Wasn't it Thorsten Froehlich who wrote:
>In article <C5f### [at] econymdemoncouk> , Mike Williams 
><mik### [at] nospamplease>  wrote:
>
>> I confirm the numbers, but I don't think it's anything to do with the
>> nesting of selects.
>>
>> If you change to noise generator 1, the numbers come out even. It looks
>> to me like there's a subtlety in noise type 3 that causes
>> f_noise3d(integer, integer, 0) to always be greater than 1/3. I really
>> don't see that as being a problem because you shouldn't really expect
>> noise3d to be a random number generator.
>
>Thank you for finding this!  So it is not a bug, but simply the wrong
>noise_generator.  There has a lot been written about the old/default noise
>generator's problems, and I guess this is one good example of them.

It's the NEW noise generator that is exhibiting the strange behaviour at
integer coordinates. The old noise generator that behaves sensibly in
this respect.

2.6.1: The default generator, type 3, is a completely new Perlin noise
function. You can also choose noise_generator 1, which behaves like the
noise in POV-Ray 3.1 and earlier.

-- 
Mike Williams
Gentleman of Leisure

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On Mon, 1 Oct 2001 12:28:02 -0400, "Slime" <noo### [at] hotmailcom>
wrote:

> Well, for them to appear *evenly*, you would have to change the (1/2) to
> (2/3).

I think you are wrong.

ABX

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On Mon, 1 Oct 2001 19:18:42 +0100, Mike Williams <mik### [at] nospamplease>
wrote:

> Wasn't it W?odzimierz ABX Skiba who wrote:
> > in my opionion it should evenly return 0, 1 and 2
> >
> > 0 - 0 times
> > 1 - 64161 times
> > 2 - 35839 times
>
> I confirm the numbers, but I don't think it's anything to do with the
> nesting of selects.
>
> If you change to noise generator 1, the numbers come out even. It looks
> to me like there's a subtlety in noise type 3 that causes
> f_noise3d(integer, integer, 0) to always be greater than 1/3.

Thanks for finding and pointing this.
I think there should be note withing documentation about
characteristic of noise generators.

> I really
> don't see that as being a problem because you shouldn't really expect
> noise3d to be a random number generator.

I don't expect. They are just good to make "random but constant"
mosaics in textures/pigments. :-)

> If you do the same thing, with the default noise generator, but without
> the "floor()"s, then the results are:-
>
> 0 - 13007 times
> 1 - 45476 times
> 2 - 41517 times

they are similiar to noise_generator 2 with floor() for args

> By the way, since you seem to like using "Interpolate()",

sorry. it's macro from standard "math.inc"

ABX

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Skiba wrote:

> I think there should be note withing documentation about
> characteristic of noise generators.
> 

What kind of characteristics do you mean and what are they.
I posted two images in p.b-t.b with histograms, is this sufficient?

Ingo

-- 
Photography: http://members.home.nl/ingoogni/
Pov-Ray    : http://members.home.nl/seed7/

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On 22 Oct 2001 08:37:06 -0400, ingo <ing### [at] homenl> wrote:
> in news:s9p7ttk0cqadgpvrkjquu9r2c5tai77u6g@4ax.com W?odzimierz ABX 
> Skiba wrote:
>
> > I think there should be note withing documentation about
> > characteristic of noise generators.
> > 
>
> What kind of characteristics do you mean and what are they.

I'm talking about few words about results for some special args. As
this thread shows one sentence can be: "for integer args generator 3
returns only values above 1/3." Without sources I can't give more
examples - I found only this by experience. Perhaps something like
this occure for some generators:
noise(x,0,0)=noise(0,x,0)=noise(0,0,x). Or : noise(x,y,0)=noise(y,x,0)

> I posted two images in p.b-t.b with histograms, is this sufficient?

I though about characteristic as description. Such images have sense
only in small range. And are usfull when such range is repeated over
and over. But perhaps your images could be usefull for others.

