Ive:

Here is another one.  You know, your HDR comes through as being
really dark, much darker than the reference probes.  I had to turn the
ambience up in order to get just the illumination that you see here.  Any
idea why that might be?

Aaron

Aaron Gillies
New York City
x3rxes[^]yahoo.com

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> Here is another one.  You know, your HDR comes through as being
> really dark, much darker than the reference probes.  I had to turn the
> ambience up in order to get just the illumination that you see here.  Any
> idea why that might be?
>

Well, this was my first experiment with a more complicated HDR scene
than just a box. And it seems that producing good HDR images with
PoV requires some experience than I already have.
The original LogLuv image did also store a so called STONITS information.
This can be used to calculated the physical brightness for each pixel in
candelas/squaremeter but this info was lost when transformating the image
to the radiance HDR format. But I'm not even sure if the stonits was
calculated correct. And as this image with the 'poor' radiosity settings
(samples 500, error_bound 0.3) took already about 3 days to render
on my old machine I am meanwhile a little bit bored in experimenting
with it. But for sure I will continue the work sooner or later (maybe
later, because I need a faster machine) so I have thought I do post this
little experiment to see if it somehow works for you.

And thanks a lot for trying it :)

-Ive

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> You can send it to me if you want - someone from the Megapov Team might
> find the time to work on it so it can be included in Megapov.

Great. I will try to at least do clearly indicate the parts I have changes and add
some comments. As soon this is done I will send it.
And I guess hdr output is not only useful for creating global illumination maps.
It should also work fine in combination with a program like your HCR-Edit
to have the possibility to apply gamma and exposure control after the render
process but with the full range of data.


> If continued trace does not work i assume you have not yet implemented the
> Read_Line() method.

Right. :)

-Ive

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3e63aaf2@news.povray.org...
> > Here is another one.  You know, your HDR comes through as being
> > really dark, much darker than the reference probes.  I had to turn the
> > ambience up in order to get just the illumination that you see here.
Any
> > idea why that might be?
> >
>
> Well, this was my first experiment with a more complicated HDR scene
> than just a box. And it seems that producing good HDR images with
> PoV requires some experience than I already have.

I've played with many HDR image now and it seems that there's no real
standardisation about their ambience value. Some are very light and some are
very dark, at the point that they must be corrected in HDRShop just to see
something else than pure white or pure black... Eventually, I always have to
tweak the ambient value to get nice results. I wouldn't worry to much about
this, as long as the image is usable (which is the case here).

G.


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