"And" <49341109@ntnu.edu.tw> wrote:
> "Bald Eagle" <cre### [at] netscapenet> wrote:
> > "And" <49341109@ntnu.edu.tw> wrote:
> >
> > I didn't read this paper (yet), but it just showed up in my email inbox.
> > Maybe it will inspire some ideas, serve as an entry to other similar research
> > papers, and be of some practical use in developing your challenging project.
> >
> > (I hadn't thought of using L-systems!)
> >
> > -BW
> >
> >
>
>
> Oh, ... I wouldn't like to make any detailed tree trunk "3D Model"(that is
> another
> challenge), I just generate a (3D)texture. I implement my texture in POV-Ray,
> outputting "pigment {...}" as its final form.

Naturally.  The wood pigment patterns we've almost all been using for the past
30 years are just a bunch of concentric cylindrical rings.   Seems to work well
enough for most purposes.
To add a bit of realism by simulating the cross-section of those 3D branches,
the black hole warp can be used, and that's what I was thinking when I suggested
looking this over - not copying the paper's method verbatim.

So rather than create a whole 3D tree and then slice it (which would necessarily
limit the pattern to the locus of the individually modeled tree), I was thinking
that you could assemble a pattern of black hole warps using an L-system in code,
which would then be used to define the pigment {}.

I my mind, this would be very much like the way Tor Olav Kristensen uses a macro
to assemble the terms of a long Bernstein polynomial function.

jr has also done a lot of development using the method of including the parsed
text of temporary files to assemble complex data/code structures, as well as
some pretty complex data "trees" - which might serve as inspiration to you or
others for generating complex pigment pattern definitions.

TdG may have code of a similar nature in his vast archive, or have other ideas
of his own about how to approach the branch/knot aspect of the wood pattern.

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Op 23/08/2022 om 12:52 schreef Bald Eagle:
> TdG may have code of a similar nature in his vast archive, or have other ideas
> of his own about how to approach the branch/knot aspect of the wood pattern.
> 

Not really. The best I can come up with is isowood by Christoph Hormann

http://www.imagico.de/iso_wood_en.php

Dan Hentschel and Nicolas Rougier did a couple of wood textures some 15 
years ago, Nicolas using black hole warps.

Warp has some interesting things to say, about wood, incidentally

http://warp.povusers.org/povtips/


-- 
Thomas

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"Bald Eagle" <cre### [at] netscapenet> wrote:
> "And" <49341109@ntnu.edu.tw> wrote:
> >
> > Oh, ... I wouldn't like to make any detailed tree trunk "3D Model"(that is
> > another
> > challenge), I just generate a (3D)texture. I implement my texture in POV-Ray,
> > outputting "pigment {...}" as its final form.
>
> Naturally.  The wood pigment patterns we've almost all been using for the past
> 30 years are just a bunch of concentric cylindrical rings.   Seems to work well
> enough for most purposes.
> To add a bit of realism by simulating the cross-section of those 3D branches,
> the black hole warp can be used, and that's what I was thinking when I suggested
> looking this over - not copying the paper's method verbatim.
>
> So rather than create a whole 3D tree and then slice it (which would necessarily
> limit the pattern to the locus of the individually modeled tree), I was thinking
> that you could assemble a pattern of black hole warps using an L-system in code,
> which would then be used to define the pigment {}.

I just notice "black hole warps" this time. It seems it is a 'spherical'
distortion around a sphere-center?

However, I can make more natural knot shape by myself. I use function as pigment
input, it is more flexible than the built-in pigment-warp of POV-Ray. I still
need several months to integrate it with my GUI java program. But I will
investigate this feature(black_hole warp) for it being a convenient effect.


>
> I my mind, this would be very much like the way Tor Olav Kristensen uses a macro
> to assemble the terms of a long Bernstein polynomial function.
>

'Bernstein polynomial function' looks like some special function I know, but I
don't know this one.


> jr has also done a lot of development using the method of including the parsed
> text of temporary files to assemble complex data/code structures, as well as
> some pretty complex data "trees" - which might serve as inspiration to you or
> others for generating complex pigment pattern definitions.

Oh, jr had e-mail me and told me something, thereby I fix the 'locale' problem
of number quickly last time.


>
> TdG may have code of a similar nature in his vast archive, or have other ideas
> of his own about how to approach the branch/knot aspect of the wood pattern.

Post a reply to this message

Thomas de Groot <tho### [at] degrootorg> wrote:
> Op 23/08/2022 om 12:52 schreef Bald Eagle:
> > TdG may have code of a similar nature in his vast archive, or have other ideas
> > of his own about how to approach the branch/knot aspect of the wood pattern.
> >
>
> Not really. The best I can come up with is isowood by Christoph Hormann
>
> http://www.imagico.de/iso_wood_en.php
>
> Dan Hentschel and Nicolas Rougier did a couple of wood textures some 15
> years ago, Nicolas using black hole warps.
>
> Warp has some interesting things to say, about wood, incidentally
>
> http://warp.povusers.org/povtips/
>
>
> --
> Thomas

I visited Christoph Hormann's site long time ago. I have clear impression of it
by the natural wood appearance and color.
I know it use 'isosurface', not simple texture.

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I got several wood plunk 2~3 weeks ago from my grandmother's furnitures. She is
just pass away one month ago.
I collect some of the wood, look them and thinking. So far I feel I have
collected enough idea of my wood texture generator program I want to make.

