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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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On Wed, 10 Sep 2003 18:28:53 +0200, "Sebastian H." <van### [at] gmxde> wrote:
> Has anyone written a programm that does this for isosurfaces written in
> povray syntax?
you mean isosurface written in povray syntax ot program written in povray
syntax ? Is that what you are looking for
http://news.povray.org/search/?s=approximation ?
ABX
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In article <3f5e3bb5@news.povray.org>, Warp <war### [at] tagpovrayorg>
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.
But POV isosurface functions are not necessarily derivable, or even
contiguous.
--
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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Christopher James Huff <cja### [at] earthlinknet> wrote:
> But POV isosurface functions are not necessarily derivable, or even
> contiguous.
Most are.
And besides, I faintly remember that the marching triangles algorithm
should work quite well with sharp edges as well.
--
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -
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