Chris Huff wrote:
> 
> In article <3872a859@news.povray.org>, "Patrick Dugan"
> <pat### [at] netinsnet> wrote:
> 
> > But WHY is there a torus depression?  The torus should carve out ONLY
> > where
> > the intersection of the height field and torus intersect, not have an
> > "extra" area showing outside of the heightfield.  While a "clear" pigment
> > works it is still not behaving the way a standard solid object would.
> 
> I am not sure what you mean. It behaves in exactly the same way a
> standard object does. A difference operation leaves the surface of the
> differencing object on the object being differenced.

For what it is worth I agree with Chris's assessment of the operation.
Practice differencing a small sphere from the face of a box or a plane
and you will see what he means.

-- 
Ken Tyler -  1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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Patrick Dugan <pat### [at] netinsnet> wrote in message
news:3872a859@news.povray.org...
> But WHY is there a torus depression?  The torus should carve out ONLY
where
> the intersection of the height field and torus intersect, not have an
> "extra" area showing outside of the heightfield.  While a "clear" pigment
> works it is still not behaving the way a standard solid object would.

Maybe you have the heightfield upside down and are looking at the underside
of your heightfield?
Just an idea...

Johannes.

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Chris Huff wrote:

> Don't get confused by the fact that you can see under the top surface of
> the height field, the object is there, there just aren't any surfaces
> around that portion of it. The lower boundaries are set by a cube, 

If I remember well, the "lower" part of the "inside" of a HF extends
to the infinity, just like a plane does.

Fabien.

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In article <38738237.B782BECC@skynet.be>, Fabien Mosen 
<fab### [at] skynetbe> wrote:

> If I remember well, the "lower" part of the "inside" of a HF extends
> to the infinity, just like a plane does.

Hmm, it seems you are right. I was fooled by the section of the 
documentation that says the height field fills a 1*1*1 box. I assumed 
all points in that box and under the height field were considered 
"inside".

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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On Wed, 05 Jan 2000 18:41:11 +0100, Fabien Mosen
<fab### [at] skynetbe> wrote:

>Chris Huff wrote:
>
>> Don't get confused by the fact that you can see under the top surface of
>> the height field, the object is there, there just aren't any surfaces
>> around that portion of it. The lower boundaries are set by a cube, 
>
>If I remember well, the "lower" part of the "inside" of a HF extends
>to the infinity, just like a plane does.
>
>Fabien.

I think you're right but it is also automaticallt bounded by a unit
box and this may cause problems if you try to access the volume below
the x-z plane.


Peter Popov
pet### [at] usanet
ICQ: 15002700

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