"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'

"Bald Eagle" <cre### [at] netscapenet> wrote:
> I have to tell you, this is a tough problem, to make a fully procedural wood
> texture.
>

No no...
Make a fully procedural wood texture is interesting to me. It is keep my
attention these days.

> 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 solved color-map cycling by creating main part of pigment (using function) ,
such function change its value from 0~1~0 every year. It has been done, so I
don't concern it anymore.

"The domain of user generated function" means I needs provide something flexible
for user to apply their own function. Before that time I can offer the standard
function which I developed.


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

How do you get such black 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


I will add knots in my output pigment pattern when I prepare enough code. But
they are just pattern, not a 3D shape.

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

> How do you get such black spalting?

#declare Crack1 =
color_map {
 [0.00 rgb 1]
 [0.50 rgb 1]
 [0.50 rgb 0]
 [0.55 rgb 0]
 [0.51 rgb 1]
 [1.00 rgb 1]
}

#declare Spalting = function {pigment {leopard turbulence 1 color_map {Crack1}}}

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I think I should learn Javafx first to rewrite it. My knowledge of design
program is not enough.

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"And" <49341109@ntnu.edu.tw> wrote:
> I think I should learn Javafx first to rewrite it. My knowledge of design
> program is not enough.

Here's a dispersion pattern I found that seems to also make a good wood ring
pattern.

https://en.wikipedia.org/wiki/Dispersion_(water_waves)#Dispersion_relation
https://www.desmos.com/calculator/dzrqmexxik

#declare T_wave = 0.5; // -10 to 10 in example
#declare FWave1 = function {sum (k_wave, 0.3, 3, mod ( (sqrt(x*x+y*y) - sqrt
(9.81*k_wave*3)*T_wave)*k_wave*3, 2*pi) <= 1)}
#declare FWave2 = function {sum (k_wave, 0.3, 3, abs ( (sqrt(x*x+y*y) - sqrt
(9.81*k_wave*3)*T_wave)*k_wave*3) <= 0.3)}
#declare Formula201 = function {(FWave1 (x, y, z) + FWave2 (x, y, z))/2}

plane {z, 0 pigment {function {Formula201 (x,y,z)} } }

Add 2 different color maps for light and dark wood, and it should look a lot
better.

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Attachments:
Download 'mathpatterns1.png' (334 KB)

Preview of image 'mathpatterns1.png'

"Bald Eagle" <cre### [at] netscapenet> wrote:
> Here's a dispersion pattern I found that seems to also make a good wood ring
> pattern.
>
> https://en.wikipedia.org/wiki/Dispersion_(water_waves)#Dispersion_relation
> https://www.desmos.com/calculator/dzrqmexxik
>
> #declare T_wave = 0.5; // -10 to 10 in example
> #declare FWave1 = function {sum (k_wave, 0.3, 3, mod ( (sqrt(x*x+y*y) - sqrt
> (9.81*k_wave*3)*T_wave)*k_wave*3, 2*pi) <= 1)}
> #declare FWave2 = function {sum (k_wave, 0.3, 3, abs ( (sqrt(x*x+y*y) - sqrt
> (9.81*k_wave*3)*T_wave)*k_wave*3) <= 0.3)}
> #declare Formula201 = function {(FWave1 (x, y, z) + FWave2 (x, y, z))/2}
>
> plane {z, 0 pigment {function {Formula201 (x,y,z)} } }
>
> Add 2 different color maps for light and dark wood, and it should look a lot
> better.


I see this idea describing...
"when annual ring pattern is not very clear"

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

> I see this idea describing...
> "when annual ring pattern is not very clear"

I just posted it to show that there are a lot of functions out there, and we can
mix and match them to eventually get the final result that we're looking for.

Whereas some base patterns may be well suited to modification and perturbation
in certain ways, others may not be.

So I think that at the present, in the absence of anything concrete, it's good
to compile a list of options, and then see what the strengths and weaknesses of
them are, and proceed from there.

And at some future point, someone may find it useful for some thing that's - not
wood.

- BE

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"Bald Eagle" <cre### [at] netscapenet> wrote:
> "And" <49341109@ntnu.edu.tw> wrote:
>
> > I see this idea describing...
> > "when annual ring pattern is not very clear"
>
> I just posted it to show that there are a lot of functions out there, and we can
> mix and match them to eventually get the final result that we're looking for.
>
> Whereas some base patterns may be well suited to modification and perturbation
> in certain ways, others may not be.
>
> So I think that at the present, in the absence of anything concrete, it's good
> to compile a list of options, and then see what the strengths and weaknesses of
> them are, and proceed from there.
>
> And at some future point, someone may find it useful for some thing that's - not
> wood.
>
> - BE

Well.

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