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16 Jun 2021 10:02:29 EDT (-0400)
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From: Thomas de Groot
Subject: Re: Granites Intermezzo
Date: 27 Apr 2021 03:03:14
Message: <6087b732$1@news.povray.org>
Op 26/04/2021 om 12:47 schreef Bald Eagle:

>
http://news.povray.org/povray.general/thread/%3C5ae17c9c%40news.povray.org%3E/?mtop=422221&moff=10
> 
>
http://news.povray.org/povray.binaries.images/thread/%3Cweb.5ad633941828641ca47873e10%40news.povray.org%3E/?mtop=422589
> 

Thanks for the reminder. I found test scene files I made back then from 
these posts.

So much we forget... The Search option of the POV-Ray site works 
adequately, but often I need something more sophisticated...

-- 
Thomas


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From: Mr
Subject: Re: Granites Intermezzo
Date: 27 Apr 2021 06:35:00
Message: <web.6087e81ecfb077e46adeaecb3f378f2@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:
> This is a version of the frosted granite, with quartz veins, but also
> with ligh-coloured minerals in the matrix.
>
> --
> Thomas

To my profane eye this scale variation looks very natural! (though it remains to
be seen if it still holds from close up and when the pattern will be the real
one)


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From: Bald Eagle
Subject: Re: Granites Intermezzo
Date: 27 Apr 2021 06:40:00
Message: <web.6087e9d4cfb077e41f9dae3025979125@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:

> The original granite code contains turbulence. That is one of the
> reasons the original granite looks like a 'flow' pattern. The first
> thing I did was to comment out the turbulence; the granite became more
> 'crispy' and closer to the real thing.

Ah.  The pattern is also gradient noise based, which causes smooth blending
between the values, and creates a "roundness" - the rolling hills of a
heightfield.  I looked into modifying that, and I got something that's at least
good enough for some experiments to see if it's worth any more pursuit.


> That is a tedious exercise ;-) I did it years ago to get correct colour
> values for Mediterranean-style roof tiles (for which I used the cells
> pattern, btw). Can be done of course; I shall put it on my
> ToDo/ToExplore list.

Maybe eval_pigment and that histogram macro in .... math.inc?

> All the above: yes; might need additional investigation. Concerning the
> hexagon pattern: many if not most of the granite minerals are hexagonal.
> That would mean it would be more appropriate for granites. However, I am
> afraid it would look 'circular' in practice.

Yes, a slice down the side of a hexagonal basalt column would give a
rectangle...
Maybe layered patterns with all but the base having a mostly clear pigment in
the map.  That way we could just "sprinkle" a few different shapes in and not
have to do a lot of math / algorithms / pattern tweaking, and still get the
crisp grain boundaries.


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Attachments:
Download 'stepnoise.png' (229 KB)

Preview of image 'stepnoise.png'
stepnoise.png


 

From: Bald Eagle
Subject: Re: Granites Intermezzo
Date: 27 Apr 2021 06:50:00
Message: <web.6087ec44cfb077e41f9dae3025979125@news.povray.org>
"Mr" <nomail@nomail> wrote:

> To my profane eye this scale variation looks very natural! (though it remains to
> be seen if it still holds from close up and when the pattern will be the real
> one)

Yes, this reminds me to
a) comment on that:  It looks very VERY good.   The improvements really make a
huge difference.  I think that it's really a LOT better than the original.
Excellent work, Thomas.

and B)
Blender has a granite shader pack that maybe we can get some hints from  ;)
https://blendermarket.com/products/procedural-granite-shader-pack/


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From: Thomas de Groot
Subject: Re: Granites Intermezzo
Date: 27 Apr 2021 07:32:34
Message: <6087f652$1@news.povray.org>
Op 27-4-2021 om 12:49 schreef Bald Eagle:
> "Mr" <nomail@nomail> wrote:
> 
>> To my profane eye this scale variation looks very natural! (though it remains to
>> be seen if it still holds from close up and when the pattern will be the real
>> one)
> 
> Yes, this reminds me to
> a) comment on that:  It looks very VERY good.   The improvements really make a
> huge difference.  I think that it's really a LOT better than the original.
> Excellent work, Thomas.
> 
Thank you, sir.

I am /beginning/ to feel some satisfaction myself ;-) It is better to 
test on the frosted version than on the polished one. No surprise there.

