Hello guys,

Is there any macro that supports hermite curves? Does povray support hermite
curves? And what are they really good for? Isn't cubic splines enough to
create any kind of smooth camera or object animation?

Thanks in advance.

Fidel.

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Fidel viegas wrote:
> 
> Hello guys,
> 
> Is there any macro that supports hermite curves? Does povray support hermite
> curves? And what are they really good for? Isn't cubic splines enough to
> create any kind of smooth camera or object animation?

http://www.geocities.com/emory_stagmer/povherm/

-- 
Ken Tyler

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Fidel viegas <fid### [at] artrecognitioncouk> wrote:
> Is there any macro that supports hermite curves? Does povray support
hermite
> curves? And what are they really good for? Isn't cubic splines enough to
> create any kind of smooth camera or object animation?

The term "cubic" refers to the degree of the equations used to calculate the
spline path.  All the cubic splines (Bezier, Catmull-Rom, Hermite,
Kochanek-Bartels) are just different ways of specifying the inputs for the
spline, and it's not too difficult to perform conversions from one to
another.

My Spline Macro File allows you to define and use cubic splines, with a
choice of input types (including Hermite).  A POV 3.5 compatible version is
available on request, although I intend to review and revise the file to
make best use of POV 3.5's inbuilt spline functions.  You can download the
file and a tutorial from http://www.geocities.com/ccolefax

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> The term "cubic" refers to the degree of the equations used to calculate the
> spline path.  All the cubic splines (Bezier, Catmull-Rom, Hermite,
> Kochanek-Bartels) are just different ways of specifying the inputs for the
> spline, and it's not too difficult to perform conversions from one to
> another.

Thanks for the info. I spent a while reading on that subject and just
implemented a java application that converts from one to another.

> My Spline Macro File allows you to define and use cubic splines, with a
> choice of input types (including Hermite).  A POV 3.5 compatible version is
> available on request, although I intend to review and revise the file to
> make best use of POV 3.5's inbuilt spline functions.  You can download the
> file and a tutorial from http://www.geocities.com/ccolefax

I had that on my include path, but had never used it. Anyway, as I mentioned
above, I just implemented an application that allows me to design the
splines visually with mouse clicks. I then export it to povray (I am too
lazy to be doing trial and error experiments with povray sdl until I get the
correct curve).


Thanks for all the support.

All the best

Fidel.

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On Sun, 22 Sep 2002 19:20:02 -0400, Chris Colefax quoth:

> Fidel viegas <fid### [at] artrecognitioncouk> wrote:
>> Is there any macro that supports hermite curves? Does povray support
> hermite
>> curves? And what are they really good for? Isn't cubic splines enough
>> to create any kind of smooth camera or object animation?
> 
> The term "cubic" refers to the degree of the equations used to calculate
> the spline path.  All the cubic splines (Bezier, Catmull-Rom, Hermite,
> Kochanek-Bartels) are just different ways of specifying the inputs for
> the spline, and it's not too difficult to perform conversions from one
> to another.

There's also a "natural cubic spline" type that can't easily be converted
to/from.  POV-Ray 3.5's "natural_spline" is a natural cubic spline.  The
"cubic_spline" type is a Catmull-Rom spline.

-- 
Mark

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Hi Mark,

Thanks for the info.

> There's also a "natural cubic spline" type that can't easily be converted
> to/from.  

There is always a way around it. I haven't looked into it yet, but I am sure
that is a way of converting it to other types of splines and vice-versa,
even though it is hard.

>POV-Ray 3.5's "natural_spline" is a natural cubic spline.  The
> "cubic_spline" type is a Catmull-Rom spline.

I haven't looked into that.
 At the moment I am only using Hermite, Bezier and B-Splines. I'll look into
the others later. Mostly I use Bezier for almost everything, but I wanted to
learn how they work internally.

Once again, thanks very much.

Fidel.

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Would you be willing to share you program? Sounds like it might be very
useful.
Best,
D
"Fidel viegas" <fid### [at] artrecognitioncouk> wrote in message
news:B9B5F5D1.4F12%fid### [at] artrecognitioncouk...
> Hi Mark,
>
> Thanks for the info.
>
> > There's also a "natural cubic spline" type that can't easily be
converted
> > to/from.
>
> There is always a way around it. I haven't looked into it yet, but I am
sure
> that is a way of converting it to other types of splines and vice-versa,
> even though it is hard.
>
> >POV-Ray 3.5's "natural_spline" is a natural cubic spline.  The
> > "cubic_spline" type is a Catmull-Rom spline.
>
> I haven't looked into that.
>  At the moment I am only using Hermite, Bezier and B-Splines. I'll look
into
> the others later. Mostly I use Bezier for almost everything, but I wanted
to
> learn how they work internally.
>
> Once again, thanks very much.
>
> Fidel.
>

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in article 3d90cc4c$1@news.povray.org, Dennis Miller at dhm### [at] attbicom
wrote on 24/9/02 9:32 pm:

> Would you be willing to share you program? Sounds like it might be very
> useful.

Hi Dennis, I will share the program when I finish it. I built it
intentionally to study splines and to generate povray code for me. That way
I can design the splines visually and export it as a prism or as a lathe. At
the moment, it isn't something special. So, I decided to write a real
application and I plan to extend it further and add bicubic patches as well.
But, I am learning the internals of curves and surfaces so that I can  take
it further.
I was thinking something similar to sPatch. Since I now use Mac mostly, I
can't use sPatch. So, I just write special purpose tools to aid my
understanding of povray internals visually.

As soon as I release it, I will alert the pov community since this
application will be specifically for povray.

Anyway, all the best

Fidel.

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Good luck with your work. Sounds very interesting!
d.

"Fidel viegas" <fid### [at] artrecognitioncouk> wrote in message
news:B9B69EA0.4F72%fid### [at] artrecognitioncouk...
> in article 3d90cc4c$1@news.povray.org, Dennis Miller at dhm### [at] attbicom
> wrote on 24/9/02 9:32 pm:
>
> > Would you be willing to share you program? Sounds like it might be very
> > useful.
>
> Hi Dennis, I will share the program when I finish it. I built it
> intentionally to study splines and to generate povray code for me. That
way
> I can design the splines visually and export it as a prism or as a lathe.
At
> the moment, it isn't something special. So, I decided to write a real
> application and I plan to extend it further and add bicubic patches as
well.
> But, I am learning the internals of curves and surfaces so that I can
take
> it further.
> I was thinking something similar to sPatch. Since I now use Mac mostly, I
> can't use sPatch. So, I just write special purpose tools to aid my
> understanding of povray internals visually.
>
> As soon as I release it, I will alert the pov community since this
> application will be specifically for povray.
>
> Anyway, all the best
>
> Fidel.
>

Post a reply to this message