POV-Ray : Newsgroups : povray.binaries.images : Alum Server Time
26 Sep 2022 08:33:51 EDT (-0400)
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From: Paolo Gibellini
Subject: Re: Alum
Date: 20 Sep 2021 15:25:06
Message: <6148e012@news.povray.org>
Il 20/09/2021 01:09, Samuel B. ha scritto:
 > Hi,
 >
 > Here's an alum crystal.
 >
 > The face data (including HKL, distance and colors [not used]) were 
copied from
 > KrystalShaper and converted to an array-ready format thanks to a 
couple of find
 > & replace operations in notepad++. Because the data works with the cubic
 > crystalline system, they were easily converted into plane normals and 
offsets.
 > The planes were then used in an intersection object. 50 faces total. No
 > light_sources are present in the scene; just reflections.
 >
 > (If anyone's wondering why I don't simply export POV-Ray files from
 > KrystalShaper, it's because in the future I intend to have more 
customization
 > options for certain faces.)
 >


This image is poetic, Sam!

Paolo


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From: William F Pokorny
Subject: Re: Alum
Date: 21 Sep 2021 11:42:44
Message: <6149fd74$1@news.povray.org>
On 9/19/21 7:09 PM, Samuel B. wrote:
> Here's the source code (minus luminous bloom):

Cool. Thank you for posting the code.

I used your scene to do a little crude bench-marking of my povr branch.

To create the attached image, I changed:

#declare RGBSun = srgb 1.3*<2, 1.99, 1.97>;

to

#declare RGBSun = srgb <1, 0.99, 0.97>;
#declare RGBSun = 2.7*RGBSun;

because my povr branch now doesn't allow srgb channel specifications 
outside the 0-1 range.

Plus, I changed the crystal's normal to the povr branch's quilted normal 
- but still scaled very small - and aiming for a blurred reflection.

Given you are using camera blur to over sample, I wanted to see how 
povr's big jitter would compare time wise. The big jitter approach took 
2.4x longer to render at +a0.0 +am2 +r4 +j62.111 than your blur samples 
method of oversampling. I can tell from the render statistics I was too 
aggressive at r4 - as I shot roughly 2.7x more rays. I'd say the mothods 
are in the ballpark performance wise, with other differences in control 
and result which might matter or not. FWIW.

Bill P.


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Attachments:
Download 'sam_.jpg' (47 KB)

Preview of image 'sam_.jpg'
sam_.jpg


 

From: Samuel B 
Subject: Re: Alum
Date: 21 Sep 2021 19:50:00
Message: <web.614a6f11cca1de15cb705ca46e741498@news.povray.org>
Alain Martel <kua### [at] videotronca> wrote:
> generate PNG images by default.
> Those two switches are default values since version 3.7.
> +a0.3 is also the default when antialiasing is used.

I know some things are enabled by default, but I like to include all the options
that I plan to change later on... because I'm lazy :D

> The default of +r3 gives you better results.

True that, but +r1 is faster and better than no antialiasing at all, imo. (It
lends a softer look to the rendering.)

> Use the complement of your colour. That's 1 minus the desired colour.

Thanks, Alain. I originally used fade_color and supporting statements, but the
color was becoming too saturated. So I cheaped out instead, which is
regrettable. Because by doing so, I only managed to simulate surface dyes, which
are highly frowned upon in the mineral community ;)

Sam


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From: Samuel B 
Subject: Re: Alum
Date: 21 Sep 2021 19:50:00
Message: <web.614a6f30cca1de15cb705ca46e741498@news.povray.org>
Paolo Gibellini <p.g### [at] gmailcom> wrote:
> Il 20/09/2021 01:09, Samuel B. ha scritto:
>  > Here's an alum crystal.
>
> This image is poetic, Sam!

Thanks Paolo!

Sam


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From: Samuel B 
Subject: Re: Alum
Date: 21 Sep 2021 20:10:00
Message: <web.614a733fcca1de15cb705ca46e741498@news.povray.org>
William F Pokorny <ano### [at] anonymousorg> wrote:
> On 9/19/21 7:09 PM, Samuel B. wrote:
> > Here's the source code (minus luminous bloom):
>
> Cool. Thank you for posting the code.
>
> I used your scene to do a little crude bench-marking of my povr branch.

Thanks, Bill. Is there a binary of povr for Windows, or am I just not seeing it?

