POV-Ray : Newsgroups : povray.general : MRFractal question Server Time
18 Nov 2024 05:11:07 EST (-0500)
  MRFractal question (Message 1 to 8 of 8)  
From: Tom Melly
Subject: MRFractal question
Date: 11 Oct 2002 04:54:47
Message: <3da691d7$1@news.povray.org>
Up until recently, I'd always got my multi-ridge code "wrong", in that I had
passed (x,y,z) to it, not (x,0,z).

The thing is, this never seemed to cause any noticable problems, discontinuous
floating bits, etc. I don't even recall seeing such artifacts when tweaking
params - how come?



--
#macro A(V,B,C,R)#while(B-256)#if(V-128/B>=0)sphere{0,.5translate<C-4R-1,9>
pigment{rgb<1-C/8R/2C/8>}}#local V=V-128/B;#end#local B=B*2;#local C=C+1;#
end#end A(234,1,0,2)A(85,1,0,1)A(81,1,0,0)light_source{-5 1}//Tom Melly


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From: Christopher James Huff
Subject: Re: MRFractal question
Date: 11 Oct 2002 13:00:56
Message: <chrishuff-265C14.12573711102002@netplex.aussie.org>
In article <3da691d7$1@news.povray.org>,
 "Tom Melly" <tom### [at] tomandlucouk> wrote:

> The thing is, this never seemed to cause any noticable problems, discontinuous
> floating bits, etc. I don't even recall seeing such artifacts when tweaking
> params - how come?

It isn't really wrong, just sometimes causes problems that are hard to 
avoid. Setting y to a constant value makes it impossible to have 
overhangs or perfectly vertical surfaces, which you might want. Setting 
it to y makes "floaters" possible, not inevitable.

-- 
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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From: Rick [Kitty5]
Subject: Re: MRFractal question
Date: 12 Oct 2002 05:36:06
Message: <3da7ed06$2@news.povray.org>
Christopher James Huff wrote:
> Setting it to y makes "floaters" possible, not inevitable.

And we all know how embarrassing they can be....
--
Rick

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From: Christopher James Huff
Subject: Re: MRFractal question
Date: 13 Oct 2002 12:52:16
Message: <chrishuff-07C01C.12471413102002@netplex.aussie.org>
In article <3da7ed06$2@news.povray.org>,
 "Rick [Kitty5]" <ric### [at] kitty5com> wrote:

> And we all know how embarrassing they can be....

Embarassing? Huh?
Annoying, yes...but even if you don't notice them in a landscape and 
someone else does, I don't understand why it would be very embarassing.

-- 
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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From: Johannes Dahlstrom
Subject: Re: MRFractal question
Date: 13 Oct 2002 15:07:26
Message: <3da9c46d@news.povray.org>
Christopher James Huff wrote:
> It isn't really wrong, just sometimes causes problems that are hard to
> avoid. Setting y to a constant value makes it impossible to have
> overhangs or perfectly vertical surfaces, which you might want. Setting
> it to y makes "floaters" possible, not inevitable.

Yep. IMHO giving y a non-constant value results usually in much more
realistic-looking landscape. Multiplying y with a small enough constant
gets rid of most, if not all, floaters, while keeping the overhangs and 
staying overall "not-height_fieldy" ;). Something like <x,y/4,z> should 
work fine.


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From: Christopher James Huff
Subject: Re: MRFractal question
Date: 14 Oct 2002 17:12:30
Message: <chrishuff-DEC1C3.17073314102002@netplex.aussie.org>
In article <3da9c46d@news.povray.org>,
 Johannes Dahlstrom <sad### [at] tkukoulufi> wrote:

> Yep. IMHO giving y a non-constant value results usually in much more
> realistic-looking landscape.

Unless you are doing a sheer cliff. ;-)


> Multiplying y with a small enough constant gets rid of most, if not 
> all, floaters, while keeping the overhangs and staying overall 
> "not-height_fieldy" ;). Something like <x,y/4,z> should work fine.

Raising the vertical gradient would work similarly..."y*4 + noise()" 
should be pretty close to "y + noise()/4".

-- 
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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From: Marc-Hendrik Bremer
Subject: Re: MRFractal question
Date: 15 Oct 2002 04:17:49
Message: <3dabcf2d@news.povray.org>
"Christopher James Huff" <chr### [at] maccom> schrieb im Newsbeitrag
news:chr### [at] netplexaussieorg...

> > Multiplying y with a small enough constant gets rid of most, if not
> > all, floaters, while keeping the overhangs and staying overall
> > "not-height_fieldy" ;). Something like <x,y/4,z> should work fine.
>
> Raising the vertical gradient would work similarly..."y*4 + noise()"
> should be pretty close to "y + noise()/4".

I don't think so. In the first case, your surface will be displaced by a
full unit, (but it will reach the threshold at another position. In the
second version, the plane will be displaced by only 1/4 of a unit.
Is this wrong?

Marc-Hendrik


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From: Christopher James Huff
Subject: Re: MRFractal question
Date: 16 Oct 2002 12:26:36
Message: <chrishuff-96E7AB.12214716102002@netplex.aussie.org>
In article <3dabcf2d@news.povray.org>,
 "Marc-Hendrik Bremer" <Mar### [at] t-onlinede> wrote:

> I don't think so. In the first case, your surface will be displaced by a
> full unit, (but it will reach the threshold at another position. In the
> second version, the plane will be displaced by only 1/4 of a unit.
> Is this wrong?

Uh, I don't know what I was thinking...blame it on a cold I had.
Sorry.

-- 
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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