For your judgment.

A comparison of different versions of Dakota Red (aka Mahogany) granites:

-The first row are the original textures, rendered with Ive's code;
-the second row are my "original"(*) textures with 'rgb' replaced simply 
by 'srgb';
- the third row are my "original"(*) textures with 'rgb' converted to 
'srgb';

At the right, a few Real World Dakota Red photographs from the net.

(*) I noticed that the colour_maps from the original code by Daniel 
Mecklenburg Jr in 1996 are of the form < 0.09, 0.03, 0.06 >, while my 
own originals are of the form < 0.086, 0.027, 0.059 >. So it seems that 
in between 1996 and an unknown (earlier? later?) date, another version 
was posted in the POV-Ray universe...

-- 
Thomas

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Attachments:
Download 'granites.jpg' (839 KB)

Preview of image 'granites.jpg'

Thomas de Groot <tho### [at] degrootorg> wrote:
> For your judgment.

Well, it looks like the simple procedural noise that's used for the basis
pattern is much too round and smooth.  The grains in the real granite are much
sharper and [rect]angular.

It's not clear to me exactly how to achieve that,
but I think that there should be a move away from a very smooth gradient noise,
toward something that will give a more crystalline, granular look, perhaps with
an asymmetric step to it - to make those quartz outlines in the one sample.

Could you please try:

#declare Granite = pigment {
     cells turbulence 0.425 //(0.325 is too low)
     color_map {Whatever you're using}
}

to see what I mean?
I'm interested in seeing a similar render to what you just posted, perhaps with
whatever improvements you might discover.



https://wiki.povray.org/content/HowTo:Turn_a_continuous_function_into_a_stepped_function
https://stackoverflow.com/questions/42823308/make-perlin-noise-with-sharp-edges

Post a reply to this message

Op 25/04/2021 om 21:49 schreef Bald Eagle:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> For your judgment.
> 
> Well, it looks like the simple procedural noise that's used for the basis
> pattern is much too round and smooth.  The grains in the real granite are much
> sharper and [rect]angular.
> 
Yes, that is one of my worries.

> It's not clear to me exactly how to achieve that,
> but I think that there should be a move away from a very smooth gradient noise,
> toward something that will give a more crystalline, granular look, perhaps with
> an asymmetric step to it - to make those quartz outlines in the one sample.
> 
The granite pattern is (almost) correct (without the turbulence).

> Could you please try:
> 
> #declare Granite = pigment {
>       cells turbulence 0.425 //(0.325 is too low)
>       color_map {Whatever you're using}
> }
> 
> to see what I mean?
> I'm interested in seeing a similar render to what you just posted, perhaps with
> whatever improvements you might discover.
> 
Sure.

>
https://wiki.povray.org/content/HowTo:Turn_a_continuous_function_into_a_stepped_function
> https://stackoverflow.com/questions/42823308/make-perlin-noise-with-sharp-edges
> 

HOWEVER!
I should have made my first intention with this image more clear as the 
grain form and distribution are the next steps.

It is the /texture colour/ which prompted my post: It appears - and not 
only with this particular texture - that the original ones, rendered 
with Ive's code (deprecated gamma 1.8, etc) are similar to my own 
version of the set when using /srgb/ instead of /rgb/ in the 
colour_maps! This is interesting because it means that only a minimum of 
conversion is needed to get identical results to the originals. The case 
of the frosted granite is different as the first author used a different 
colour_map for that one in the first place. I do not know why. To be 
investigated.

It also explains more comprehensively the original name: Mahogany. The 
colour is similar to mahogany wood. Afaiac, I believe I should follow 
that path in the first place and maybe disregard my own lighter version 
(or not). Not sure yet. What do you think? Independently of your 
comments above which are of a different order of course.

-- 
Thomas

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Op 25/04/2021 om 21:49 schreef Bald Eagle:
> Could you please try:
> 
> #declare Granite = pigment {
>       cells turbulence 0.425 //(0.325 is too low)
>       color_map {Whatever you're using}
> }
> 
> to see what I mean?
> I'm interested in seeing a similar render to what you just posted, perhaps with
> whatever improvements you might discover.
> 

Quick-and-Dirty.

