POV-Ray : Newsgroups : povray.general : What's this intersection jargon? Server Time
11 Aug 2024 01:15:21 EDT (-0400)
  What's this intersection jargon? (Message 1 to 5 of 5)  
From: Greg M  Johnson
Subject: What's this intersection jargon?
Date: 10 Oct 1999 11:35:39
Message: <3800b24b@news.povray.org>
How would I intersect an isosurface with a plane?
In particular, how would I take a moving, thin slice through an
isosurface??

Say I want to take a moving slice through my chewing gum galaxy surface:

 {(noise3d(x*f,y*f,z*f)+((sqrt(x^2+y^2+z^2)/R)^1))}

I tried intersecting it with the following two planes, but either
superpatch isn't responding, or I don't understand the math.
I tried

&(z+zha)&(-z+.002+zha)

with a variable zha. It doesn't work at all except zha=0.
I tried to guess how to intersect the inverse of a plane, but various
guesses with a ! symbol only generated errors...


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From: Buckaroo Bill
Subject: Re: What's this intersection jargon?
Date: 10 Oct 1999 11:38:30
Message: <3800b2f6@news.povray.org>
Greg M. Johnson wrote:
>
> I tried intersecting it with the following two planes, but either
> superpatch isn't responding, or I don't understand the math.
> I tried
>
> &(z+zha)&(-z+.002+zha)
>

    Me too. I tried all sorts of things until late last ni... early this
morning. I couldn't get any sort of a slice.


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From: Chris Huff
Subject: Re: What's this intersection jargon?
Date: 10 Oct 1999 13:09:33
Message: <3800C8C5.A3E8A0B8@compuserve.com>
This worked for me:  &(x - sliceThickness/2 + sliceOffset)&(-x -
sliceThickness/2 - sliceOffset)


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From: Greg M  Johnson
Subject: thanks.
Date: 10 Oct 1999 15:00:09
Message: <3800e239@news.povray.org>
THANKS.
Perhaps the problem was with the offset in my equation.
Also, I realized I could have used good ol' CSG, too......

Chris Huff wrote:

> This worked for me:  &(x - sliceThickness/2 + sliceOffset)&(-x -
> sliceThickness/2 - sliceOffset)


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From: Buckaroo Bill
Subject: Re: What's this intersection jargon?
Date: 10 Oct 1999 17:20:01
Message: <38010301@news.povray.org>
/// I ended up doing this

#declare Frequency      = 9.0;
#declare Dispersion     = 2.0;
#declare Slice          = 0.1;       /// the actual thickness
#declare Radius         = 1.0;    /// is Slice/Radius

isosurface {
         function
          { (noise3d(x*Frequency,y*Frequency,z*Frequency))
           +((sqrt(x^2+y^2+z^2)/Radius)^Dispersion)
           &abs(z/Slice)
          }
               accuracy 0.01
               threshold 1.0
               sign 1
               bounded_by {
               sphere{0, 1}
               }
        pigment{rgb 1}
        }


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