POV-Ray : Newsgroups : povray.general : Iso Implementation Server Time
7 Aug 2024 01:17:42 EDT (-0400)
  Iso Implementation (Message 1 to 4 of 4)  
From: Ben Chambers
Subject: Iso Implementation
Date: 10 Jan 2002 17:52:53
Message: <3c3e1b45@news.povray.org>
Does the isosurface implementation work by:

a)  Subdividing a ray, testing for inside / outside, until a good
approximation of the border is found,

b) Symbolically solving the function for the intersection with the ray?

If (a) is used, would (b) provide better speed?  Or would the math be "not
trivial" (as my friend always says)?

...Chambers


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From: Slime
Subject: Re: Iso Implementation
Date: 10 Jan 2002 18:00:06
Message: <3c3e1cf6$1@news.povray.org>
> Does the isosurface implementation work by:
>
> a)  Subdividing a ray, testing for inside / outside, until a good
> approximation of the border is found,
>
> b) Symbolically solving the function for the intersection with the ray?

I suspect A, and I think that the procedure is repeated until the distance
between two sampled points is less than or equal to the value specified for
accuracy.

I know it's not B, because that would be analytically impossible in many,
many situations, especially those involving pigments and POV-Ray generated
patterns.

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


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From: Thorsten Froehlich
Subject: Re: Iso Implementation
Date: 10 Jan 2002 20:24:40
Message: <3c3e3ed8@news.povray.org>
In article <3c3e1b45@news.povray.org> , "Ben Chambers" 
<bdc### [at] yahoocom> wrote:

> Or would the math be "not
> trivial" (as my friend always says)?

Lets just say impossible, because that pretty much is straight to the point.

    Thorsten

____________________________________________________
Thorsten Froehlich
e-mail: mac### [at] povrayorg

I am a member of the POV-Ray Team.
Visit POV-Ray on the web: http://mac.povray.org


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From:
Subject: Re: Iso Implementation
Date: 11 Jan 2002 02:21:24
Message: <q54t3ukah7489tmfiomlta5022j3rvg55o@4ax.com>
On Thu, 10 Jan 2002 14:58:17 -0800, "Ben Chambers" <bdc### [at] yahoocom>
wrote:

> Does the isosurface implementation work by:
> a)  Subdividing a ray, testing for inside / outside, until a good
> approximation of the border is found,

probably something like this
process seems much more complicated and depends on isosurface parameters

> b) Symbolically solving the function for the intersection with the ray?

don't even think about it

> If (a) is used, would (b) provide better speed?  Or would the math be "not
> trivial" (as my friend always says)?

documentation says: "In contrast to the other mathematically based shapes in
POV-Ray, isosurfaces are approximated during rendering and therefore they are
sometimes more difficult to handle."

more you can read at http://www.povray.org/working-docs/id000167.html

ABX


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