Yes, this is promising indeed! Good thinking!

-- 
Thomas

Post a reply to this message

Attachments:
Download 'dakotagrains_test.jpg' (88 KB)

Preview of image 'dakotagrains_test.jpg'

Op 26/04/2021 om 08:55 schreef Thomas de Groot:
> Quick-and-Dirty.
> 
> Yes, this is promising indeed! Good thinking!
> 

...and with an appropriate pigment_pattern.

Later today I shall study those two sites and see if I can use the info.

-- 
Thomas

Post a reply to this message

Attachments:
Download 'dakotagrains_test.jpg' (100 KB)

Preview of image 'dakotagrains_test.jpg'

Thomas de Groot <tho### [at] degrootorg> wrote:

Thanks for making the render.  Looks better than my sphere - which looks like a
cheap hard-rubber bowling ball, or the foam they use in sofa cushions.  :D

Needs 0.2-0.3 more turbulence. ;)

> The granite pattern is (almost) correct (without the turbulence).

I don't know what you mean.

> It also explains more comprehensively the original name: Mahogany. The
> colour is similar to mahogany wood. Afaiac, I believe I should follow
> that path in the first place and maybe disregard my own lighter version
> (or not). Not sure yet. What do you think?

Well, there are myriad samples available at stonecontact-dot-com, all of which
fall under the blanket/umbrella trade name of Dakota Mahogany and which have
widely differing "color maps".

I think we need to alternate in our approach to this, and on the one hand try to
formulaicly mimic the underlying patterns and sub-patterns, but on the other
hand not forget that we can do some good ole' raytracing sleight-of-hand and do
everything we can to fool the eye and mind into believing that they see
something that is not there.

One thing I thought of was to take a/some granite photos and run some
edge-finding filters on them to see what pops out.

I'm curious about the rgb color mapping - the individual values - but also,
given an individual grain region, what is the rgb variation across it?  How much
secondary or tertiary pigment is patterned into the grain?

Is there a way to estimate the grain sizes from the photos?  Or maybe there is
statistical data in the literature?

I ran across a neat conformal mapping image with circle packing that looked like
a good mathematical way to get discrete regions with good grain-size variation.

AFAIK, we're using straight Perlin noise right now for granite.   Doing floor()
on each of the axes produces the cells {} pattern.  I'm thinking if we could
split the difference.... maybe with the step trick and/or select ()

Also need to keep in mind that the base pattern might just be a guide, and the
final "look" is going to likely be a result of layering textures/materials.
Hard to visualize.

And lastly, there were the brick pattern and random hexagon color threads that
employed methods we might be able to use here.

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

Post a reply to this message

Thomas de Groot <tho### [at] degrootorg> wrote:
> Op 26/04/2021 om 08:55 schreef Thomas de Groot:
> > Quick-and-Dirty.
> >
> > Yes, this is promising indeed! Good thinking!
> >
>
> ...and with an appropriate pigment_pattern.
>
> Later today I shall study those two sites and see if I can use the info.
>
> --
> Thomas

Exciting ! Now the tint looks spot on and better than the original.
About pattern, however, the fact that both Ive's and your own "quick and dirty"
versions feel more pleasing seems to confirm that the flakes scale may be
slightly too small, even for realistic measurements. Though I do understand that
Ive's scale is not acceptable to the rock specialist's expertise. Maybe a
compromise could be found if the noise depth is not yet too low and could be
reduced one level so as not to generate too small of a minimal cell?

Post a reply to this message

Op 26-4-2021 om 13:11 schreef Mr:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> Op 26/04/2021 om 08:55 schreef Thomas de Groot:
>>> Quick-and-Dirty.
>>>
>>> Yes, this is promising indeed! Good thinking!
>>>
>>
>> ...and with an appropriate pigment_pattern.
>>
>> Later today I shall study those two sites and see if I can use the info.
>>
>> --
>> Thomas
> 
> Exciting ! Now the tint looks spot on and better than the original.
> About pattern, however, the fact that both Ive's and your own "quick and dirty"
> versions feel more pleasing seems to confirm that the flakes scale may be
> slightly too small, even for realistic measurements. Though I do understand that
> Ive's scale is not acceptable to the rock specialist's expertise. Maybe a
> compromise could be found if the noise depth is not yet too low and could be
> reduced one level so as not to generate too small of a minimal cell?
> 
Finding the correct size/distribution of individual minerals is going to 
be a careful and slow process. Each pattern has its own range of scales; 
if I concentrate on /cells/ as in the latest image, the smallest should 
be a bit larger and the largest a bit smaller. ;-)

