i got a trianglar mesh file, and i render it with the "mesh2" object, the
result can be seen in the attachment. But there so many black holes in the
image.

in my mesh file, there are three data blocks: vertices, normals, and
triangles' vertex indices. I am sure that the vertices and the trianlges'
vertex indices are absolutely right, so i think maybe there are two
possible reasons for the unwanted black holes: 1,there are many uncorrect
normals; 2,there are many missing triangles on the mesh.

For the reason 2, i have not any idea about how to make it. and for the
reason 1, i have already reconstruct all the normals totally based on the
vertices and the triangular topology, but there are still many black holes.

so now, i think that maybe pov-ray ITSELF can get rid of(or alleviate) the
black hole problem EVEN with missing triangles. the rendering code i use is
as
follows:

object{
  TriangleObjMesh  // water surface mesh object
  material {
  texture {
    pigment {color rgbt <1, 1, 1, 0.85>}
    finish {
      ambient 0.0
      diffuse 0.0
      reflection {0.0, 1.0}
      specular 1.5
      roughness 0.003
    }
  }
  interior {ior 1.333}
}


IS there anybody can give me some advice??

Post a reply to this message

Attachments:
Download 'sence.png' (200 KB)

Preview of image 'sence.png'

> IS there anybody can give me some advice??

Just a quick question to make sure it's not the obvious:

What max_trace_level setting do you use? Do you get any warnings about 
it? A max_trace_level which is too low will lead to black spots when 
used with reflection and or refraction.

Could be very well, though, that your problem has a completely different 
   source.


HTH,
Florian

Post a reply to this message

news:web.441fa27ddfe6af01598059850@news.povray.org...
As sayd Florian, try rising max_trace_level

BTW where did you get your mesh? a simulation?

Marc

Post a reply to this message

> i got a trianglar mesh file, and i render it with the "mesh2" object, the
> result can be seen in the attachment. But there so many black holes in the
> image.

Try "max_trace_level" like the others says.
And probably add "double_illuminate" ?
In POV-Help it says :
"A surface has two sides; usually, only the side facing the light source 
is illuminated, the other side remains in shadow. When double_illuminate 
is used, the other side is also illuminated.
This is useful for simulating effects like translucency (as in a lamp 
shade, sheet of paper, etc)."

Post a reply to this message

> Could be very well, though, that your problem has a completely different
>    source.

Another trouble could be that the normals don't point to the same side of
the triangle. I recall lighting issues when some of the normals of the
triangle were calculated clockwise and some counterclockwise when generating
them using my MMM with a faulty code.

Additionally, what's the size of your triangles? If they're *very* tiny, you
could run into the floating-point precision problem.

Regards,
Tim

-- 
aka "Tim Nikias v2.0"
Homepage: <http://www.nolights.de>

Post a reply to this message

thanks firstly,

i construct the mesh with marching cube algorithm based on a regular grid,
and the resolution of my grid is 80X40X100.

i check the online help of pov-ray, and it says: Typically values whose
absolute values are less than a preset value epsilon are considered false
for logical expressions. The value of epsilon is system dependent but is
generally about 1.0e-10. Two floats a and b are considered to be equal if
abs(a-b) < epsilon.

so maybe i should save my mesh file with double type, am going to try it,:)


"Tim Nikias" <JUSTTHELOWERCASE:timISNOTnikias(at)gmx.netWARE> wrote:
> > Could be very well, though, that your problem has a completely different
> >    source.
>
> Another trouble could be that the normals don't point to the same side of
> the triangle. I recall lighting issues when some of the normals of the
> triangle were calculated clockwise and some counterclockwise when generating
> them using my MMM with a faulty code.
>
> Additionally, what's the size of your triangles? If they're *very* tiny, you
> could run into the floating-point precision problem.
>
> Regards,
> Tim
>
> --
> aka "Tim Nikias v2.0"
> Homepage: <http://www.nolights.de>

Post a reply to this message

yes, a simulation

"Marc Jacquier" <jac### [at] wanadoofr> wrote:

> news:web.441fa27ddfe6af01598059850@news.povray.org...
> As sayd Florian, try rising max_trace_level
>
> BTW where did you get your mesh? a simulation?
>
> Marc

Post a reply to this message

thanks, good idea, i'll try~,


zorglub <zor### [at] e-garfieldcom> wrote:

> > i got a trianglar mesh file, and i render it with the "mesh2" object, the
> > result can be seen in the attachment. But there so many black holes in the
> > image.
>
> Try "max_trace_level" like the others says.
> And probably add "double_illuminate" ?
> In POV-Help it says :
> "A surface has two sides; usually, only the side facing the light source
> is illuminated, the other side remains in shadow. When double_illuminate
> is used, the other side is also illuminated.
> This is useful for simulating effects like translucency (as in a lamp
> shade, sheet of paper, etc)."

Post a reply to this message

"lien0n" <nomail@nomail> wrote:
> i got a trianglar mesh file, and i render it with the "mesh2" object, the
> result can be seen in the attachment. But there so many black holes in the
> image.

Just a guess, but could it have something to do with your REFLECTION values?
You have reflection {0.0, 1.0} as the min and max values.  The POV docs say,
"The minimum value is how reflective the surface will be when viewed from a
direction parallel to its normal..."  Here, the min value is 0...meaning
black (?) or no light reflection at all (?). Again, I'm just guessing, as I
haven't had occasion to use "minimum reflection" before, so I don't really
know *how* it works.

Ken

Post a reply to this message

i turned it to 0.5, and the result is much better~
 :)

"Kenneth" <kdw### [at] earthlinknet> wrote:
> "lien0n" <nomail@nomail> wrote:
> > i got a trianglar mesh file, and i render it with the "mesh2" object, the
> > result can be seen in the attachment. But there so many black holes in the
> > image.
>
> Just a guess, but could it have something to do with your REFLECTION values?
> You have reflection {0.0, 1.0} as the min and max values.  The POV docs say,
> "The minimum value is how reflective the surface will be when viewed from a
> direction parallel to its normal..."  Here, the min value is 0...meaning
> black (?) or no light reflection at all (?). Again, I'm just guessing, as I
> haven't had occasion to use "minimum reflection" before, so I don't really
> know *how* it works.
>
> Ken

Post a reply to this message