I've been experimenting with POV's f_noise3d.
It can be used to simulate POV's turbulence in patterns but it cannot
simulate lambda because the function is 3-dimensional.
I think f_noise4d should do the trick. If you try to get the next turbulence
value from the 4th dimension instead of x,y or z. Lambda is the distance
travelled along the t-axel on each octave (Is it not?).

f_noise4d(x,y,z,t) could also be used in animating 3d-clouds. If you take
the next value from x,y or z the clouds seem to be moving instead of
changing. And if you want the clouds to move along x and change just move
the function along the vector<1,0,0,1>.
Would f_noise5d be needed if you want clouds with lambda?

Do we need a patch to add f_noise4d to POV or does anybody know how to do
4d-interpolation? (the f_noise3d uses 3d-interpolation, right?).

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On Sun, 13 Oct 2002 03:23:25 EDT, "Pyry" <fro### [at] suomi24fi> wrote:

>Do we need a patch to add f_noise4d to POV or does anybody know how to do
>4d-interpolation? (the f_noise3d uses 3d-interpolation, right?).

IIRC Slime is working on a 4D noise patch - check out recent posts in
povray.binaries.animations for examples.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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In article <web.3da91f6d351cc2ee398d8dbb0@news.povray.org>,
 "Pyry" <fro### [at] suomi24fi> wrote:

> I've been experimenting with POV's f_noise3d.
> It can be used to simulate POV's turbulence in patterns but it cannot
> simulate lambda because the function is 3-dimensional.
> I think f_noise4d should do the trick. If you try to get the next turbulence
> value from the 4th dimension instead of x,y or z. Lambda is the distance
> travelled along the t-axel on each octave (Is it not?).
> 
> f_noise4d(x,y,z,t) could also be used in animating 3d-clouds. If you take
> the next value from x,y or z the clouds seem to be moving instead of
> changing. And if you want the clouds to move along x and change just move
> the function along the vector<1,0,0,1>.
> Would f_noise5d be needed if you want clouds with lambda?
> 
> Do we need a patch to add f_noise4d to POV or does anybody know how to do
> 4d-interpolation? (the f_noise3d uses 3d-interpolation, right?).

4D noise would be useful, but not for this. You misunderstood the way 
lambda works, it affects the scaling of the amplitude of each octave of 
noise. No additional dimensions necessary.

Octaves: number of noise samples taken.
Omega: the size scaling applied to the size scaling factor for each 
sample.
Lambda: the amplitude scaling applied to the amplitude scaling factor 
for each sample.

Pseudo-code for a turbulence function:

vector total = < 0, 0, 0>;
vector pt = point;
float lm = 1;
for(int n = 0; n < octaves; n++)
{
    total += vnoise(pt)*lm;
    pt *= omega;
    lm *= lambda;
}

The main thing you need is a vector noise function...POV has one that it 
uses for turbulence, but it hasn't been made available to functions for 
the simple reason that functions can't handle vectors.
And besides, if you just want different noise functions, separate noise 
generators with different seeds would be better...4D noise is more 
expensive to compute than 3D noise.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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Christopher James Huff wrote:
>And besides, if you just want different noise functions, separate noise
>generators with different seeds would be better...4D noise is more
>expensive to compute than 3D noise.
>

How do I change the seed of f_noise3d in POV?

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In article <web.3dab04b580de19a8398d8dbb0@news.povray.org>,
 "Pyry" <fro### [at] suomi24fi> wrote:

> How do I change the seed of f_noise3d in POV?

The same way you use 4D noise.
(meaning: you don't, someone has to write a patch for it)

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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>The same way you use 4D noise.
>(meaning: you don't, someone has to write a patch for it)

Here's a thought, could it be possible to create two different sets of 2d
noise, then use the 2 dimensions of one set for the x and y changes, and
the 2 from the other set for the z and t changes?

Rohan _e_ii

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In article <web.3db3690a80de19a8d02c7b870@news.povray.org>,
 "Rohan Bernett" <rox### [at] yahoocom> wrote:

> Here's a thought, could it be possible to create two different sets of 2d
> noise, then use the 2 dimensions of one set for the x and y changes, and
> the 2 from the other set for the z and t changes?

Won't work, unless you want some kind of wierd 2D vector noise. It gives 
you 2 float values, what do you do with them? Average? Multiply? Neither 
gives quite the right result, and at the end, changing one coordinate 
won't change the results in the same way...half of the source of the 
pattern will remain constant.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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>> Here's a thought, could it be possible to create two different sets of 2d
>> noise, then use the 2 dimensions of one set for the x and y changes, and
>> the 2 from the other set for the z and t changes?

Perhaps I should have written it like this:

p1=pattern1
p2=pattern2
f=final

p1.x = f.x
p1.y = f.y
p2.x = f.z
p2.y = f.t

Using the coordinates of one set of noise for the x and y coordinates, and
the x and y from the other for the z and t. Then use the values at those
coordinates. Would this work?

Rohan _e_ii

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In article <web.3db4bdb480de19a818ccf4f70@news.povray.org>,
 "Rohan Bernett" <rox### [at] yahoocom> wrote:

> Using the coordinates of one set of noise for the x and y coordinates, and
> the x and y from the other for the z and t. Then use the values at those
> coordinates. Would this work?

No, and for the same reason, all you did was swap things around. As you 
change one component, the effect will be that the result will have 
static features blended with moving features. True 4D noise is something 
completely different, and needs a patch to be useful.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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