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27 Oct 2021 07:01:39 EDT (-0400)
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From: Thomas de Groot
Subject: Re: Luna, Moon... desert satellite
Date: 14 Sep 2021 11:24:09
Message: <6140be99$1@news.povray.org>
Op 14-9-2021 om 15:59 schreef Kenneth:
> "Samuel B." <stb### [at] hotmailcom> wrote:
>> "Kenneth" <kdw### [at] gmailcom> wrote:
> 
>>> Superb. With a jet and its contrail superimposed (just for scale) we would be
>>> hard-pressed to discern a difference from a real late-afternoon photo,
>>> made with a telescopic lens.
>>
>> But it's not close enough, since a dedicated individual would eventually observe
>> how the craters don't cast proper shadows near the terminator :/
>>
> 
> I'm still trying to spot those flaws, but I don't see them :-/
> 
> Are these the anomalies that you are seeing? If so, they look to me like the
> kind of craters that happen to have raised edges, thus catching the Sun at such
> a raking angle.
> 
...yes, and half-buried by the Maria material too it seems, thus 
pre-dating or contemporaneous of the Maria formation/development.

-- 
Thomas


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From: Thomas de Groot
Subject: Re: Luna, Moon... desert satellite
Date: 15 Sep 2021 02:24:32
Message: <614191a0@news.povray.org>
Op 14/09/2021 om 10:14 schreef Thomas de Groot:
> Op 14-9-2021 om 01:35 schreef Samuel B.:
>> Thomas de Groot <tho### [at] degrootorg> wrote:
>>> Op 13/09/2021 om 01:14 schreef Samuel B.:
>>>> P.S. If you look closely, you'll find some interesting things... You 
>>>> can see
>>>> what appears to be scratches in the moon's surface.(...) You'll also 
>>>> see what appears to
>>>> be drifts of dust forming sinuous ridges.
>>>
>>> The short answer, for both features: Lunar Rills --> either collapsed or
>>> not, lava tunnels.
>>
>> Thanks for the new term. I think you may be right... mostly.
>>
>> However, I'm not convinced everything we are referring to are the same
>> structures. I looked up an atlas of known moon rilles, and the 
>> features I was
>> initially observing weren't highlighted on the map, nor were what I 
>> saw when I
>> made my first remarks things that resembled rilles in their entirety. 
>> But I'm
>> also not /un/convinced! Some of what I saw may have indeed been 
>> collapsed lava
>> tubes. But some were also on higher portions of low, sloping hills... 
>> the kind
>> of place you would expect a glancing asteroid to leave a mark. And the 
>> sinuous
>> ridges I also observed looked like dust that piled up by heavy winds. 
>> But since
>> I am fully willing to be wrong, I'll accept any and all corrections to my
>> misconceptions ;D
>>
> 
> It /was/ the short answer ;-)
> 
> There probably is happening more than just rills indeed, but I don't 
> know what they could be. There are features that look like lava flows, 
> like in the upper part, against the terminator, and seemingly coming 
> from a (impact) crater. Could you point out those things you see? I am 
> unable to relate them to something I recognise.
> 
> Otherwise, what does NASA say about it all?
> 

Other thought: You are not pointing to the impact ejecta surrounding 
many craters (Tycho is a good example) and extending over significant 
portions of the lunar surface sometimes, are you? In close up, they 
could be the "sinuous ridges" you mentioned.

-- 
Thomas


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From: Jörg "Yadgar" Bleimann
Subject: Re: Luna, Moon... desert satellite
Date: 15 Sep 2021 11:16:43
Message: <61420e5b$1@news.povray.org>
Hi(gh)!

On 11.09.21 23:17, Samuel B. wrote:

> Yes, I think I can help you with. POV-Ray is the program you need. Just use a
> red/green map to build a height_field like you normally would. Situate an
> orthographic camera over the hf, and center the hf to fill the screen. Give the
> hf a planar pigment with a reversed color_map (so that white=peaks) and an
> ambient 1 finish. You may also need to specify the following command line
> options: +fg and File_Gamma=1.0. This is the way I have converted red/green maps
> to 16-bit pngs in the past.

