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28 Mar 2024 08:43:16 EDT (-0400)
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From: jr
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 7 Jan 2019 07:20:01
Message: <web.5c3343a446f01a8148892b50@news.povray.org>
hi,

Thomas de Groot <tho### [at] degrootorg> wrote:
> 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'. ;-)

correct, hence "I'm sure it isn't "the correct way" of doing, but.." result.

btw, is your computer's clock off by (about) 2 minutes?


regards, jr.


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From: jr
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 7 Jan 2019 07:50:00
Message: <web.5c334a6946f01a8148892b50@news.povray.org>
hi,

"Kenneth" <kdw### [at] gmailcom> wrote:
> "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.

the clue was in the title!  :-)  (more of a grin ;-))


regards, jr.


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From: clipka
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 7 Jan 2019 11:22:10
Message: <5c337cb2$1@news.povray.org>
Am 07.01.2019 um 12:53 schrieb jr:

>> 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?

No; I just think the parameter should be `polarity SIGN` rather than 
`positive_polarity BOOL`; but POV-Ray doesn't have a `SIGN` type, so I 
went for the next best thing, which is the sign of a `FLOAT`. So in a 
sense the "most official" syntax is `polarity +1` or `polarity -1`.

Since this has the side effect that `polarity on` /will/ also inevitably 
work, I opted to make `polarity off` work as well (meaning `polarity 0` 
would have to act like `polarity -1`).

Allowing for arbitrary magnitude was also pretty much a no-brainer, 
because it simplifies the implementation, while having the side effect 
that it is easier to use in cases where the polarity might be derived 
from some computed value.


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From: jr
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 7 Jan 2019 12:20:03
Message: <web.5c33898c46f01a8148892b50@news.povray.org>
hi,

clipka <ano### [at] anonymousorg> wrote:
> Am 07.01.2019 um 12:53 schrieb jr:
> > so why is the parameter a float, when (just) a boolean would seem to be a better
> > fit?  future expansion?
>
> No; I just think the parameter should be `polarity SIGN` rather than
> `positive_polarity BOOL`; but POV-Ray doesn't have a `SIGN` type, so I
> went for the next best thing, which is the sign of a `FLOAT`. So in a
> sense the "most official" syntax is `polarity +1` or `polarity -1`.
>
> Since this has the side effect that `polarity on` /will/ also inevitably
> work, I opted to make `polarity off` work as well (meaning `polarity 0`
> would have to act like `polarity -1`).

ah, thank you.


> Allowing for arbitrary magnitude was also pretty much a no-brainer,
> because it simplifies the implementation, while having the side effect
> that it is easier to use in cases where the polarity might be derived
> from some computed value.



regards, jr.


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From: Kenneth
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 7 Jan 2019 15:10:01
Message: <web.5c33b14046f01a81cd98345b0@news.povray.org>
"jr" <cre### [at] gmailcom> wrote:
> >
> > Just took a look at COMPATT's previous post about this. Duh.
>
> the clue was in the title!  :-)  (more of a grin ;-))
>
>
The title! Hmm, it must have been written in invisible ink...  :-O


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From: Thomas de Groot
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 8 Jan 2019 02:32:14
Message: <5c3451fe$1@news.povray.org>
On 7-1-2019 13:18, jr wrote:
> hi,
> 
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> 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'. ;-)
> 
> correct, hence "I'm sure it isn't "the correct way" of doing, but.." result.
> 
> btw, is your computer's clock off by (about) 2 minutes?
> 

LOL

No, not that I am aware of. My clock is synchronised (time.windows.com).

-- 
Thomas


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From: jr
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 8 Jan 2019 04:35:01
Message: <web.5c346e7f46f01a8148892b50@news.povray.org>
hi,

Thomas de Groot <tho### [at] degrootorg> wrote:
> On 7-1-2019 13:18, jr wrote:
> > btw, is your computer's clock off by (about) 2 minutes?
> No, not that I am aware of. My clock is synchronised (time.windows.com).

strange, I see a '7 Jan 2019 12:20:01' timestamp for the message you replied to,
while you saw '7-1-2019 13:18'.  why 58 minutes?

(I use uk.pool.ntp.org to provide time)

regards, jr.


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From: Thomas de Groot
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 8 Jan 2019 06:52:21
Message: <5c348ef5$1@news.povray.org>
On 8-1-2019 10:33, jr wrote:
> hi,
> 
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> On 7-1-2019 13:18, jr wrote:
>>> btw, is your computer's clock off by (about) 2 minutes?
>> No, not that I am aware of. My clock is synchronised (time.windows.com).
> 
> strange, I see a '7 Jan 2019 12:20:01' timestamp for the message you replied to,
> while you saw '7-1-2019 13:18'.  why 58 minutes?
> 
> (I use uk.pool.ntp.org to provide time)
> 
> regards, jr.
>


I have no idea. The arcane workings of the internet are way beyond my 
understanding. ;-)

thought: I read and write to the povray ngs using Thunderbird. Maybe 
there is a time delay between writing and effective appearance on the 
website?

-- 
Thomas


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From: clipka
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 8 Jan 2019 08:34:57
Message: <5c34a701$1@news.povray.org>
Am 08.01.2019 um 10:33 schrieb jr:
> hi,
> 
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> On 7-1-2019 13:18, jr wrote:
>>> btw, is your computer's clock off by (about) 2 minutes?
>> No, not that I am aware of. My clock is synchronised (time.windows.com).
> 
> strange, I see a '7 Jan 2019 12:20:01' timestamp for the message you replied to,
> while you saw '7-1-2019 13:18'.  why 58 minutes?

Such a difference would not be caused by a desynchronized clock on the 
reading computer, because the timestamp is an immutable value in the 
message, created when the message is written. The displaying computer 
may apply an offset based on the timezone it has configured, but that's 
always multiples of 30 minutes, and is independent of the current time 
on the computer. (E.g. you could set your computer's clock off by 7 days 
11 hours and 12 minutes, and the message's timestamp would still only be 
offset by less than 24 hours.)

Thomas' theory that it may be caused by the web frontend has some 
merits: It may be that the web frontend creates its own timestamp when 
it processes the message, and that may well be about 2 minutes after the 
message is originally posted via the NNTP protocol. So the web version 
of the replied-to post may have a different timestamp than the NNTP version.


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From: jr
Subject: Re: Moire patterns when trying to create isosurface sphere
Date: 8 Jan 2019 16:00:01
Message: <web.5c350efe46f01a8148892b50@news.povray.org>
hi,

Thomas de Groot <tho### [at] degrootorg> wrote:
> thought: I read and write to the povray ngs using Thunderbird. Maybe
> there is a time delay between writing and effective appearance on the
> website?

that would seem to be the difference (cf clipka's post), I use the web
interface.


regards, jr.


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