Chris Huff <Chr### [at] compuservecom> wrote:
: bounded_by does work differently for isosurfaces, it creates a shape
: with a closed surface where it intersects the bounding shape, while
: clipped by works the same but leaves that area open.

  Is it so? Then I really don't like it. If bounded_by works in one way
with one object and in other way with other object, that definitely is not
a good thing. Bounded_by should always work as a bounded_by, not as an
intesection CSG.
  Using bounded_by for other reasons than limiting the object is quite rare,
but not impossible. If it doesn't work equally for all objects, you are
breaking the functionality of the povray engine.
  If I want to clip an object and add new surfaces to the clipped parts, I
use intersection. If I want to clip and object without adding new surfaces
I will use clipped_by. For bounding I will use bounding_by and I will expect
it to work as with all the other objects (for example with quartics, which
also are isosurfaces).
  Sometimes you _want_ the side-effects of bounding objects (for example
for the so-called 'vampire' or 'anti-vampire' objects).

  If I know povteam, I will not be surprised if they changed the behaviour
of bounded_by for isosurfaces to work exactly like for other objects in
pov3.5. I approve this idea. I don't like the idea of bounded_by working
in different ways for different objects.

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

Post a reply to this message

David Heys <cel### [at] hotmailcom> schreef in berichtnieuws
37C1E489.68910B68@hotmail.com...
> ........
> I "did" get an interesting effect with this:
> ......
> 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?

David,

Try adding (a higher value for) the max_intersections statement in the
isosurface object. Due to a bug the maximum for this is 10.


ingo

Post a reply to this message

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

Post a reply to this message

I tend to agree, there should be a separate keyword(limit_object?
limited_by?) and the inconsistency is annoying. I don't think it would
be difficult at all to do this, but I don't know anything about the
isosurface source.(This "bounding" shape is necessary for the
calculation method to work)
However, I think you can still declare an isosurface, and then manually
bound an instance of that isosurface, and it will work normally. I
haven't tried it, though, but if it works, it would allow vampire
isosurfaces, etc.

Post a reply to this message

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? 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

Post a reply to this message

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

Post a reply to this message

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

Post a reply to this message

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.

Post a reply to this message

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