I'm trying to do a scene with two objects, looking along z, one at z=-5
(which I want to be in focus) and the other at about z=30 (which is out of
focus).

Camera is set:

camera {
 perspective
 angle 45.0000
 right < 1.0, 0, 0>
 up 1.47*y

 location cameralocation
 look_at <0,2,0>
 aperture 0.5
 blur_samples 10000
 focal_point<0,0,-5>
}

Even using that many blur samples, there are still artifacts in the distant
object.

Any ideas on how to get a smoother blur on the distance object?

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"Andrew Rowson" <pov### [at] growsecom> wrote in message
news:3ec646c7$1@news.povray.org...
> I'm trying to do a scene with two objects, looking along z, one at z=-5
> (which I want to be in focus) and the other at about z=30 (which is out of
> focus).
>
> Camera is set:
>
> camera {
>  perspective
>  angle 45.0000
>  right < 1.0, 0, 0>
>  up 1.47*y
>
>  location cameralocation
>  look_at <0,2,0>
>  aperture 0.5
>  blur_samples 10000
>  focal_point<0,0,-5>
> }
>
> Even using that many blur samples, there are still artifacts in the
distant
> object.
>
> Any ideas on how to get a smoother blur on the distance object?


Sorry, I should add that stupidly small variance and a confidence value of 1
still give a grainy blur.

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Do you have a image to show the graininess? A crop of the particular part
would suffice. Post it to the povray.binaries.images group if you do,
please. I get acceptable results using default confidence and variance at
100 samples. Perhaps yours is a specific circumstance or large rendering?
The problem wouldn't seem to be the camera's aspect ratio, at least.

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Hughes, B. wrote:
>Do you have a image to show the graininess? A crop of the particular part
>would suffice. Post it to the povray.binaries.images group if you do,
>please. I get acceptable results using default confidence and variance at
>100 samples. Perhaps yours is a specific circumstance or large rendering?
>The problem wouldn't seem to be the camera's aspect ratio, at least.
>

Yes, post a sample image.  But from the sounds of this, I ran into this same
problem three or four years ago with focal blur in POV 3.1.  The problem is
the adc_bailout.  What this does is says that if after so many samples, a
new sample probably (or can't) change the color by more than such an
amount, then stop tracing rays.

The even bigger problem is that adc_bailout had a bug that basically resets
it to the default 1/255.0 every time you render an image.  I finally
reported the bug a couple months ago, and it's patched in 3.51, but I don't
know if there's a binary patch yet.  However, if you have the source code, I
can help you make the changes necessary to make the adc_bailout work.  Just
set it to 0, and artifacts like this should disappear (assuming that's what
you ran into).

Another option is to post the source in povray.text.scene-files, and I can
render it with my "fixed" version to verify if that is indeed the problem.

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"Retsam" <nomail@nomail> wrote in message
news:web.3ecbc05f7e2294662a3ff2e70@news.povray.org...
> Hughes, B. wrote:
> >Do you have a image to show the graininess? A crop of the particular part
> >would suffice. Post it to the povray.binaries.images group if you do,
> >please. I get acceptable results using default confidence and variance at
> >100 samples. Perhaps yours is a specific circumstance or large rendering?
> >The problem wouldn't seem to be the camera's aspect ratio, at least.
> >
>
> Yes, post a sample image.  But from the sounds of this, I ran into this
same
> problem three or four years ago with focal blur in POV 3.1.  The problem
is
> the adc_bailout.  What this does is says that if after so many samples, a
> new sample probably (or can't) change the color by more than such an
> amount, then stop tracing rays.
>
> The even bigger problem is that adc_bailout had a bug that basically
resets
> it to the default 1/255.0 every time you render an image.  I finally
> reported the bug a couple months ago, and it's patched in 3.51, but I
don't
> know if there's a binary patch yet.  However, if you have the source code,
I
> can help you make the changes necessary to make the adc_bailout work.
Just
> set it to 0, and artifacts like this should disappear (assuming that's
what
> you ran into).
>
> Another option is to post the source in povray.text.scene-files, and I can
> render it with my "fixed" version to verify if that is indeed the problem.
>

I managed to fix this by specifying the varience as 0. Looks fine now.

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