However, even in a RW granite, the very smallest minerals can only be 
distinguished through a microscope, forming  the basic matrix of the 
rock. Largest minerals can be really large, forming so-called 
/phenocrysts/. For those interested: 
https://en.wikipedia.org/wiki/Phenocryst .

-- 
Thomas

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This is a version of the frosted granite, with quartz veins, but also 
with ligh-coloured minerals in the matrix.

-- 
Thomas

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Attachments:
Download 'dakotagrains_test.jpg' (104 KB)

Preview of image 'dakotagrains_test.jpg'

Op 26/04/2021 om 12:47 schreef Bald Eagle:
> Thomas de Groot <tho### [at] degrootorg> wrote:
> 
> Thanks for making the render.  Looks better than my sphere - which looks like a
> cheap hard-rubber bowling ball, or the foam they use in sofa cushions.  :D
> 
> Needs 0.2-0.3 more turbulence. ;)
> 
>> The granite pattern is (almost) correct (without the turbulence).
> 
> I don't know what you mean.
> 
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.

>> It also explains more comprehensively the original name: Mahogany. The
>> colour is similar to mahogany wood. Afaiac, I believe I should follow
>> that path in the first place and maybe disregard my own lighter version
>> (or not). Not sure yet. What do you think?
> 
> Well, there are myriad samples available at stonecontact-dot-com, all of which
> fall under the blanket/umbrella trade name of Dakota Mahogany and which have
> widely differing "color maps".
> 
I know. One of the problems is probably also that we do not know how 
much photoshopping has been applied to those photographs. However, I 
strongly believe that there is a link between the trade name and the 
deep hue of the mahogany wood. It would certainly help the sell.

> I think we need to alternate in our approach to this, and on the one hand try to
> formulaicly mimic the underlying patterns and sub-patterns, but on the other
> hand not forget that we can do some good ole' raytracing sleight-of-hand and do
> everything we can to fool the eye and mind into believing that they see
> something that is not there.
> 
Oh yes.

> One thing I thought of was to take a/some granite photos and run some
> edge-finding filters on them to see what pops out.
> 
> I'm curious about the rgb color mapping - the individual values - but also,
> given an individual grain region, what is the rgb variation across it?  How much
> secondary or tertiary pigment is patterned into the grain?
> 
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.

> Is there a way to estimate the grain sizes from the photos?  Or maybe there is
> statistical data in the literature?
> 
That is more difficult. Literature tells me that grain sizes range from 
microscopic to about 10-15mm in most cases and within the same granite, 
with sometimes larger minerals (phenocrysts) in the more porphyric 
varieties. See my answer to Mr.

> I ran across a neat conformal mapping image with circle packing that looked like
> a good mathematical way to get discrete regions with good grain-size variation.
> 
> AFAIK, we're using straight Perlin noise right now for granite.   Doing floor()
> on each of the axes produces the cells {} pattern.  I'm thinking if we could
> split the difference.... maybe with the step trick and/or select ()
> 
> Also need to keep in mind that the base pattern might just be a guide, and the
> final "look" is going to likely be a result of layering textures/materials.
> Hard to visualize.
> 
> And lastly, there were the brick pattern and random hexagon color threads that
> employed methods we might be able to use here.
> 
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.

>
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
> 

-- 
Thomas

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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

Post a reply to this message

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)

Post a reply to this message

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.

Post a reply to this message

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

Preview of image 'stepnoise.png'

"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/

Post a reply to this message

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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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)

Post a reply to this message

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

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

Post a reply to this message

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.

Post a reply to this message

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

Post a reply to this message

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

Post a reply to this message

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.
> 

I do not want to have you wait: This is the first render with StepNoise. 
My judgment is: perfection.