Not yet there however...

> and B)
> Blender has a granite shader pack that maybe we can get some hints from  ;)
> https://blendermarket.com/products/procedural-granite-shader-pack/
> 
Thou shalt not bow to foreign idols! :-)

I shall have a peep... From the images shown, especially the Dakota 
Mahogany, it appears to me (gut feeling) that a 'granite' pattern was 
used; the minerals' shape appear somewhat like my initial texture.

-- 
Thomas


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From: Bald Eagle
Subject: Re: Granites Intermezzo
Date: 27 Apr 2021 18:20:00
Message: <web.60888d70cfb077e41f9dae3025979125@news.povray.org>
Here's the half-noise half-cells pattern I worked out.

Adjusting Start and End to be both 0.5 gives results identical to cells.   Due
to the smoothstep, you can never get pure gradient noise.

I thought it was wasted time as it still has some gradient to it, but with
double-entry color_maps, you get a sharp delineation anyway...

Please "give it the treatment" and see if this produces something better or
worse than the turbulated cells.

(And your email bounced me.  :P)


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Attachments:
Download 'stepnoise.pov.txt' (3 KB)

From: Thomas de Groot
Subject: Re: Granites Intermezzo
Date: 28 Apr 2021 02:26:06
Message: <6088fffe$1@news.povray.org>
Op 28/04/2021 om 00:17 schreef Bald Eagle:
> Here's the half-noise half-cells pattern I worked out.
> 
> Adjusting Start and End to be both 0.5 gives results identical to cells.   Due
> to the smoothstep, you can never get pure gradient noise.
> 
> I thought it was wasted time as it still has some gradient to it, but with
> double-entry color_maps, you get a sharp delineation anyway...
> 
> Please "give it the treatment" and see if this produces something better or
> worse than the turbulated cells.
> 
Thanks. Preparing the scalpels now...

> (And your email bounced me.  :P)
> 
Hu?

-- 
Thomas


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From: Bald Eagle
Subject: Re: Granites Intermezzo
Date: 28 Apr 2021 06:50:00
Message: <web.60893d6ccfb077e41f9dae3025979125@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:

> > (And your email bounced me.  :P)
> >
> Hu?

Undelivered Mail Returned to Sender

Mail Delivery System (MAI### [at] mailvanrycknet)

This is the mail system at host mail.vanryck.net.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                  The mail system

<_ple### [at] localhostlocaldomain>: Think about your  life
    decisions. Think about them!

.... etc.


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From: Thomas de Groot
Subject: Re: Granites Intermezzo
Date: 28 Apr 2021 07:56:20
Message: <60894d64$1@news.povray.org>
Op 28-4-2021 om 12:48 schreef Bald Eagle:
> Thomas de Groot <tho### [at] degrootorg> wrote:
> 
>>> (And your email bounced me.  :P)
>>>
>> Hu?
> 
> Undelivered Mail Returned to Sender
> 
> Mail Delivery System (MAI### [at] mailvanrycknet)
> 
> This is the mail system at host mail.vanryck.net.
> 
> I'm sorry to have to inform you that your message could not
> be delivered to one or more recipients. It's attached below.
> 
> For further assistance, please send mail to postmaster.
> 
> If you do so, please include this problem report. You can
> delete your own text from the attached returned message.
> 
>                    The mail system
> 
> <_ple### [at] localhostlocaldomain>: Think about your  life
>      decisions. Think about them!
> 
> .... etc.
> 

Aha! Yes! The phony mail address. Fooled you :-)

-- 
Thomas


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From: Thomas de Groot
Subject: Re: Granites Intermezzo
Date: 28 Apr 2021 11:02:30
Message: <60897906$1@news.povray.org>
Op 28-4-2021 om 00:17 schreef Bald Eagle:
> Here's the half-noise half-cells pattern I worked out.
> 
> Adjusting Start and End to be both 0.5 gives results identical to cells.   Due
> to the smoothstep, you can never get pure gradient noise.
> 
> I thought it was wasted time as it still has some gradient to it, but with
> double-entry color_maps, you get a sharp delineation anyway...
> 
> Please "give it the treatment" and see if this produces something better or
> worse than the turbulated cells.
> 

Busy still. Started late today. Already can say that StepNoise might be 
*IT*. It looks great. Shall be back tomorrow with more comments.

-- 
Thomas


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