I've got a data field like this:

x   y   z   value
0   0   1    .232
0   0   2    .233
...

Is it possible to cut an isosurface? For example to show
a specific value of electron density etc. A tranformation
of the data to a suitable input would be simple.

Do I have to calculate a mesh first?

Thank you!

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On Wed, 10 Jul 2002 01:26:19 +0100, Plum C <bai### [at] cpfsmpgde>
wrote:

>Is it possible to cut an isosurface? For example to show
>a specific value of electron density etc. A tranformation
>of the data to a suitable input would be simple.

Look up 'threshold' in the manual and see if it helps. If it does not,
come back and hit me with something heavy for playing the wiseass.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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In article <3D2### [at] cpfsmpgde>,
 Plum C <bai### [at] cpfsmpgde> wrote:

> I've got a data field like this:
> 
> x   y   z   value
> 0   0   1    .232
> 0   0   2    .233
> ...
> 
> Is it possible to cut an isosurface? For example to show
> a specific value of electron density etc. A tranformation
> of the data to a suitable input would be simple.

It isn't clear what you are asking...do you want to generate a height 
field from a set of data giving function values at points in space? What 
do you mean by "cut an isosurface"?

You can "cut" an isosurface the same way as with most other objects, 
using CSG difference or intersection objects. You can then use the 
isosurface function as a pattern in the isosurface's texture, to show 
the function values through the cut surface, basically a cross-section. 
I'm not sure this is what you meant though.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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Dear Peter and Christopher,

thank you very much for your help. I try to clear up the misunderstanding:

I've calculated a data field with a scientific program. For
each point (x,y,z) in space I've got a value, for example
a temperature.

What I want is a plot with all points of the same value,
which built up an isosurface. I didn't mean the function
"isosurface" of povray, because I don't have an algebr.
function, but experimental respectively otherwise calculated
data points.


Example:
========

http://www.cpfs.mpg.de/departments/projects/cbv/index.html
(The small picture)


Today I've found a solution of Mr. Suzuki, who wrote his own
library file:

-------------------------------------------------------
   equpotsurface
   {
      box <1, 1, 1> <9.0, 9.0, 9.0>
      eval
      library   "ep_dat3d","test1.dat", <10,10,10,0>
      function       "data_3D_3", <1.0> // 3rd order intp.
//     function  "data_3D_1",<1.>   // 1st order intp.
//     max_gradient 1.4
      threshold -0.3
      ...
    }
-------------------------------------------------------

So I could use the povray-version together with the extensions
of Mr. Suzuki - or one of you knows a solution with povray 3.5...


Again: Thank you very much!

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Plum C wrote:
> 
> I've calculated a data field with a scientific program. For
> each point (x,y,z) in space I've got a value, for example
> a temperature.
> 
> What I want is a plot with all points of the same value,
> which built up an isosurface. I didn't mean the function
> "isosurface" of povray, because I don't have an algebr.
> function, but experimental respectively otherwise calculated
> data points.
> 
> [...]

You are not bound to mathematical functions with isosurface objects, see:

http://www.povray.org/documentation/view/195/#s06_07_11_11

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 30 Jun. 2002 _____./\/^>_*_<^\/\.______

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In article <3D2### [at] cpfsmpgde>,
 Plum C <bai### [at] cpfsmpgde> wrote:

> What I want is a plot with all points of the same value,
> which built up an isosurface. I didn't mean the function
> "isosurface" of povray, because I don't have an algebr.
> function, but experimental respectively otherwise calculated
> data points.

You don't need an algebraic function, you can use patterns as functions, 
and there is a density_file pattern. If you can translate your data to 
the .df3 file format (which is described in the documentation), you can 
put it in a pattern function and use it in an isosurface object.

The image on that page you gave would be generated using an isosurface 
and some kind of square (a very thin box, two triangles, a polygon, a 
clipped plane...whatever) with the same function used as a pattern for 
the texture.


> So I could use the povray-version together with the extensions
> of Mr. Suzuki - or one of you knows a solution with povray 3.5...

That "equpotsurface" is just a very (VERY!) old version of the 
isosurface patch. It is quite obsolete.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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