I just saved the TIFF as a PNG... but did not yet find the time to try a 
rendering!

> 
>> Now playing: Love Now Till Eternity (Asia)
> 
> Cool band! I think my favorite is 'Don't Cry'

Mine is "Cutting it Fine"... but overall, it's just poor man's Yes, I 
prefer the genuine stuff!

See you in Khyberspace!

Yadgar

Now playing: Girl with Grey Eyes (Big Country)


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From: Samuel B 
Subject: Re: Luna, Moon... desert satellite
Date: 15 Sep 2021 17:20:00
Message: <web.614262f0756c3d5acb705ca46e741498@news.povray.org>
William F Pokorny <ano### [at] anonymousorg> wrote:
> On 9/12/21 7:14 PM, Samuel B. wrote:
> > "Samuel B." <stb### [at] hotmailcom> wrote:
> >> Just testing out some moon maps.
> >
> > Final render in this series. Zoom in to see all the details.
> >
>
> Hi Sam. Beautiful & interesting.
>
> Though I believe my old eyes are picking up some banding in the posted
> image - away from the moon and where the moon is shadowed. Did you use a
> dithering option while writing the jpg file?

Hi Bill,

Your eyes are keen enough... there is definitely some color banding going on.
And no, I didn't enable dithering :S

Some of the banding on the right side might be exacerbated by the luminous bloom
sampling set I used. I need to make a new sampling set that isn't so regular, or
perhaps I should try to develop a new type of bloom that utilizes averaged noisy
normals. Or maybe I should try the blurred reflections feature in UberPOV...

Sam


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From: Samuel B 
Subject: Re: Luna, Moon... desert satellite
Date: 15 Sep 2021 18:15:00
Message: <web.61426f57756c3d5acb705ca46e741498@news.povray.org>
"Kenneth" <kdw### [at] gmailcom> wrote:
> "Samuel B." <stb### [at] hotmailcom> wrote:
> > But it's not close enough, since a dedicated individual would eventually observe
> > how the craters don't cast proper shadows near the terminator :/
> >
>
> I'm still trying to spot those flaws, but I don't see them :-/

The issue of the craters not casting shadows is just that: if the object was
using actual displaced geometry you would see shadows cast across the basins on
the craters. But all you get on a simple bump-mapped sphere is shading... No
displacement of geometry, no shadows. It's not really a big issue at smaller
resolutions, but I think it is noticeable.

The other features I was talking about are something else. I'll highlight them
in a reply to Thomas.

Sam


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From: Samuel B 
Subject: Re: Luna, Moon... desert satellite
Date: 15 Sep 2021 18:25:00
Message: <web.61427224756c3d5acb705ca46e741498@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:
> Op 14-9-2021 om 01:35 schreef Samuel B.:
> > (...) I'm not convinced everything we are referring to are the same
> > structures. (...)
>
> It /was/ the short answer ;-)
>
> There probably is happening more than just rills indeed, but I don't
> know what they could be. There are features that look like lava flows,
> like in the upper part, against the terminator, and seemingly coming
> from a (impact) crater. Could you point out those things you see? I am
> unable to relate them to something I recognise.

Attached is an image highlighting the areas I was talking about.

"A" points to three features I suspect might have been produced by asteroids
scraping the surface. Notice how they seem to have occurred on the sides or
upper portions of a (really large) sloping hill? To me that indicates they were
perhaps caused by asteroids hitting the moon at glancing angles... But I can
definitely see how they could have been caused by collapsed lava tubes.

"B" encircles the area of sinuous ridges. They do appear to emanate from an
impact site. Are they lava flows as you suggested? Or dust accumulation?

> Otherwise, what does NASA say about it all?

Lol, I should definitely check instead of just guessing. (But guessing is so
much fun sometimes ;))

Sam


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Attachments:
Download 'moonb-areas-of-interest.jpg' (174 KB)

Preview of image 'moonb-areas-of-interest.jpg'
moonb-areas-of-interest.jpg


 

From: Samuel B 
Subject: Re: Luna, Moon... desert satellite
Date: 15 Sep 2021 18:35:00
Message: <web.6142747e756c3d5acb705ca46e741498@news.povray.org>
=?UTF-8?Q?J=c3=b6rg_=22Yadgar=22_Bleimann?= <yaz### [at] gmxde> wrote:
> Hi(gh)!