-- 
Thomas

Post a reply to this message

Attachments:
Download 'dakotagrains_sn_test.jpg' (92 KB)

Preview of image 'dakotagrains_sn_test.jpg'

hi,

Thomas de Groot <tho### [at] degrootorg> wrote:
> ... perfection.

"Flanders (medium) Gray".  :-)


regards, jr.

Post a reply to this message

Thomas de Groot <tho### [at] degrootorg> wrote:

> I do not want to have you wait: This is the first render with StepNoise.
> My judgment is: perfection.

.... holy crap!  :O

I would have never guessed it would THAT good!  Thanks for not making me wait.
That is indeed MUCH better than the turbulated cells experiment.  I'm glad that
it's panning out and we have something to work with as a good base pattern.

I'd say the next thing to do would be to have that texture be an entry in a
marble pattern texture_map, with a quartz texture as the vein.

After that, you're going to be the geological expert on whatever else might make
worthwhile additions.

Post a reply to this message

Quick stab at adding the vein.

Didn't like marble or planar, so I coded a Boolean math function for the stripe,
and let it blend on the sides.

Adding a mod to the function will repeat it, but it's too regular.
I tried warp {repeat x*4} but that repeats the whole pattern, and you get hard
lines.

I thought maybe I could layer it, but it's a pattern texture, and POV-Ray says
"No way!"

I also tried to add a specular highlight, and I'm too inept to get that to work
either.

Nor could I get the void created by using a difference to be anything but black.

It's unclear to me at the present time how to have separate turbulence values
for the stripe and the base StepNoise pattern, but I guess we'll figure that out
as we proceed.

Currently using the sum of two turbulated stripe patterns, so maybe the
placement of the stripes will have to be generated by a macro and an array of
plane offsets.

Anyway, this gives the general idea.

Post a reply to this message

Attachments:
Download 'granite_veins_1.png' (192 KB)

Preview of image 'granite_veins_1.png'

And the code:

Post a reply to this message

Attachments:
Download 'granite_veins_1.pov.txt' (4 KB)

Op 28/04/2021 om 17:47 schreef jr:
> hi,
> 
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> ... perfection.
> 
> "Flanders (medium) Gray".  :-)
> 
> 
> regards, jr.
> 

For the time being, yes ;-)

-- 
Thomas

Post a reply to this message

Op 28/04/2021 om 19:26 schreef Bald Eagle:
> Thomas de Groot <tho### [at] degrootorg> wrote:
> 
>> I do not want to have you wait: This is the first render with StepNoise.
>> My judgment is: perfection.
> 
> .... holy crap!  :O
> 
Indeed. Was what I thought too.

> I would have never guessed it would THAT good!  Thanks for not making me wait.
> That is indeed MUCH better than the turbulated cells experiment.  I'm glad that
> it's panning out and we have something to work with as a good base pattern.
> 
I still have to test the grain size control and such but we can indeed 
ditch the turbulated cells. I was happy and not happy at the same time 
with those; especially the larger grains were problematic.

> I'd say the next thing to do would be to have that texture be an entry in a
> marble pattern texture_map, with a quartz texture as the vein.
> 
Sure, and don't forget the quartz veins in the granite :-)

> After that, you're going to be the geological expert on whatever else might make
> worthwhile additions.
> 
Good. Work enough on the horizon.

-- 
Thomas

Post a reply to this message

Op 28/04/2021 om 22:37 schreef Bald Eagle:
> Quick stab at adding the vein.
> 
> Didn't like marble or planar, so I coded a Boolean math function for the stripe,
> and let it blend on the sides.
> 
My latest experiments with veins was by using agate and agate_turb as 
second texture layer. Needed to add a warp{turbulence *z} to hide the 
layering of agate. The results were promising if not perfect. I do not 
have an example render at hand at this moment.

> Adding a mod to the function will repeat it, but it's too regular.
> I tried warp {repeat x*4} but that repeats the whole pattern, and you get hard
> lines.
> 
> I thought maybe I could layer it, but it's a pattern texture, and POV-Ray says
> "No way!"
> 
> I also tried to add a specular highlight, and I'm too inept to get that to work
> either.
> 
> Nor could I get the void created by using a difference to be anything but black.
> 
> It's unclear to me at the present time how to have separate turbulence values
> for the stripe and the base StepNoise pattern, but I guess we'll figure that out
> as we proceed.
> 
It's a first step.

