Many thanks for your interests, everyone. Sorry, am pretty busy these days.

I uploaded an image to povray.binaries.images,
http://news.povray.org/povray.binaries.images/thread/%3Cweb.45ac7028a8a7f8c81524ae1d0%40news.povray.org%3E/.

the image was rendered by using the isosurface object just like Thorsten
described.

to Vincent:
Am not sure how does povray implement the feature of "isosurface", if it
really does as what you said, that is exactly what I need. I was told that
this is also a kind of volume raytracing technique by a friend, but am not
sure. However, from the figure I uploaded, we can see patches, so I guess
that maybe povray firstly extracts the implicit surface geometry with some
tessellation technique. But this is just a guess. Another possibility is
that indeed it does with the method you said, but the normal for each
intersection is computed not so good by povray, so that the surface looks
not so smooth and appears like patches.

to Warp:
Sorry for my unclear description. According to my current limited knowledge,
the scattering, emission and absorption media are the typical feature of
volume raytracing technique, but do you think the method described by
Vincent is also a kind volume raytracing technique?

to Ingo:
Thanks for your image. I guess the white islands on the frog's skin are the
results of isosurface, am I right? :). But the image's resolution is not
large enough to determine whether there are quad patches or not.

to Thorsten:
Can you give me some comments towards the patches in my image? In fact, I
want to get a smooth surface from the volume data set. Maybe I used the
isosurface object incorrectly. the code for the isosurface object is:

#declare dens=function{pattern {density_file df3 densityfile interpolate 1}}
#declare interface=object{
  isosurface{
    function{dens(x,y,z)}
    threshold iso_value
    contained_by { box { 0.03, 0.97 } }
    open
  }
  pigment{rgbt <1., 1., 0.1, 0.5>}
  finish{
    ambient  0.3
    diffuse  0.3
    roughness 0.5
    brilliance 1
  }
  scale 1.06
  translate -0.03
}

The resolution for the volume data I used is 32x32x32, but i think finer
data can only alleviate the problem to some degree. Yet, I should try finer
data...

Post a reply to this message