"Anton Sherwood" <bro### [at] poboxcom> wrote...
> Nathan Kopp wrote:
> > The mapping is (if I did the math correctly):
> > old_value = (new_value / 0.48985582) - 1.05242 + 0.5
>
> what is the significance of these numbers?

They are a result of some tests that Xander did on the "old" noise3d
function.  The function itself has more flaws (such as a grid pattern that
you can see if you look closely).

Actually, 0.5 should probably have been used instead of 0.48985582 and 1.0
should probably have been used instead of 1.05242.  I don't know enough
about the original function to know details, though.  The issue is that the
range of the original function was incorrect.

-Nathan

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"Chris Huff" <chr### [at] maccom> wrote...
> The affected patterns include:
  ...
> crackle(with "solid" on, at least)

Only crackle solid is affected.  The old-style crackle does not use noise.

> And of course, the ridged multifractal functions.

Hmm... I forgot about those.

> In addition, anything
> using turbulence will be affected.

Actually, not everything.  There are two kinds of turbulence in POV.  The
first one, "Turbulence," uses the "Noise" function which is affected.  The
second one, "DTurbulence," which uses the 3D "DNoise" is not affected.  The
following patterns will use "Turbulence" if "classic" turbulence is used.
All other patterns, and all turbulence warps use DTurbulence and are
therefore not affected.

Classic turbulence affected for:
marble
spiral1
spiral2
fog

Also, iridescence uses the "Turbulence" funciton, so it is affected by the
change.

-Nathan

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In article <3996dcf0@news.povray.org>, "Nathan Kopp" <Nat### [at] Koppcom> 
wrote:

> Only crackle solid is affected.  The old-style crackle does not use 
> noise.

That is what I meant.


> Actually, not everything.  There are two kinds of turbulence in POV.  
> The first one, "Turbulence," uses the "Noise" function which is 
> affected.  The second one, "DTurbulence," which uses the 3D "DNoise" 
> is not affected.

How is DNoise() different from Noise()? This is something I have never 
figured out. I had just assumed both had the same problem.


> Classic turbulence affected for:
> marble
> spiral1
> spiral2

I thought only agate had a specialized turbulence...why do these 
patterns have a different turbulence from the others?

-- 
Christopher James Huff - Personal e-mail: chr### [at] maccom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://homepage.mac.com/chrishuff/
TAG Web page: http://tag.povray.org/

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> "Chris Huff" <chr### [at] maccom> wrote...
> > The affected patterns include:
>   ...
> > crackle(with "solid" on, at least)

Nathan Kopp wrote:
> Only crackle solid is affected.  The old-style crackle does not use noise.

What's crackle solid?  (I *did* rtfm!)

-- 
Anton Sherwood  --  br0### [at] p0b0xcom  --  http://ogre.nu/

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In article <3996F67E.1C9E657B@pobox.com>, Anton Sherwood 
<bro### [at] poboxcom> wrote:

> What's crackle solid?  (I *did* rtfm!)

It makes each "cell" of the crackle pattern a different (solid) color, 
and it is documented in the MegaPOV manual, so I suggest you rtfm again. 
Specifically, section 8.3.2 "Crackle types". :-)

-- 
Christopher James Huff - Personal e-mail: chr### [at] maccom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://homepage.mac.com/chrishuff/
TAG Web page: http://tag.povray.org/

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Chris Huff wrote:
> 
> 
> How is DNoise() different from Noise()? This is something I have never
> figured out. I had just assumed both had the same problem.
> 
As much as I understand, Noise and DNoise should be fairly same
(DNoise's first component has same value as Noise's return value for
same evaluation point), so I think that this fix should be applied there
as well.

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"Vahur Krouverk" <vah### [at] aetecee> wrote...
> Chris Huff wrote:
> >
> >
> > How is DNoise() different from Noise()? This is something I have never
> > figured out. I had just assumed both had the same problem.
> >
> As much as I understand, Noise and DNoise should be fairly same
> (DNoise's first component has same value as Noise's return value for
> same evaluation point), so I think that this fix should be applied there
> as well.

The algorithm that produces the fractal pattern for DNoise and Noise is very
similar.  DNoise produces a vector of noise, while Noise produces a single
output.

The algorithm itself basically produces an output in the range of
approximately [-1,1].  This is what DNoise wants for each component, so it
doesn't change anything.  However, Noise needs to change it to [0,1] for use
in a pattern.  However, in the official conversion, the change is incorrect,
and it over-saturates the top end.  MegaPov just fixes the conversion.

The old version simply adds 0.5, while the new version (for all practical
purposes) adds 1 and then divides by two.

-Nathan

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> > What's crackle solid?  (I *did* rtfm!)

Chris Huff wrote:
> It makes each "cell" of the crackle pattern a different (solid) color,
> and it is documented in the MegaPOV manual, so I suggest you rtfm again.

Oh: rtwfm; r2fm.

Just started playing with Mega yesterday.  When I get my obligatory
Shiny Sphere (containing an iso) the way I want it, I'll put it on a
plane crackle solid rather than checkered.

-- 
Anton Sherwood  --  br0### [at] p0b0xcom  --  http://ogre.nu/

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Nathan Kopp wrote:
> 
> 
> The algorithm that produces the fractal pattern for DNoise and Noise is very
> similar.  DNoise produces a vector of noise, while Noise produces a single
> output.
> 
> The algorithm itself basically produces an output in the range of
> approximately [-1,1].  This is what DNoise wants for each component, so it
> doesn't change anything.  However, Noise needs to change it to [0,1] for use
> in a pattern.  However, in the official conversion, the change is incorrect,
> and it over-saturates the top end.  MegaPov just fixes the conversion.
> 

Ah, so DNoise values are supposed to be between -1 and 1? Indeed, If I
think about it, then in official version its range was not changed
either.

> The old version simply adds 0.5, while the new version (for all practical
> purposes) adds 1 and then divides by two.
By old You mean official version (3.02??) and by new 3.5?
Are those constants, found by Xander and used in MegaPOV, removed in new
version and (+1)/2 used instead?

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"Vahur Krouverk" <vah### [at] aetecee> wrote...
>
> Ah, so DNoise values are supposed to be between -1 and 1? Indeed, If I
> think about it, then in official version its range was not changed
> either.

It was changed, but not correctly.

> By old You mean official version (3.02??) and by new 3.5?

Yes.

> Are those constants, found by Xander and used in MegaPOV, removed in new
> version and (+1)/2 used instead?

Yes.  (+1) / 2 will be used.  Remember that the constants Xander found were
very close to that and were determined by sampling a thousand or so points.

-Nathan

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