I have been trying to get rid of large black dots in some glass objects.

I have the following in my global settings :

global_settings {
  assumed_gamma 1
  max_trace_level 32
  max_intersections 128
..
..
..

an example of what I mean may be seen here :

    http://www.blastwave.org/dclarke/povray_AMD64/media1_001.png

any ideas ?

Dennis

Post a reply to this message

"Dennis Clarke" <dcl### [at] blastwaveorg> wrote:
> I have been trying to get rid of large black dots in some glass objects.
>
> I have the following in my global settings :
>
> global_settings {
>   assumed_gamma 1
>   max_trace_level 32
>   max_intersections 128
> ..
> ..
> ..
>
> an example of what I mean may be seen here :
>
>     http://www.blastwave.org/dclarke/povray_AMD64/media1_001.png
>
> any ideas ?
>
> Dennis

Hmm, yes, I've got the same, only worse:
http://i21.photobucket.com/albums/b288/aardpast/Real%20pics/RingsMaxTrace20.png
I've tried cranking up Max Trace level to 50, but the result doesn't change
much, in fact it's slightly worse in places. I even tried a Max_trace_level
of 250, which is just as bad.
I have two spotlights that are inside the ruby, if I move them outside the
ruby, the black spots disappear. No amount of looks_like or union of the
light and the ruby changes anything. An adc_bailout of 0 with max trace of
level 200 doesn't seem to ever get to the ruby. And adc_bailout of 1/200048
with Max trace of 50, is a *lot* worse, with black dots peppering the ruby.
It looks like the only thing that works is to make sure your lights aren't
contained in any solid objects. Reducing media might possibly work too.

Post a reply to this message

Grassblade nous apporta ses lumieres en ce 18-12-2006 17:34:
> "Dennis Clarke" <dcl### [at] blastwaveorg> wrote:
>> I have been trying to get rid of large black dots in some glass objects.

>> I have the following in my global settings :

>> global_settings {
>>   assumed_gamma 1
>>   max_trace_level 32
>>   max_intersections 128
>> ..
>> ..
>> ..

>> an example of what I mean may be seen here :

>>     http://www.blastwave.org/dclarke/povray_AMD64/media1_001.png

>> any ideas ?

>> Dennis

> Hmm, yes, I've got the same, only worse:
> http://i21.photobucket.com/albums/b288/aardpast/Real%20pics/RingsMaxTrace20.png
> I've tried cranking up Max Trace level to 50, but the result doesn't change
> much, in fact it's slightly worse in places. I even tried a Max_trace_level
> of 250, which is just as bad.
> I have two spotlights that are inside the ruby, if I move them outside the
> ruby, the black spots disappear. No amount of looks_like or union of the
> light and the ruby changes anything. An adc_bailout of 0 with max trace of
> level 200 doesn't seem to ever get to the ruby. And adc_bailout of 1/200048
> with Max trace of 50, is a *lot* worse, with black dots peppering the ruby.
> It looks like the only thing that works is to make sure your lights aren't
> contained in any solid objects. Reducing media might possibly work too.





adc_bailout 0 turn it completely off as any change is larger than 0.
A value of 1/200048 is ridicously small, still to small if outputing as 48 bit 
PNG or TGA. In this case, the floor value is 1/65536, as it's the smalest 
difference you can find.
Instead of making adc_bailout smaller, try to make it LARGER! Try adc_bailout 
1/128 or 0.01 to start.
This works best when coupled with some contained media or some fade_color.

-- 
Alain
-------------------------------------------------
Don't cry because it is over, smile because it happened.

Post a reply to this message

"Dennis Clarke" <dcl### [at] blastwaveorg> wrote:
> I have been trying to get rid of large black dots in some glass objects.

  Perhaps the object is simply refracting some black part of the scene?

  If you have some big black or very dark area in your scene, try changing
its color to something else to see if the black spots change too. If they do,
the reason is rather obvious.

Grassblade <nomail@nomail> wrote:
> Hmm, yes, I've got the same, only worse:
> I've tried cranking up Max Trace level to 50, but the result doesn't change
> much, in fact it's slightly worse in places. I even tried a Max_trace_level
> of 250, which is just as bad.

  Try the same thing as I suggested above first. If you don't have anything
black or changing the blackness to something else doesn't affect the dots,
then it might be something else.

-- 
                                                          - Warp

Post a reply to this message

Warp <war### [at] tagpovrayorg> wrote:
> "Dennis Clarke" <dcl### [at] blastwaveorg> wrote:
> > I have been trying to get rid of large black dots in some glass objects.
>
>   Perhaps the object is simply refracting some black part of the scene?
>

  I don't think so.  At least, I don't see how.

  The scene has smooth lighting and no other objects in the scene.  There
are the central three objects, the overhead lights, and the walls.  Nothing
else.

besides ... why would it show up as a speckle of black dots and not an
actual refracted object ?

dc

Post a reply to this message

I don't have any black in the scene. There is a blue skysphere
surrounding everything.
After trying everything I could think of with adc_bailout and max trace
level, I think I finally found out what was the problem: I was using a
media statement with multiple densities (3.6.2.3.4). With no direct
lighting to provide some colour, a few spots had 0 colour. I still don't
understand why it didn't antialias with surrounding pixels (I was using AA
0.3) though.
So, work around: add a weak light, so that all points have some light, or
split your media statements, although that will affect the final media
result.

Post a reply to this message