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"Dave Blandston" <nomail@nomail> wrote:
> Glad you found a solution!
cheers Dave. too late, it seems, to be of use to COMPATT.
regards, jr.
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"jr" <cre### [at] gmail com> wrote:
> with 'polarity on'
??
What's that? I must have missed a new feature(?) somehow...
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hi,
"Kenneth" <kdw### [at] gmailcom> wrote:
> "jr" <cre### [at] gmailcom> wrote:
> > with 'polarity on'
> ??
> What's that? I must have missed a new feature(?) somehow...
looks like you did. :-) the last paragraph in section "3.5.1.1.6 Isosurface"
in the 3.8 docs reads:
By default, the inside of an isosurface is defined as the set of all points
inside the contained_by shape where the function values are below the threshold.
New in version 3.8 this can be changed via the polarity keyword. Specifying a
positive setting or on will instead cause function values above the threshold to
be considered inside. Specifying a negative setting or off will give the default
behavior.
regards, jr.
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"jr" <cre### [at] gmailcom> wrote:
> hi,
>
> "Kenneth" <kdw### [at] gmailcom> wrote:
> > "jr" <cre### [at] gmailcom> wrote:
> > > with 'polarity on'
> > ??
> > What's that? I must have missed a new feature(?) somehow...
>
> looks like you did. :-) the last paragraph in section "3.5.1.1.6 Isosurface"
> in the 3.8 docs reads: ...
>
Thanks! Yep, it's new to me. (And I was wondering where those moire patterns
were coming from-- thinking that the planet was just a simple sphere object, not
an isosurface.)
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"Kenneth" <kdw### [at] gmailcom> wrote:
>
> ...And I was wondering where those moire patterns
> were coming from-- thinking that the planet was just a simple sphere object, not
> an isosurface.)
Just took a look at COMPATT's previous post about this. Duh.
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From: Thomas de Groot
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 7 Jan 2019 02:40:03
Message: <5c330253$1@news.povray.org>
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On 6-1-2019 19:43, jr wrote:
> hi,
>
> "Kenneth" <kdw### [at] gmailcom> wrote:
>> "jr" <cre### [at] gmailcom> wrote:
>>> with 'polarity on'
>> ??
>> What's that? I must have missed a new feature(?) somehow...
>
> looks like you did. :-) the last paragraph in section "3.5.1.1.6 Isosurface"
> in the 3.8 docs reads:
>
> By default, the inside of an isosurface is defined as the set of all points
> inside the contained_by shape where the function values are below the threshold.
> New in version 3.8 this can be changed via the polarity keyword. Specifying a
> positive setting or on will instead cause function values above the threshold to
> be considered inside. Specifying a negative setting or off will give the default
> behavior.
>
Interesting. I missed that too. Going to play right now as I am working
on an isosurface...
--
Thomas
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From: Thomas de Groot
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 7 Jan 2019 02:50:01
Message: <5c3304a9$1@news.povray.org>
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On 7-1-2019 8:40, Thomas de Groot wrote:
>
> Interesting. I missed that too. Going to play right now as I am working
> on an isosurface...
>
Hmmm... right. Not what I expected. Polarity may be only relevant if the
contained_by shape is close to the isosurface one, i.e. spheres,
cylinders, cubes. Otherwise, I don't understand its usefulness. Polarity
on just renders the contained_by shape, whatever its (positive) value.
Did I miss something? Probably.
--
Thomas
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From: clipka
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 7 Jan 2019 05:45:39
Message: <5c332dd3$1@news.povray.org>
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Am 07.01.2019 um 08:49 schrieb Thomas de Groot:
> On 7-1-2019 8:40, Thomas de Groot wrote:
>>
>> Interesting. I missed that too. Going to play right now as I am
>> working on an isosurface...
>>
>
> Hmmm... right. Not what I expected. Polarity may be only relevant if the
> contained_by shape is close to the isosurface one, i.e. spheres,
> cylinders, cubes. Otherwise, I don't understand its usefulness. Polarity
> on just renders the contained_by shape, whatever its (positive) value.
>
> Did I miss something? Probably.
The magnitude of the `polarity` paramezer is irrelevant, only the sign
matters (or, more precisely, whether the parameter is positive; zero has
the same effect as a negative value).
`polarity 1` should have the same effect as flipping the signs of both
the function and the threshold.
If your isosurface is fully inside the `contained_by` shpe, then it is
perfectly normal that `polarity 1` will cause you to see only the
`contained_by` shape, because everything outside the `contained_by`
shape is always considered "outside" (*), while inside that shape the
"inside" and "outside" are now the other way round.
To just flip "inside" and "outside" (including the space outside the
`contained_by` shape, you should use the `inverse` keyword instead.
The `polarity` keyword is primarily intended to complement the
`potential` pattern feature, which would behave inconsistently between
blobs and isosurfaces unless positive polarity mode is used for the latter.
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From: Thomas de Groot
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 7 Jan 2019 06:54:11
Message: <5c333de3$1@news.povray.org>
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On 7-1-2019 11:45, clipka wrote:
> Am 07.01.2019 um 08:49 schrieb Thomas de Groot:
>> On 7-1-2019 8:40, Thomas de Groot wrote:
>>>
>>> Interesting. I missed that too. Going to play right now as I am
>>> working on an isosurface...
>>>
>>
>> Hmmm... right. Not what I expected. Polarity may be only relevant if
>> the contained_by shape is close to the isosurface one, i.e. spheres,
>> cylinders, cubes. Otherwise, I don't understand its usefulness.
>> Polarity on just renders the contained_by shape, whatever its
>> (positive) value.
>>
>> Did I miss something? Probably.
>
> The magnitude of the `polarity` paramezer is irrelevant, only the sign
> matters (or, more precisely, whether the parameter is positive; zero has
> the same effect as a negative value).
>
> `polarity 1` should have the same effect as flipping the signs of both
> the function and the threshold.
>
> If your isosurface is fully inside the `contained_by` shpe, then it is
> perfectly normal that `polarity 1` will cause you to see only the
> `contained_by` shape, because everything outside the `contained_by`
> shape is always considered "outside" (*), while inside that shape the
> "inside" and "outside" are now the other way round.
>
> To just flip "inside" and "outside" (including the space outside the
> `contained_by` shape, you should use the `inverse` keyword instead.
>
>
> The `polarity` keyword is primarily intended to complement the
> `potential` pattern feature, which would behave inconsistently between
> blobs and isosurfaces unless positive polarity mode is used for the latter.
OK, I guess I understand. I then wonder if the polarity use by Jr to
solve COMPATT's problem is correct. My uneducated guess would be 'no'. ;-)
--
Thomas
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hi,
clipka <ano### [at] anonymousorg> wrote:
> Am 07.01.2019 um 08:49 schrieb Thomas de Groot:
> > On 7-1-2019 8:40, Thomas de Groot wrote:
> > Hmmm... right. Not what I expected. ...
>
> The magnitude of the `polarity` paramezer is irrelevant, only the sign
> matters (or, more precisely, whether the parameter is positive; zero has
> the same effect as a negative value).
so why is the parameter a float, when (just) a boolean would seem to be a better
fit? future expansion?
regards, jr.
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