Hi, Alain, thanks for posting these tips. I do have some questions (of
course!):

Alain <ele### [at] netscapenet> wrote:

>
> > brightness 23
> Default to 1. It's a multiplicator for the returned radiosity samples. Without
> this, your scene would be almost all black.

For some not-yet-understandable reason (perhaps because the light_sphere is
so small)  I HAD to pump the brightness up, otherwise the scene was just
way too dark. But this surely interacts with other values, so perhaps it
should be lowered, and some other things adjusted.

> > pretrace_start .08 // default value
> Shifting this "may" help you getting rid of some artefacts near corners like
> dark spots along inside corners.

Shifting it up ot down?  Is it better to use a higher value for this or a
lower value?

> > pretrace_end .01
> Lowering this may enable you to use more relaxed settings elswhere, possibly
> lending to somewhat shorter render times.

I'll try that.  Lower values do produce a drastic difference in smoothing
things out. But does a lower value also make subtle artifacts more visible
and
pronounced? It seems to, but my eyes may be playing tricks on me.

> > max_sample 1.0
> This puts a cap on the brightness. Not importent in your case as you apparently
> don't have any object with a brightness larger than 1.

I'm a bit fuzzy on this: Does it control the brightness of rays shot from
the light source, or the brightness of BOUNCED rays? Or both?? I thought it
would keep any area of the scene from exceeding a certain brightness, but
that doesn't seem so; I can easily "wash out" areas of the scene closest to
the light sphere if I'm not careful. So, I don't really understand what
max_sample does.

> > low_error_factor .025 // half the default
> 1/20 the default of 0.5.

Sorry, I don't understand that. Explain?

> > always_sample off
> Why? Default to "on". Only relevant if you do multi-pass or distributed render.

I've found that the quality gets better with it off--at least in this
particular scene. It's a subtle difference, but it's there.
> >
> You may try lowering brightness to 1 and bump up the pigment or ambient of the
> small ambient light sphere.

Yes, that does help. I'll work with the idea.

Ken W.

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