I've been looking around and couldn't find any tool to 'convert' an 
isosurface to a mesh. Does anyone have this kind of tool (preferably 
povray script) handy ? Otherwise I'll have to write it myself, but I 
suspect it will take some time, so if I can avoid it ...  :-)

Tx,

JC

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On Tue, 09 Sep 2003 19:44:08 +0200, "JC (Exether)" <no### [at] spamfr> wrote:
> I've been looking around and couldn't find any tool to 'convert' an 
> isosurface to a mesh. Does anyone have this kind of tool (preferably 
> povray script) handy ? Otherwise I'll have to write it myself, but I 
> suspect it will take some time, so if I can avoid it ...  :-)

http://news.povray.org/search/?s=tessel

Perhaps some of http://members.home.nl/seedseven/#MMMM could be useful too.

ABX

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"JC (Exether)" <no### [at] spamfr> wrote in news:3f5e1162$1@news.povray.org:

> I've been looking around and couldn't find any tool to 'convert' an 
> isosurface to a mesh. Does anyone have this kind of tool (preferably 
> povray script) handy ? Otherwise I'll have to write it myself, but I 
> suspect it will take some time, so if I can avoid it ...  :-)

The difficulty with isosurfaces is that they are functions and don't 
necessarily present an actual contiguous surface.  A tessellation routine 
that can handle any isosurface function would be very difficult, next to 
impossible.

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JC (Exether) wrote:
> I've been looking around and couldn't find any tool to 'convert' an 
> isosurface to a mesh. Does anyone have this kind of tool (preferably 
> povray script) handy ? Otherwise I'll have to write it myself, but I 
> suspect it will take some time, so if I can avoid it ...  :-)

There is the tesselation patch:

http://jgrimbert.free.fr/pov/patch/tessel/index.html

which also works for isosurfaces and there were various macros for this 
posted over the time.

None the less you will find that all these methods are slow (esp. as 
script) and don't really convert the isosurface - they just create a 
rough approximation.

-- Christoph

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None <Non### [at] onca> wrote:
> The difficulty with isosurfaces is that they are functions and don't 
> necessarily present an actual contiguous surface.  A tessellation routine 
> that can handle any isosurface function would be very difficult, next to 
> impossible.

  Actually tesselating a contiguous and derivable (read: smooth) isosurface
(which most are) is perfectly possible and not even too difficult. An
algorithm like the marching triangles is perfectly suitable.

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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Wasn't it JC (Exether) who wrote:
>I've been looking around and couldn't find any tool to 'convert' an 
>isosurface to a mesh. Does anyone have this kind of tool (preferably 
>povray script) handy ? Otherwise I'll have to write it myself, but I 
>suspect it will take some time, so if I can avoid it ...  :-)

I've looked at Kevin Loney's approximation macro and Jaap Frank's go-
faster version for my Isosurface tutorial. Note that for many
isosurfaces it is faster to render the isosurface than it is to use the
approximation.

For parametric isosurfaces, there's Ingo Janssen's param.inc, which has
the advantage of being considerably faster than the original isosurface.

See my <http://www.econym.demon.co.uk/isotut/> for details.

-- 
Mike Williams

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Thanks all for you input, I will experiment that.
All I want to do is to have a basic equivalent to a very time-consuming 
isosurface I have and use the iso for the real render.

JC

JC (Exether) wrote:
> I've been looking around and couldn't find any tool to 'convert' an 
> isosurface to a mesh. Does anyone have this kind of tool (preferably 
> povray script) handy ? Otherwise I'll have to write it myself, but I 
> suspect it will take some time, so if I can avoid it ...  :-)
> 
> Tx,
> 
> JC
>

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Warp <war### [at] tagpovrayorg> wrote in news:3f5e3bb5@news.povray.org:

> None <Non### [at] onca> wrote:
>> The difficulty with isosurfaces is that they are functions and don't 
>> necessarily present an actual contiguous surface.  A tessellation
>> routine that can handle any isosurface function would be very
>> difficult, next to impossible.
> 
>   Actually tesselating a contiguous and derivable (read: smooth)
>   isosurface 
> (which most are) is perfectly possible and not even too difficult. An
> algorithm like the marching triangles is perfectly suitable.

I perfectly realize that, which is why I was reffering to non contiguous 
surfaces and "any" (read: all) function.

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> I've looked at Kevin Loney's approximation macro...
> Note that for many isosurfaces it is faster to render
> the isosurface than it is to use the approximation.

Considering the time to postprocess the data from Kevin Loney's macro,
perhaps it's faster to run an isosurface render. But I've found his macro to
be really useful. But you need to save the data. Possibly (as I did) in .OBJ
file format and run it through triangle decimation algoritm (that's always
neat). Then export back to mesh2 and the result will surely render faster
than any isosurface. It will, however, still use at least 10 times more
memory of course.

Regards,
Hugo

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Warp wrote:
> None <Non### [at] onca> wrote:
> 
>>The difficulty with isosurfaces is that they are functions and don't 
>>necessarily present an actual contiguous surface.  A tessellation routine 
>>that can handle any isosurface function would be very difficult, next to 
>>impossible.
> 
> 
>   Actually tesselating a contiguous and derivable (read: smooth) isosurface
> (which most are) is perfectly possible and not even too difficult. An
> algorithm like the marching triangles is perfectly suitable.
> 

Has anyone written a programm that does this for isosurfaces written in 
povray syntax?

Sebastian H.

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