clipka <ano### [at] anonymousorg> wrote:
> Am 22.01.2014 11:05, schrieb fomhorian:
> > I'm getting black lines & patches no matter what. :/
> >
> > Code:
> >
> > // +FN16 +BS5 +RP4 +RVP +am3 +a0.1 +r512 +ac0.999995 +w800 +h800
>                                 ^^^^^ ^^^^^ ^^^^^^^^^^^
>
> The settings interact as follows:
>
> The "+a0.1" setting specifies that you accept an error(*) of up to 10%
> per pixel. This is quite a lax setting, for high-quality renders I'd
> recommend "+a.01".
>
> (*The error margin is relative to 100% white for pixels somewhere
> between black and white; for brighter pixels, the error margin is
> relative to the resulting pixel colour itself.)
>
> The "+ac0.999995" setting specifies that you want a 99.9995% confidence
> that any given pixel is indeed within the accepted marging of error; an
> equivalent statement (at least in layman's terms) is that you accept
> 0.0005% of all pixels to be outside the accepted margin of error. This
> is an extremely strict setting, for high-quality renders I'd recommend
> something about "+ac0.99".
>
> The "+r512" option specifies how many samples you accept for any given
> pixel to be taken in the worst case; the value is not taken literally,
> but rather according to the formula:
>
>      max_samples = 4^r
>
> (The rationale behind this parameterization is that it is similar in
> order of magnitude as the effective maximum number of samples in
> anti-aliasing mode 2, while at the same time being easy to express as a
> formula.)
>
> I guess I don't need to tell you that 4^512 (= ca. 10^308) is much more
> than you'll ever need, and in a worst-case scenario could stall your
> render for just a bit short of eternity. For practical purposes, "+r9"
> should be enough for any render.
>
>
> To sum it up, for practical purposes the following settings should be ok
> for high-quality renders:
>
>      +am3 +a0.01 +ac0.99 +r9
>
>
> If you experience excessive noise, try lowering the "+a0.01" setting.
>
> If you experience stray dot artifacts, try increasing the "+ac0.99" setting.
>
> Further increasing the "+r9" setting should typically not be necessary.
>
>
> That said, it seems that you indeed have spotted a problem in UberPOV,
> but it's not related to blurred reflections. Somehow, the perturbed
> normals of the plane appear to lead to nonsense results very close to
> the horizon, leading to invalid colour values for individual rays, which
> sort of "dominate" the results for any other rays shot for the same
> pixel and (in the Windows version) manifest as pitch black pixels. (In
> the Linux version, they may lead to bright white pixels instead.)
>
> I'll have to investigate whether these nonsense results are indicative
> of an actual bug that needs to be fixed, or rather rare but inevitable
> consequences of rounding errors that can safely be worked around.

Well; I usually render with +a0.005, & I did start with +ac0.95...
I was surprised that POVRay could take +r512 actually & it still rendered way
quicker than my standard aa-settings & +AM2. Might it be possible for UberPOV to
have an adaptive range for the +r? Something like +ra9,512...

                                             Cheers from Sweden!

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