smellenbergh wrote:

> SamuelT. <STB### [at] aolcom> wrote:
>
> > Oh, could I get some feedback about the tutorial? Either a post or e-mail
> > is fine. I just need to know if it is worth putting up more isosurface
> > tutorials. Thanks.
> >
> Hi,
> It sure is worth it.
> Actually: "does anyone know about docs or a tutorial for the
> isosurface?"" has become a FAQ in these newsgroups.
>
> We often see stunning isosurface images. Only to make us wish we knew
> more about maths. Your tutorial shows that it isn't that difficult after
> all.
> Please go on with it.
>
> -smellenbergh
>
> --
> e-mail:sme### [at] skynetbe
>
> Site of the POV-RayUnofficial for Macintosh (isosurface patch included)
> http://users.skynet.be/smellenbergh

Thank you for the support! I'm glad you were able to understand it :)

--
Samuel Benge

STB### [at] aolcom

"While you were sleeping
he went on keeping the final line in his mind."
 -Tortoise and the Hare, The Moody Blues

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David Heys wrote:

> Hey Samuel,
>
> I notice there are a lot of predetermined functions already. Thing like
> Torus (which you mentioned) and Mesh (I just saw on:
>
> http://www.etl.go.jp/etl/linac/public/rsuzuki/e/povray/iso/index.html
> Which is one of the sites that detail (to some degree) the isosurface
> patch. This is the same one that's built into Superpatch, right?

By having that link, you know about as much as I do about the predefined
functions.

It is pretty much the same patch; you can call up sphere and torus in the
new Superpatch.



> How can
> I:
>
> a) Find a list of all these predefined functions and a description of
> what shapes they produce.
>
> b) See the actual math of these functions if I want to play with one or
> more of them?
>
> David

I wish I knew. Perhaps you can e-mail the owner of that site?

I really only know what I saw on that site and what I've experimented with
when it comes to isosurfaces.

--
Samuel Benge

STB### [at] aolcom

"While you were sleeping
he went on keeping the final line in his mind."
 -Tortoise and the Hare, The Moody Blues

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On Mon, 23 Aug 1999 16:17:14 -0800, David Heys wrote:

>I have a question on this as well. I'll post an image in
>binaries.images. I tried plunking a light inside this object. Light
>pours out quite nicely onto the plane that intersects the object, but
>does not shine within (even with a Hollow added to the isosurface and
>torus). It's almost as if the "holes" in the object let light pass
>through, but not impact upon the interior of the object. Am I wrong in
>this?

You probably need to increase max_trace (not max_trace_level, but the
max_trace parameter in the isosurface declaration).  The docs say you 
should use max_trace all_intersections, but that's broken in the current 
version.  I'd use the lowest number that works.

Post a reply to this message

On 24 Aug 1999 04:17:16 -0400, Nieminen Juha wrote:
>  I started to read this tutorial and found the first error in less than
>one minute... :)
>  I quote:
>
>> bounded_by - This gives the isosurface a limit. For instance, if you make an
>> isosurface sphere that is larger than 1 at its radius, and you put 
>
>> bounded_by{ box{ <-1,-1,-1>,<1,1,1> } } 
>
>> in the isosurface statement, what do you think will happen? The box will
>> cut into the sphere, giving you an intersected box and sphere, the sphere
>> having 6 flat sides. 
>
>  I don't know if this works differently with isosurfaces since I have never
>used the superpatch, but if bounded_by works as usual, that's not true.

bounded_by doesn't work as usual.  In fact, some builtin functions, such as 
rounded_box, actually use the bounds to determine their size.  Not the best
design, I'll admit.

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On Tue, 24 Aug 1999 17:15:20 -0800, David Heys wrote:

>I notice there are a lot of predetermined functions already. Thing like
>Torus (which you mentioned) and Mesh (I just saw on:
>
>http://www.etl.go.jp/etl/linac/public/rsuzuki/e/povray/iso/index.html
>
>Which is one of the sites that detail (to some degree) the isosurface
>patch. This is the same one that's built into Superpatch, right? How can
>I:
>
>a) Find a list of all these predefined functions and a description of
>what shapes they produce.
>
>b) See the actual math of these functions if I want to play with one or
>more of them?

For both answers, get a copy of the source code and look at isofunc.c .
Not all of the builtins are just straight functions; some of them, such
as rounded box, are complex conditional expressions.

If you just want the builtins and their parameters, look at the superpatch
docs or at this page from R. Suzuki's old POV 2.2 equipotsurface patch, 
where I got the docs from originally:

http://www.etl.go.jp/etl/linac/public/rsuzuki/e/povray/exmplint.htm

Post a reply to this message

Ron Parker wrote:

> http://www.etl.go.jp/etl/linac/public/rsuzuki/e/povray/exmplint.htm

 Ron,

  You by any chance have any more links to sites that contain Pov patches ?
I have been filling in that section of my links page and would like to
add any you may have that I am missing.

Thanks in advance,

-- 
Ken Tyler

See my 850+ Povray and 3D Rendering and Raytracing Links at:
http://home.pacbell.net/tylereng/index.html

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On Wed, 25 Aug 1999 07:28:43 -0700, Ken wrote:
>
>
>Ron Parker wrote:
>
>> http://www.etl.go.jp/etl/linac/public/rsuzuki/e/povray/exmplint.htm
>
> Ron,
>
>  You by any chance have any more links to sites that contain Pov patches ?
>I have been filling in that section of my links page and would like to
>add any you may have that I am missing.

I do, somewhere.  Obviously I have links to the patches that are included
in the superpatch, where such links exist, but you seem to already have
most of those.  I also have links to some other patches that I haven't 
included yet, such as povafx and some others.  I'll see what I can find 
this evening and send it to you.

Post a reply to this message

Ron Parker wrote:

> I do, somewhere.  Obviously I have links to the patches that are included
> in the superpatch, where such links exist, but you seem to already have
> most of those.  I also have links to some other patches that I haven't
> included yet, such as povafx and some others.  I'll see what I can find
> this evening and send it to you.

Thanks and no rush on this. Any time this week would be fine.

-- 
Ken Tyler

See my 850+ Povray and 3D Rendering and Raytracing Links at:
http://home.pacbell.net/tylereng/index.html

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SamuelT. <STB### [at] aolcom> wrote :
>
> What do you need to know?
>

    Well, I am trying to figure out what the base assumption of isosurface
is...

ie: "Show every point which is inside (outside?) the area defined by the
function"
    or...
     "Show those x points which are above y and z but under threshold"

    or whatever.. I haven't figured it out yet and every time I get a
working theory I make an image which contraverts that theory.

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It is "show all points where the function is equal to the threshold."
Bounding and clipping shapes will alter it if the surface is not totally
contained in the bounding shape.

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