Hi again Jorg. (For some reason the newsgroups web interface won't render
character alt+0246.)

> On 11.09.21 23:17, Samuel B. wrote:
>
> > Yes, I think I can help you with. POV-Ray is the program you need. Just use a
> > red/green map to build a height_field like you normally would.
>
> I just saved the TIFF as a PNG... but did not yet find the time to try a
> rendering!

Well, if you run into any issues, just holler.

> >> Now playing: Love Now Till Eternity (Asia)
> >
> > Cool band! I think my favorite is 'Don't Cry'
>
> Mine is "Cutting it Fine"... but overall, it's just poor man's Yes, I
> prefer the genuine stuff!

I'll check out that other Asia song. I never really noticed any similarities
between them and Yes... but now you've made me curious. Most of the 80s music is
great, IMO.

Sam


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From: Cousin Ricky
Subject: Re: Luna, Moon... desert satellite
Date: 15 Sep 2021 20:48:49
Message: <61429471$1@news.povray.org>
On 2021-09-15 6:22 PM (-4), Samuel B. wrote:
> 
> "A" points to three features I suspect might have been produced by asteroids
> scraping the surface. Notice how they seem to have occurred on the sides or
> upper portions of a (really large) sloping hill? To me that indicates they were
> perhaps caused by asteroids hitting the moon at glancing angles... But I can
> definitely see how they could have been caused by collapsed lava tubes.

I'm guessing rills; if not that, collapsed lava tubes.  It's not
intuitive, but as far as I know, impact craters are always circular,
regardless of impact angle.  If anything, a glancing impact might create
a series of craters, rather than a linear gouge.


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From: Thomas de Groot
Subject: Re: Luna, Moon... desert satellite
Date: 16 Sep 2021 02:34:42
Message: <6142e582$1@news.povray.org>
Op 16/09/2021 om 00:10 schreef Samuel B.:
> "Kenneth" <kdw### [at] gmailcom> wrote:
>> "Samuel B." <stb### [at] hotmailcom> wrote:
>>> But it's not close enough, since a dedicated individual would eventually observe
>>> how the craters don't cast proper shadows near the terminator :/
>>>
>>
>> I'm still trying to spot those flaws, but I don't see them :-/
> 
> The issue of the craters not casting shadows is just that: if the object was
> using actual displaced geometry you would see shadows cast across the basins on
> the craters. But all you get on a simple bump-mapped sphere is shading... No
> displacement of geometry, no shadows. It's not really a big issue at smaller
> resolutions, but I think it is noticeable.
> 
Ah, yes... that is indeed true. It may account also for the phenomenon I 
observe here, of the lunar light/shadow features optically switching to 
their opposites. I have to zoom out to get the correct aspect again.

> The other features I was talking about are something else. I'll highlight them
> in a reply to Thomas.
> 
See there for some answers.

-- 
Thomas


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From: Alain Martel
Subject: Re: Luna, Moon... desert satellite
Date: 16 Sep 2021 12:02:30
Message: <61436a96$1@news.povray.org>

> On 2021-09-15 6:22 PM (-4), Samuel B. wrote:
>>
>> "A" points to three features I suspect might have been produced by asteroids
>> scraping the surface. Notice how they seem to have occurred on the sides or
>> upper portions of a (really large) sloping hill? To me that indicates they were
>> perhaps caused by asteroids hitting the moon at glancing angles... But I can
>> definitely see how they could have been caused by collapsed lava tubes.
> 
> I'm guessing rills; if not that, collapsed lava tubes.  It's not
> intuitive, but as far as I know, impact craters are always circular,
> regardless of impact angle.  If anything, a glancing impact might create
> a series of craters, rather than a linear gouge.
> 

There are a very few craters that are not circular. You can count them 
on your fingers. When the impact angle is extremely shallow, the crater 
can get elongated.
I've seen photos of three of those.


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