> To create the attached image, I changed:
>
> #declare RGBSun = srgb 1.3*<2, 1.99, 1.97>;
>
> to
>
> #declare RGBSun = srgb <1, 0.99, 0.97>;
> #declare RGBSun = 2.7*RGBSun;
>
> because my povr branch now doesn't allow srgb channel specifications
> outside the 0-1 range.

Is that why the image is darker overall? (Why the clamping, btw?)

> Plus, I changed the crystal's normal to the povr branch's quilted normal
> - but still scaled very small - and aiming for a blurred reflection.

Right away I can see that the quilted pattern seems superior in this instance.
The reflection on the plane starts out much sharper, whereas the granite pattern
I used starts out way too blurry.

> Given you are using camera blur to over sample, I wanted to see how
> povr's big jitter would compare time wise. The big jitter approach took
> 2.4x longer to render at +a0.0 +am2 +r4 +j62.111 than your blur samples
> method of oversampling. I can tell from the render statistics I was too
> aggressive at r4 - as I shot roughly 2.7x more rays. I'd say the mothods
> are in the ballpark performance wise, with other differences in control
> and result which might matter or not. FWIW.

The blur is exaggerated in your render compared to mine, so perhaps the
performance would be more comparative with a reduced bump_size and lower +r
value?

Sam


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From: William F Pokorny
Subject: Re: Alum
Date: 22 Sep 2021 04:27:05
Message: <614ae8d9$1@news.povray.org>
On 9/21/21 8:05 PM, Samuel B. wrote:
> ... Is there a binary of povr for Windows, or am I just not seeing it?

No, it's a linux / unix / macos only effort. I don't use windows.

Further, I only once in a while publish a tarball(1) that you currently 
have to compile yourself. I've not yet gotten to what I want to be my 
initial, public, git repository. It's my playpen, but hope some find 
bits of the play/work useful.

(1) - To povray.binaries.programming

>> because my povr branch now doesn't allow srgb channel specifications
>> outside the 0-1 range.
> Is that why the image is darker overall? 
Yes.

(Why the clamping, btw?)

It isn't about clamping values, but rather restricting the srgb* keyword 
use to values which make sense. There is an underlying equation - and it 
runs for any input channel value - but only values in the [0..1] range 
make sense.

//--- Limit srgb use to [0..1] range!
#version 3.8;
global_settings {assumed_gamma 1.0}

#declare RGBSun  = srgb 1.30*<2, 1.99, 1.97>;
#declare RGBSun_0 = rgb 1.30*<2, 1.99, 1.97>;
#declare RGBSun_1 = rgb 4.58*<2, 1.99, 1.97>;
#declare RGBSun_2 = srgb <2.0, 0.9, 0.8>;
#declare RGBSun_3 = srgb <2.0,-0.9,-1.8>;

#declare SRGBSun  = srgb <1.0, 0.45, 0.4>;
#declare RGBSun_4 = 9.16*SRGBSun;

#debug "\n"
#debug concat("srgb 1.30*<2, 1.99, 1.97> = rgb <",
     vstr(3,RGBSun,",", 0,-1),">\n")
#debug concat("rgb  1.30*<2, 1.99, 1.97> = rgb <",
     vstr(3,RGBSun_0,",", 0,-1),">\n")
#debug concat("rgb  4.58*<2, 1.99, 1.97> = rgb <",
     vstr(3,RGBSun_1,",", 0,-1),">\n")
#debug concat("srgb      <2.0, 0.9, 0.8> = rgb <",
     vstr(3,RGBSun_2,",", 0,-1),">\n")
#debug concat("srgb      <2.0,-0.9,-1.8> = rgb <",
     vstr(3,RGBSun_3,",", 0,-1),">\n")
#debug "\n"
#debug concat("9.16*SRGBSun              = rgb <",
     vstr(3,RGBSun_4,",", 0,-1),">\n")
#debug "\n"

#error "Parsing test. Stop early."
//---

> The blur is exaggerated in your render compared to mine, so perhaps the
> performance would be more comparative with a reduced bump_size and lower +r
> value?
Yes, I expect you are correct.

Attaching another image. Here playing with one of the prototype normal 
patterns in povr's bevy normal wrapper. It's kind of a non-drifting(1) 
wrinkles rotation about a specified axis (or was it toward a point...). 
Anyhow, it's perturbing/mangling the normal and for the image use a 
negative bump to intentionally 'sometimes' invert the normals. Doesn't 
represent anything real, but I think it looks neat! :-)

(1) - Elsewhere I posted about our current "normal wrinkles pattern bias."