> Currently using the sum of two turbulated stripe patterns, so maybe the
> placement of the stripes will have to be generated by a macro and an array of
> plane offsets.
> 
> Anyway, this gives the general idea.
> 


-- 
Thomas

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Op 29/04/2021 om 03:17 schreef Bald Eagle:
> And the code:
> 

Thanks. Shall play with that too.

-- 
Thomas

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alright. Getting tired after a day of tweaking.

Second, overhauled, StepNoise version. Several things learned:

- to be careful with the /scale/ of the grains. This is as good as I 
dare to go. Larger minerals become increasingly unbelievable, so one 
needs to find the balance (as with the turbulated cells obviously, but 
StepNoise does a much better, although not perfect, job).

- the mask for the pigment_pattern needs a /very/ careful adjustment. 
The present one is good but could probably be improved further. Good 
enough for now.

- white grains are present but hardly visible. In the first version they 
were placed at the wrong place within the colour_map, rendering rings 
instead of mineral grains. Corrected that but need now to be enhanced a bit.

- sslt would probably increase realism, even in the frosted version. I 
am going to look into that.

-- 
Thomas

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Attachments:
Download 'dakotagrains_sn_test2.jpg' (95 KB)

Preview of image 'dakotagrains_sn_test2.jpg'

hi,

Thomas de Groot <tho### [at] degrootorg> wrote:
> alright. Getting tired after a day of tweaking.

glad you did though, "Flanders Gray (tm)" looks ready for turning into kitchen
worktops.  :-)  (am interested to see it being used other than in a
demo/reference image)


regards, jr.

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Thomas de Groot <tho### [at] degrootorg> wrote:
> alright. Getting tired after a day of tweaking.
>
> Second, overhauled, StepNoise version. Several things learned:
>
> - to be careful with the /scale/ of the grains. This is as good as I
> dare to go. Larger minerals become increasingly unbelievable, so one
> needs to find the balance (as with the turbulated cells obviously, but
> StepNoise does a much better, although not perfect, job).
>
> - the mask for the pigment_pattern needs a /very/ careful adjustment.
> The present one is good but could probably be improved further. Good
> enough for now.
>
> - white grains are present but hardly visible. In the first version they
> were placed at the wrong place within the colour_map, rendering rings
> instead of mineral grains. Corrected that but need now to be enhanced a bit.
>
> - sslt would probably increase realism, even in the frosted version. I
> am going to look into that.
>
> --
> Thomas

I am embarrassed to say that I can't see anything from that far. With respect to
that 10cm grid measures, I feel like you are no longer representing the same
rock? Did you work on it like that or with a closer camera? I do feel like
nothing is wrong with what little I see, though ! I have faith in you ! :-)

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Op 29-4-2021 om 19:21 schreef Mr:
> I am embarrassed to say that I can't see anything from that far. With respect to
> that 10cm grid measures, I feel like you are no longer representing the same
> rock? Did you work on it like that or with a closer camera? I do feel like
> nothing is wrong with what little I see, though ! I have faith in you ! :-)
> 
The 'problem' with changing patterns or pattern modifiers, is that 
scales get changed too. In a sense, you are right: it is not the same 
rock indeed and you need to readjust your frame of reference. Don't let 
it fool you: that 10cm grid does not represent anything real; I have 
always bee troubled by those quasi-real measurements (I am going to take 
out those cm-values and replace them by Martian Claw Units). My believe 
is that size/dimensions in POV-Ray are dimensionless as it were and only 
meaningful in relation to recognisable objects.

I attach a version with the material scaled by two. Still looking good, 
imo, and much better than the cells pattern.

-- 
Thomas

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Preview of image 'dakotagrains_sn_test3.jpg'

scaled by four; starting to break down I think, but still believable.

-- 
Thomas

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Preview of image 'dakotagrains_sn_test4.jpg'

Thomas de Groot <tho### [at] degrootorg> wrote:
> scaled by four; starting to break down I think, but still believable.

