> effective to put it?
> Any "tricks"?
>
> Rune
> --
> \ Include files, tutorials, 3D images, raytracing jokes,
> / The POV Desktop Theme, and The POV-Ray Logo Contest can
> \ all be found at http://rsj.mobilixnet.dk (updated October 9)
> / Also visit http://www.povrayusers.org
--
--------------------------------------------------}
Paul Daniel Jones
The Pennslyvania State University
pdj### [at] psuedu
http://research.chem.psu.edu/glassgrp/paul
C The way is near, but men
// \ seek it afar. It is in the
N N easy things, but men seek it
| || in the difficult things.
C C -Menicius
\\ /
C
--------------------------------------------------}
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"Matt Giwer" wrote:
> That is the way it is supposed to work.
Yes, I know :)
> Move your third point from the left control point further
> along the curve.
Thanks, I'll try it out.
Rune
--
\ Include files, tutorials, 3D images, raytracing jokes,
/ The POV Desktop Theme, and The POV-Ray Logo Contest can
\ all be found at http://rsj.mobilixnet.dk (updated October 9)
/ Also visit http://www.povrayusers.org
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"Paul Jones" wrote:
> Rune, I find that using one of the nifty spline editors
> listed on the POV links page is a good way to generate
> splines and export the points to pov for further tweaking....
>
> I like this one:
>
> http://www.flashnet.it/users/fn027571/spil/main.html
Thanks for the link, it looks like a very handy program, though not for this
particular problem.
My spline is a 3D spline plus time as the 4th dimension, so the program
won't be able to handle it.
Rune
--
\ Include files, tutorials, 3D images, raytracing jokes,
/ The POV Desktop Theme, and The POV-Ray Logo Contest can
\ all be found at http://rsj.mobilixnet.dk (updated October 9)
/ Also visit http://www.povrayusers.org
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