Bill P.


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Attachments:
Download 'sam_bevy_normal_6_negbmp.jpg' (49 KB)

Preview of image 'sam_bevy_normal_6_negbmp.jpg'
sam_bevy_normal_6_negbmp.jpg


 

From: Alain Martel
Subject: Re: Alum
Date: 22 Sep 2021 12:38:50
Message: <614b5c1a$1@news.povray.org>


> Thanks, Alain. I originally used fade_color and supporting statements, but the
> color was becoming too saturated. So I cheaped out instead, which is
> regrettable. Because by doing so, I only managed to simulate surface dyes, which
> are highly frowned upon in the mineral community ;)
> 
> Sam
> 

If your colour get to saturated, that mean that your fade_distance is to 
short, so, just increase fade_distance as needed.
Also, to get realistic results, fade_power need to be 1001 or 1, not 2.


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From: Samuel B 
Subject: Re: Alum
Date: 23 Sep 2021 18:45:00
Message: <web.614d022acca1de15cb705ca46e741498@news.povray.org>
William F Pokorny <ano### [at] anonymousorg> wrote:
> On 9/21/21 8:05 PM, Samuel B. wrote:
> > ... Is there a binary of povr for Windows, or am I just not seeing it?
>
> No, it's a linux / unix / macos only effort. I don't use windows.

Oh well. I don't blame anyone for not using Windows... Not only do we have to
pay for a license, but we're now stuck with mandatory updates whenever M$
decides it needs the community to bug test its code (which is several times a
year). (I've been thinking of eventually jumping ship to Linux. From what I
hear, compatibility with Steam games is high thanks to Proton, meaning I have
fewer reasons than ever to abandon ship.)

> Further, I only once in a while publish a tarball(1) that you currently
> have to compile yourself. (...)

Well, I won't be attempting to compile it on Windows any time soon. It would
probably require Visual Studio. I tried downloading the free version a while
back, and what an outdated, over-bloated piece of work it was, imo :S

> (Why the clamping, btw?)
>
> It isn't about clamping values, but rather restricting the srgb* keyword
> use to values which make sense. There is an underlying equation - and it
> runs for any input channel value - but only values in the [0..1] range
> make sense.

I'm still not sure I understand. Does the equation restrict values due to its
very nature? Or did you impose a restriction so that it doesn't produce
nonsense?

> > The blur is exaggerated in your render compared to mine, so perhaps the
> > performance would be more comparative with a reduced bump_size and lower +r
> > value?
>
> Yes, I expect you are correct.
>
> Attaching another image. Here playing with one of the prototype normal
> patterns in povr's bevy normal wrapper. It's kind of a non-drifting(1)
> wrinkles rotation about a specified axis (or was it toward a point...).
> Anyhow, it's perturbing/mangling the normal and for the image use a
> negative bump to intentionally 'sometimes' invert the normals. Doesn't
> represent anything real, but I think it looks neat! :-)

Lots of interesting patterns in there, but I can't help but to notice that the
bright interior reflections on the lower left portion are gone.

Sam


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From: Samuel B 
Subject: Re: Alum
Date: 23 Sep 2021 18:45:00
Message: <web.614d02dccca1de15cb705ca46e741498@news.povray.org>
Alain Martel <kua### [at] videotronca> wrote:
> > (...) I originally used fade_color and supporting statements, but the
> > color was becoming too saturated. (...)
>
> If your colour get to saturated, that mean that your fade_distance is to
> short, so, just increase fade_distance as needed.
> Also, to get realistic results, fade_power need to be 1001 or 1, not 2.

That was probably the issue. I should have just kept the fade_color and added a
colorless absorbing media which would have probably made it look right.
Something to keep in mind for the next render.

Sam


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From: William F Pokorny
Subject: Re: Alum
Date: 24 Sep 2021 11:41:02
Message: <614df18e$1@news.povray.org>
On 9/23/21 6:39 PM, Samuel B. wrote:
> I'm still not sure I understand. Does the equation restrict values due to its
> very nature? 

Well on the negative side sort of, maybe. Generally, I'd say the srgb 
decode equation mangles values outside the zero to one range making it 
hard to control - to get what you want and too easy to not get what you 
want.

> Or did you impose a restriction so that it doesn't produce
> nonsense?

Yes. I think it better users make use of rgb* keywords, where they want 
to work with values outside the 0-1 range so povr forces this.

Bill P.


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