Have you tried doing a sequence of objects, with changing smooth-step thresholds
to see what effect that has?   There's also the amount of turbulence applied
which will affect how the underlying pattern looks.

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Op 30/04/2021 om 19:57 schreef Bald Eagle:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> scaled by four; starting to break down I think, but still believable.
> 
> Have you tried doing a sequence of objects, with changing smooth-step thresholds
> to see what effect that has?   There's also the amount of turbulence applied
> which will affect how the underlying pattern looks.
> 

Not yet, but good suggestion. Had something like that on my ToDo list. 
Want also to try sslt... and object-scale vs landscape-scale use... Too 
many balls in the air atm.

-- 
Thomas

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Op 29/04/2021 om 17:56 schreef jr:
> hi,
> 
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> alright. Getting tired after a day of tweaking.
> 
> glad you did though, "Flanders Gray (tm)" looks ready for turning into kitchen
> worktops.  :-)  (am interested to see it being used other than in a
> demo/reference image)
> 
I certainly agree with that. something is planned in that way.

-- 
Thomas

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hi,

Thomas de Groot <tho### [at] degrootorg> wrote:
> Op 29/04/2021 om 17:56 schreef jr:
> > ... (am interested to see it being used other than in a
> > demo/reference image)
> >
> I certainly agree with that. something is planned in that way.

personally, I'd love something .. surreal/"strange".  like a space station, or
perhaps that natty pre-war flatbed truck you used before, modelled in various
granites.  :-)


regards, jr.

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Op 1-5-2021 om 09:40 schreef jr:
> hi,
> 
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> Op 29/04/2021 om 17:56 schreef jr:
>>> ... (am interested to see it being used other than in a
>>> demo/reference image)
>>>
>> I certainly agree with that. something is planned in that way.
> 
> personally, I'd love something .. surreal/"strange".  like a space station, or
> perhaps that natty pre-war flatbed truck you used before, modelled in various
> granites.  :-)
> 
Oh lol! That last one would be interesting! I shall see what I can do.

I was thinking, among other things, about the El Capitan half dome...
https://en.wikipedia.org/wiki/El_Capitan

Note that granitic landscapes/formations look rather featureless as far 
as textures are concerned. They have no/little internal layering, and 
weathering is mostly 'rounding' the rocks.

-- 
Thomas

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hi,

Thomas de Groot <tho### [at] degrootorg> wrote:
> Op 1-5-2021 om 09:40 schreef jr:
> > Thomas de Groot <tho### [at] degrootorg> wrote:
> >> Op 29/04/2021 om 17:56 schreef jr:
> >>> ... (am interested to see it being used other than in a
> >>> demo/reference image)
> >>>
> >> I certainly agree with that. something is planned in that way.
> >
> > personally, I'd love something .. surreal/"strange".  like a space station, or

incongruous rather than strange.


> > perhaps that natty pre-war flatbed truck you used before, modelled in various
> > granites.  :-)
> >
> Oh lol! That last one would be interesting! I shall see what I can do.

uh, nice.


> I was thinking, among other things, about the El Capitan half dome...
> https://en.wikipedia.org/wiki/El_Capitan
>
> Note that granitic landscapes/formations look rather featureless as far
> as textures are concerned. They have no/little internal layering, and
> weathering is mostly 'rounding' the rocks.

had not heard of 'El Capitan' before.  900+ metres of sheer cliff, just .. wow.
 cannot really imagine, but feel one would feel distinctly ant-sized standing at
its base.  (America, huh?  _everything_ is big in America!  :-))


regards, jr.

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Op 01/05/2021 om 17:22 schreef jr:
> hi,
> 
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> I was thinking, among other things, about the El Capitan half dome...
>> https://en.wikipedia.org/wiki/El_Capitan
>>
>> Note that granitic landscapes/formations look rather featureless as far
>> as textures are concerned. They have no/little internal layering, and
>> weathering is mostly 'rounding' the rocks.
> 
> had not heard of 'El Capitan' before.  900+ metres of sheer cliff, just .. wow.
>   cannot really imagine, but feel one would feel distinctly ant-sized standing at
> its base.  (America, huh?  _everything_ is big in America!  :-))
> 
Closer to home (Europe) the cores of the Alps are granites. Bretagne, 
Scandinavia and Scotland are also ancient mountain range cores were 
granites are common.