ABX

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Unfortunately, Outlook Express seems to delete old messages and I can't
figure out how to make it *stop* doing that, so I don't really remember the
original post that this applied to. However, if I remember correctly, I
think it was a matter of splitting it up into thirds, and what was being
done was someone was testing if a number between zero and one was less than
1/3, and then if it was less than 1/2. I figured it should be 1/3 and then
2/3, to split it up evenly. But I don't really remember or care enough to
argue the point anymore. =)

- Slime
[ http://www.slimeland.com/ ]
[ http://www.slimeland.com/images/ ]


news:0mq7tt888pac9hsj5r5b4l4jatn5ooahi5@4ax.com...
> On Mon, 1 Oct 2001 12:28:02 -0400, "Slime" <noo### [at] hotmailcom>
> wrote:
>
> > Well, for them to appear *evenly*, you would have to change the (1/2) to
> > (2/3).
>
> I think you are wrong.
>
> ABX

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>On Mon, 1 Oct 2001 19:18:42 +0100, Mike Williams <mik### [at] nospamplease>
>wrote:
>
>> By the way, since you seem to like using "Interpolate()", I guess 
>> that you have some idea of what it's supposed to do and what the 
>> parameters mean. Would it be possible for you to enlighten the rest 
>> of us? The docs have a bit of a hole there.
>
>sorry. it's macro from standard "math.inc"

I knew that, but the documentation says

"Interpolate(GC, GS, GE, TS, TE, Method). Interpolation macro...can
someone explain this one?"

The comments in math.inc aren't helpful either, but you seemed to be
using it as if you had some idea what the parameters were for. The rest
of us are rather in the dark.

-- 
Mike Williams
Gentleman of Leisure

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"Slime" <noo### [at] hotmailcom> wrote in message
news:3bd445e2$1@news.povray.org...
> Unfortunately, Outlook Express seems to delete old messages and I can't
> figure out how to make it *stop* doing that, so I don't really remember
the
> original post that this applied to.

Have a look in povray.announce.frequently-asked-questions. The most recent
post there is about Outlook express settings.

Gail
--
*************************************************************************
* gsh### [at] monotixcoza                *   Step into the abyss,           *
* http://www.rucus.ru.ac.za/~gail/   *   and let go.          Babylon 5 *
*************************************************************************
* Just think of me as the storm before the calm     Magic: The Gathering*
*************************************************************************

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On Mon, 22 Oct 2001 18:35:59 +0100, Mike Williams <mik### [at] nospamplease>
wrote:

> Wasn't it W?odzimierz ABX Skiba who wrote:
> > sorry. it's macro from standard "math.inc"
>
> I knew that, but the documentation says
>
> "Interpolate(GC, GS, GE, TS, TE, Method). Interpolation macro...can
> someone explain this one?"
>
> The comments in math.inc aren't helpful either, but you seemed to be
> using it as if you had some idea what the parameters were for. The rest
> of us are rather in the dark.

Well, I missed note from doc and get it only with content of include
file. It looks very simple to me and I can explain a little. This
macro gets value (first arg) from range <global_start,global_end>.
Than it makes calculations to put it into another range
<target_start,target_end>. The way how it calculate depends on last
argument called Method. For Method=0 characteristic of calculation
looks like part of sinusoid. For Method=1 it simple linear
calculation. For Method>0 it goes with exponent.

Sample of use: Looking for smooth movement from one point to another
for animations you need only one line.
Result=Interpolate(clock,initial_clock,final_clock,StartPoint,EndPoint,0)

I suppose it is designed as macro (I think slower) becouse function
forbids use it with vectors and colors for target range.

To show characteristic of interpolations I made sample file I'll post
after moment to p.b-t.binaries. Feel free to use its output within doc
or as sample file or merge it with math.pov from incdemo.

ABX

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On Mon, 22 Oct 2001 12:12:43 -0400, "Slime" <noo### [at] hotmailcom>
wrote:

> Unfortunately, Outlook Express seems to delete old messages and I can't
> figure out how to make it *stop* doing that, so I don't really remember the
> original post that this applied to.

http://news.povray.org/povray.beta-test/18823/

> However, if I remember correctly, I
> think it was a matter of splitting it up into thirds, and what was being
> done was someone was testing if a number between zero and one was less than
> 1/3, and then if it was less than 1/2. I figured it should be 1/3 and then
> 2/3, to split it up evenly. But I don't really remember or care enough to
> argue the point anymore. =)

But I can't stay when you are wrong. My english is not enough to
explain but take this script for proof. It takes _two_ random values
just like original script. I don't know how to set up "follow-up" in
my newsreader but change group if you want talk about this problem.

#include "stdinc.inc"
#local test=function(A,B){select(A-(1/3),0,select(B-(1/2),1,2))}
#local Count=array[3]{0,0,0};
#local Seed=0;
#local Counter=0;
#while(Counter<10000)
  #local Result=test(rand(Seed),rand(Seed));
  #local Count[Result]=Count[Result]+1;
  #local Counter=Counter+1;
#end
#warning Str(Count[0])
#warning Str(Count[1])
#warning Str(Count[2])

ABX

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