Can anyone tell me how the built in isosurface function helix1
works. I tried

isosurface {
 function { "helix1" <2,1,0.2,1,0,1,0> }
 threshold 1
 sign 1
 pigment {Red}
}

but just got a cylinder.

Any help will be appreciated.

Thanks
Gail
*******************************************************************
* gsh### [at] monotixcoza              * ERROR: COFFEE.COM not found  *
* http://www.rucus.ru.ac.za/~gail/ * Insert cup and press any key *
*******************************************************************
   My Software never has bugs, It just develops random features
*******************************************************************

Post a reply to this message

On Thu, 2 Sep 1999 17:06:21 +0200, Gail Shaw wrote:
>Can anyone tell me how the built in isosurface function helix1
>works. I tried
>
>isosurface {
> function { "helix1" <2,1,0.2,1,0,1,0> }
> threshold 1
> sign 1
> pigment {Red}
>}
>
>but just got a cylinder.
>
>Any help will be appreciated.

Try this:


isosurface {
 function { "helix1" <2,1,0.2,1,1,1,0> }
 threshold 0
 max_gradient 20 method 2
 bounded_by {box {-10,10}}
 sign 1         
 pigment {red 1} finish {ambient .4}
}

Most of the internal functions are designed to work with a threshold of
zero.  By default, they're bounded by a small box, so you need to add a
bounding volume if you want to see anything interesting.  I also added
the max_gradient 20 method 2 to eliminate some gaps in the result.

Finally, the docs for parameter 4 ("shape parameter") are useless, but
a little playing shows that it is the ratio of height to width for the
ellipses the "strands" are made out of.  Zero is a bad number, and will
in fact crash on some architectures.  Replacing it with a one gives 
you a circular cross-section, which is what I assume you wanted.  I'll
try to remember to fix this in the next version of the docs.

Post a reply to this message

Ron Parker wrote in message <37ce9813@news.povray.org>...
>On Thu, 2 Sep 1999 17:06:21 +0200, Gail Shaw wrote:
>Try this:
>
>
>isosurface {
> function { "helix1" <2,1,0.2,1,1,1,0> }
> threshold 0
> max_gradient 20 method 2
> bounded_by {box {-10,10}}
> sign 1
> pigment {red 1} finish {ambient .4}
>}
>
>Most of the internal functions are designed to work with a threshold of
>zero.  By default, they're bounded by a small box, so you need to add a
>bounding volume if you want to see anything interesting.  I also added
>the max_gradient 20 method 2 to eliminate some gaps in the result.
>
>Finally, the docs for parameter 4 ("shape parameter") are useless, but
>a little playing shows that it is the ratio of height to width for the
>ellipses the "strands" are made out of.  Zero is a bad number, and will
>in fact crash on some architectures.  Replacing it with a one gives
>you a circular cross-section, which is what I assume you wanted.  I'll
>try to remember to fix this in the next version of the docs.


Thanks, that's basically what I wanted.

Next question. Can I use the isosurface functions within media.

I seem to vaguely remember a discussion on that, can't remember when or
where
though

Thanks
Gail
*******************************************************************
* gsh### [at] monotixcoza              * ERROR: COFFEE.COM not found  *
* http://www.rucus.ru.ac.za/~gail/ * Insert cup and press any key *
*******************************************************************
   My Software never has bugs, It just develops random features
*******************************************************************

Post a reply to this message

Yes, they can be used in media, or in place of any other pattern. Just
use function {function stuff here} in place of the pattern name.

Post a reply to this message