-- 
Thomas

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hi,

Thomas de Groot <tho### [at] degrootorg> wrote:
> Op 01/05/2021 om 17:22 schreef jr:
> > ...
> Closer to home (Europe) the cores of the Alps are granites. Bretagne,
> Scandinavia and Scotland are also ancient mountain range cores were
> granites are common.

in Aberdeen it's in the "moniker" - "granite city".
<https://en.wikipedia.org/wiki/Aberdeen#Landmarks>


regards, jr.

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Op 2-5-2021 om 11:10 schreef jr:
> hi,
> 
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> Op 01/05/2021 om 17:22 schreef jr:
>>> ...
>> Closer to home (Europe) the cores of the Alps are granites. Bretagne,
>> Scandinavia and Scotland are also ancient mountain range cores were
>> granites are common.
> 
> in Aberdeen it's in the "moniker" - "granite city".
> <https://en.wikipedia.org/wiki/Aberdeen#Landmarks>
> 
I didn't know that :-)

You may be interested, like others, now that we are concentrating on 
granites (and other rocks) as used in monuments, by the following text I 
came across on the web today:

https://www.ucl.ac.uk/earth-sciences/sites/earth-sciences/files/earth_sciences_geotrail_graveyard_geology.pdf

Very instructive reading indeed.

-- 
Thomas

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Op 30-4-2021 om 19:57 schreef Bald Eagle:
> Have you tried doing a sequence of objects, with changing smooth-step thresholds
> to see what effect that has?   There's also the amount of turbulence applied
> which will affect how the underlying pattern looks.
> 

Attached a set of step noise patterned granites. Variations of the 
turbulence value just changes the distribution of the different grains. 
Most interesting is the use (1) of the turbulence within a warp{} 
pattern and (2) the use of, especially, octaves, lambda, and omega 
values. Thus, the two last renders on the bottom row, produce the best 
granite pattern, imo.

-- 
Thomas

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Attachments:
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Preview of image 'stepnoise_granites.jpg'

Finally, using a blending technique developed by Tekno Frannansa, The 
attached granite, based on the latest preceding one, looks also the most 
natural!

-- 
Thomas

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Preview of image 'dakotagrains_test_sn7.jpg'

For your judgment again.

A weathered, granite, boulder has been hit at and a piece broke off.

Inside: the latest version with warp {turbulence Turbulence octaves 2 
lambda 1 omega 2}

Outside: the blurred/blended version of the above

-- 
Thomas

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Preview of image 'granitetest.jpg'

Thomas de Groot <tho### [at] degrootorg> wrote:
> Finally, using a blending technique developed by Tekno Frannansa, The
> attached granite, based on the latest preceding one, looks also the most
> natural!
>
> --
> Thomas

Hi! I could imagine it for an outdoor landscape. But for other closer framed
use, I presently can't say that I prefer it over the other results so far:

Something still feels "blurry" about it. Sorry to be that vague. I still believe
it could be due to something default in the specular component / or maybe the
camera has aperture? / or there is just no normal bump distortion at all which
could suffice to lead to this perceived lack  of contrast?

At this stage, to properly evaluate the patterns, a close up 1000+ px side
render from less than 1 meter distance and more than 10 cm area visible carrying
your graduated floor now really seems absolutely necessary to see anything.

I feel like I'm spoiling myself a movie by looking at it from a phone streamed
screener file :-D

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Op 3-5-2021 om 17:10 schreef Mr:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> Finally, using a blending technique developed by Tekno Frannansa, The
>> attached granite, based on the latest preceding one, looks also the most
>> natural!
>>
>> --
>> Thomas
> 
> Hi! I could imagine it for an outdoor landscape. But for other closer framed
> use, I presently can't say that I prefer it over the other results so far:
> 
> Something still feels "blurry" about it. Sorry to be that vague. I still believe
> it could be due to something default in the specular component / or maybe the
> camera has aperture? / or there is just no normal bump distortion at all which
> could suffice to lead to this perceived lack  of contrast?
> 
I am afraid you need to be more explicit because I do not really 
understand. What is blurry here? I see rather /crisp/ minerals in a 
random pattern. Maybe I should post the code? you could test it better I 
suppose.

