"Hugo Asm" <hua### [at] post3teledk> wrote in message
news:41155258$1@news.povray.org...
>
> Thanks for posting the extra renders. Is it true that both the daylight
> rendering that you posted yesterday, and the no_rad version you posted
> today, are without radiosity? Because they look the same to me.

The first did have radiosity. It's just not plainly obvious because I tried
a brightness of 0.8 and gray_threshold 0.4 to lessen the color bleeds. Maybe
if you were to examine the upper middle roof edge, where it crosses over the
lower roof, you might see it is whiter toward the right side due to the
diffusion effect between the two roof levels. It changed drastically from
yellow-white to pure white if I left those values as default.

> The entrance-artifact that you mention could be due to a wrong value in
> reflection_exponent (for example, if you wanted to write .8 you might have
> written 8 ... it was late at night you said) or max_trace_level was set
too
> low. Usually, radiosity will not have much effect on glassy surfaces
because
> they provide very little diffuse reflection. They are mirror-like, and
> refracts the light, both of which are independant calculations from
> radiosity.

Good point. Nope, not the case, unfortunately. Now I've managed to see the
artifacting again so I attached another image. Both renders are subjected to
the problem, the top one has radiosity and the lower does not (merely
speckles by comparison). This happened after adding back in 'exponent' to
every reflection statement, all but the brick has at least some reflection.
I better speak up about the reflection_exponent no longer being used, it's
only 'exponent' now in 3.6, even though the Editor still recognizes the old
keyword. I had thought it was removed until you mentioned it. #version
directive has no affect.

> Yeah but I've found the exposure control is addictive.  :-)  Anyway it
takes
> a bit of practice because one must think about light in a more realistic
> manner. I think most of us are still used to think directly about, what we
> see on the screen (or what we see on photos ... all of which are images
> limited/compressed to a low dynamic scale). Real world is different.

Yep. I'd like doing some of that, too, just haven't gotten around to
MegaPOVing again.

> I could try to give some suggestions but they would involve changing all
> texture values and strength of light_source's, along with using exposure
...
> maybe the simplest solution for now, is to further increase the
radiosity -
> brightness value. Remember you can go above 1.0 and I would recommend 1.3
or
> 1.6... I've had fairly good results with that, and the results were at
> least, that the shadows weren't black anymore. (It may pick up too much
> light from the walls then, but anyway ... you could add a blue fill-light
to
> compensate a little for that)

Probably... probably... Although, I would like more contrast for night and I
think dark shadows in daytime is a good thing if in the right places. Most
likely I've used too extreme a diffuse on everything while I tried to get
the nighttime lighting. Afterall the roof is diffuse 0.9 (bricks are 0.5 and
mortar 0.67) and so is as bright as fresh snow when in reality it's less
white. That's what happens from a tendancy to use any number that seems to
fit at the moment.
:-)
Thanks for the suggestion to try MP's exposure with this scene. I'll be
thinking about it.

Bob H.

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