I sign up a computer lesson to learn spring framework (about Java programming
languish) September. If everything well, I will rewrite some component(with Java
program) after learning that lesson.
I wish the wood texture program become sufficient good after developing.

I have found some good method to generate bumps associate pattern for making
complex pattern these days. So I'm preparing.

But I need some career planing (suggestion, ...), too. Because I delay something
important on my life again and again...

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Attachments:
Download 'dsc_0814.jpg' (745 KB)

Preview of image 'dsc_0814.jpg'

And then, anyone know why the wood grains becomes so white(or ever saw the same
) on my last post image(dsc_0814)? I don't know why.

------------------------------------------------------------------
If I can simulate the most of the wood pattern detail like this attached pic
(the
desk has been thrown away...) one day, my program will be valuable.
------------------------------------------------------------------

In the future I need to learn something about call/invoke POV-Ray in another
program.

I have many reasons.
The one reason is that I need correct information about the f_bumps pattern.
Another is preview, but not only preview.

Post a reply to this message

Attachments:
Download 'dsc_1003.jpg' (929 KB)

Preview of image 'dsc_1003.jpg'

"And" <49341109@ntnu.edu.tw> wrote:
> And then, anyone know why the wood grains becomes so white(or ever saw the same
> ) on my last post image(dsc_0814)? I don't know why.

What you're seeing there is oxidation of the paint, or a frosting or "bloom"
from when solvent gets on the surface and dissolves out some of the clear
binder, or when water gets on the paint and hydrates/swells the surface coating,
which I believe causes it to develop microscopic cracks, allowing air in, and
giving it a different IOR.
Kind of like taking transparent tape and putting it on a dark surface - it's not
transparent until you rub/burnish it down to exclude all of the air between the
tape and the surface.

> ------------------------------------------------------------------
> If I can simulate the most of the wood pattern detail like this attached pic

I think that what might have to happen is to have a variety of functions that
get interpolated across the surface of the wood, to give rise to a smooth
blending of different patterns.   Right now you're just sort of unioning them.

> I have many reasons.
> The one reason is that I need correct information about the f_bumps pattern.

What needs to be corrected?

- BW

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"Bald Eagle" <cre### [at] netscapenet> wrote:
> "And" <49341109@ntnu.edu.tw> wrote:
> > And then, anyone know why the wood grains becomes so white(or ever saw the same
> > ) on my last post image(dsc_0814)? I don't know why.
>
> What you're seeing there is oxidation of the paint, or a frosting or "bloom"
> from when solvent gets on the surface and dissolves out some of the clear
> binder, or when water gets on the paint and hydrates/swells the surface coating,
> which I believe causes it to develop microscopic cracks, allowing air in, and
> giving it a different IOR.
> Kind of like taking transparent tape and putting it on a dark surface - it's not
> transparent until you rub/burnish it down to exclude all of the air between the
> tape and the surface.

Wow!
Are you an expert of chemical?

>
> > ------------------------------------------------------------------
> > If I can simulate the most of the wood pattern detail like this attached pic
>
> I think that what might have to happen is to have a variety of functions that
> get interpolated across the surface of the wood, to give rise to a smooth
> blending of different patterns.   Right now you're just sort of unioning them.
>
> > I have many reasons.
> > The one reason is that I need correct information about the f_bumps pattern.
>
> What needs to be corrected?

Because I found many beautiful pattern this week, including something
radial-randomize or circular-randomize bump pattern. They are useful and play an
important role.
Maybe my program can automatically pick them(the parameter of control where the
large-value color-block appear), fitting the shape of the woodgrain
angular-shape curve you make. I think maybe they have relation...

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"And" <49341109@ntnu.edu.tw> wrote:

> Wow!
> Are you an expert of chemical?

Sorta.  I have a chemistry degree, went to pharmacy school, and did most of a
PhD in Organic Chemistry and Mechanistic Enzymology.

But the real practical knowledge of that stuff comes from knowing people who
work with and restore antiques (million-dollar board-room table type things),
and working with professional painters.

There are a lot of great furniture restoration channels on YouTube that I'm sure
would cover some of what happens to finishes and what can be done to
repair/restore them.


> Maybe my program can automatically pick them(the parameter of control where the
> large-value color-block appear), fitting the shape of the woodgrain
> angular-shape curve you make. I think maybe they have relation...

Perhaps TOK or Bill Pokorny might have some ideas.
There may be some useful code in the newsgroup archives from people like Tek,
Zeger Knaepen, and other who have written mind-bogglingly complex code.
Also, you should check out the Shadertoy website and see how people are coding
their patterns, since it will let you see how they build very complex patterns
from a collection of much simpler equations.
It might also be worth contacting Martijn Steinrucker (Art of Code) or Inigo
Quilez to see if they have any ideas for how to model a really excellent and
realistic wood-grain pattern.

- BW

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I have to tell you, this is a tough problem, to make a fully procedural wood
texture.

I think a lot of things have to be "fixed" in order to get good results - like
color-map cycling, the behaviour of the modulo operator across the origin, and
the domain of user generated functions.

I got a very rough simulation, but it's a layered texture, to get the checking
(cracks) and spalting.

To get a better wood, there would have to be knots and burls in 3D so that it
could also be used as an isosurface.

- BW

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Attachments:
Download 'radialfunctions.png' (322 KB)

Preview of image 'radialfunctions.png'