> At this stage, to properly evaluate the patterns, a close up 1000+ px side
> render from less than 1 meter distance and more than 10 cm area visible carrying
> your graduated floor now really seems absolutely necessary to see anything.
> 
I truly cannot imagine what you can gain by such a render. What are you 
looking for exactly? If I do what you say, you will see a bunch of 
coloured pixels, or am I thinking in the wrong direction?

> I feel like I'm spoiling myself a movie by looking at it from a phone streamed
> screener file :-D
> 
That would be a sorry business indeed. However, I still wonder /what/ 
you see exactly (or do not see)...


-- 
Thomas

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Thomas de Groot <tho### [at] degrootorg> wrote:
> For your judgment again.

This is pretty spectacular, as was the prior ovus example.

I think what Maurice is trying to point out is the "frosted" look of the blurred
pattern.
I think the earlier prototype StepNoise example was more impressive than the
current iteration.
And I'm not sure why you chose to do several experiments with start and end both
equal to 0.5 - as that is just the cells pattern.

But I must say that I really like this frosted look for an outdoor, weathered
piece of natural stone, as this is really what it looks like, with dust, and
evaporated rain, and pollen, etc.  Adding that displacement or normal really
gives it that natural look as well.

I think Maurice is looking for that lack of micro-surface texture that leads to
a lot of air - which has a different ior than the minerals and leads to that dry
paper / freshly applied transparent tape look.  Polishing, wetting, and waxing
gives it that sharp, crisp, high-contrast look with more saturated colors and
clearer delineations between the grains.

At least that's what I'm speculating.

However, all in all, this is very pleasing, and extremely encouraging progress!

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A few more comments:

Op 03/05/2021 om 17:10 schreef Mr:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> Finally, using a blending technique developed by Tekno Frannansa, The
>> attached granite, based on the latest preceding one, looks also the most
>> natural!
>>
>> --
>> Thomas
> 
> Hi! I could imagine it for an outdoor landscape. But for other closer framed
> use, I presently can't say that I prefer it over the other results so far:
> 
Yes. Please note that the "blended" cells texture /is/ for the 
weathered, outdoor, aspect of any granitic rock you may come across. The 
"fresh" look is when such a boulder is broken. For granitic landscapes, 
this texture /as is/ would not be convenient and a much simpler one 
should replace it, for instance something based on one of those 
landscape textures created by Jaime Vives Piqueres.

Anyway, a combination of "weathered" and "fresh" is shown in my image 
GraniteTest.jpg, posted a bit earlier.

> Something still feels "blurry" about it. Sorry to be that vague. I still believe
> it could be due to something default in the specular component / or maybe the
> camera has aperture? / or there is just no normal bump distortion at all which
> could suffice to lead to this perceived lack  of contrast?
> 
Nothing of the sort I believe. The camera is a standard one (no 
aperture) but the environment is just a white featureless space. Maybe 
that is causing your "lack of contrast"?

As for the finish, the following is used (based on code provided by Ive):

//start code---------------------------------------------
   #macro Dull_Highlights()
     specular 0.05
     roughness 0.1
   #end

       finish {	//frosted version
         diffuse albedo 0.6 brilliance 1.5
         Dull_Highlights() // a small amount of highlights for realism
       }
//end code---------------------------------------------


> At this stage, to properly evaluate the patterns, a close up 1000+ px side
> render from less than 1 meter distance and more than 10 cm area visible carrying
> your graduated floor now really seems absolutely necessary to see anything.
> 
I shall render a 2048x2048 px "fresh" granite image today. Don't be 
surprised: it is not really believable any more as a granite, but it may 
generate comments towards a better code, and that is ultimately, the 
purpose of this exercise.

> I feel like I'm spoiling myself a movie by looking at it from a phone streamed
> screener file :-D
> 


-- 
Thomas

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