=?ISO-8859-1?Q?J=F6rg_=27Yadgar=27_Bleimann?= <yaz### [at] gmxde> wrote:
> So I carefully worked through the steps described there - but when I
> came to the final setting (see code below), I noticed that my scene
> matched Mrs. Andresdottir's example scene as far as brightness of the
> shadowed parts is concerned - but still contained considerably more
> artifacts than her really clean scene (seventh from top, just above the
> version with area_light).

I cannot explain why Andresdottir's render is cleaner than yours.  I can say
that, in my experience, a really tiny pretrace_end is good for reducing
artifacts.

> In her tutorial, Mrs. Andresdottir does not give the version of PoV-Ray
> she used, as her original code contains a switch for versions newer than
> 3.1, I assume that it is 3.5 rather than 3.6 (which I use). Could it be
> that 3.5 uses different default radiosity settings than 3.6? Or is it
> because Mrs. Andresdottir places the whole scene inside an (monochrome)
> ambient 1 sphere rather than a gradiented sky_sphere?

I have no experience with 3.1, so I can't comment on that.  It is not a question
of any difference in the defaults between 3.5 and 3.6, as all the parameters are
specified.  I do not recall any difference in output between 3.5 and 3.6.  I
don't think there's any difference between a sphere and a sky_sphere, although
someone else will have to confirm this.

I am no expert at radiosity, but I question some of Andresdottir's settings:

>          brightness 1.5

This is physically unrealistic.  A high brightness value can compensate for a
low recursion_limit, but that's obviously not the case here.  I suppose that
this looks more "realistic" because a straight rendering does not capture the
dynamic range of real-life lighting.

>  error_bound 0.05

I've found that setting error_bound this low does nothing more than slow down
your render, and perhaps add more intractable artifacts.

>  recursion_limit 5

See the tutorial in the documentation.  There's no reason to set recursion_limit
this high, unless you enjoy waiting for stuff.

>  pretrace_end 0.01

I found that this works well in 3.6, but when you upgrade to 3.7, it won't be
small enough for many scenes.

>          load_file "whatmough_residential.rad"
>  save_file "whatmough_residential.rad"

I'm not sure what it means to load_file and save_file at the same time.  (I
vaguely recall that there's some trick that this effects, but it wasn't
fantastic enough for me to retain it.)

Good luck!

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