> 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,:)

That's not what I meant. But if you lose very low floating-point values,
like the online help says, things will be considered equal and triangles
might get dropped. It sometimes help to multiply all numbers with 10, 100 or
1000 (depending on the small scale of the mesh) when exporting it, and try
scaling it down (though you could still run into the same problems).

All that aside, there's still the issue of max_trace_level and
reflection/refraction to be considered, you easily get black dots on
transparent objects that are a little more irregular than a sphere...

Regards,
Tim

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

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but i also tried others' idea for changing the max_trace_level to be 20, and
the result appears excellent, though the render speed is slow, and am going
to seek for appropriate values for the max_trace_level and min reflection.

thanks, everyone, your ideas are so helpful~~~~,

"lien0n" <nomail@nomail> wrote:
> 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

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news:web.44210cddb0f87641598059850@news.povray.org...
> but i also tried others' idea for changing the max_trace_level to be 20,
and
> the result appears excellent, though the render speed is slow, and am
going
> to seek for appropriate values for the max_trace_level and min reflection.


In addition to max_trace_level, you could want to tweak adc_bailout, I
suggest you have a look at the doc on this topic
I quote
"The point at which a ray's contribution is considered insignificant is
controlled by the adc_bailout value. The default is 1/255 or approximately
0.0039 since a change smaller than that could not be visible in a 24 bit
image. Generally this setting is perfectly adequate and should be left
alone. Setting adc_bailout to 0 will disable ADC, relying completely on
max_trace_level to set an upper limit on the number of rays spawned."

you could rise  adc_bailout to get shorter render times

Marc

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Hi,

> in my mesh file, there are three data blocks: vertices, normals, and
> triangles' vertex indices. I am sure that the vertices and the trianlges'

Just a thought: how about taking one vertice from every triangle and 
making a small blob from it? this way all the water should be much 
smoother than made from triangles... Never tried it before though.

cheers
-- 
Piotr "utak3r" Borys

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