POV-Ray : Newsgroups : povray.binaries.images : Granites Intermezzo : Re: Granites Intermezzo Server Time
15 May 2021 20:51:01 EDT (-0400)
  Re: Granites Intermezzo  
From: Thomas de Groot
Date: 26 Apr 2021 02:28:30
Message: <60865d8e$1@news.povray.org>
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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