"Jim Charter" <jrc### [at] msncom> wrote in message
news:421600a9$1@news.povray.org...
> Lance Birch wrote:
>
> > I think the biggest way to improve the image (in my opinion) is with the
> > lighting.  Right now the image appears a little flat and therefore it's not
as
> > dramatic as it could (and deserves to) be.  I'd really love to see this
scene
> > taken further!  There's no reason to stop now since there's already been so
much
> > work put into it; just a few changes to the lighting of the scene could make
a
> > huge difference I think.  If it was my scene I'd probably drop the camera
height
> > a tiny bit as well, or if not, introduce some focal blur to separate the
> > background from the main subjects (heh, yes, I know... rendertime++)
> >
>
> Thankyou for the insights, and even more, the spirit of support.  In a
> nutshell, it is hard for me to give up on the backlighting.  The
> original vision was of the scene taking place in a gloom set against a
> backdrop of turgid, oppressive light, screened by a silhouette of jungle
> growth. That is not quite how the scene turned out, but I still cling to
> certain of its original aspects. I will try to swallow my conceptual
> arrogance and, if I ever find that new level of maturity, try the scene
> with some different lighting.  Parenthetically, I believe I have run up
> against this difficulty in contests before.  I think I just have a taste
> for the slightly flattening effect of halflight and backlighting that is
> a little at odds with the raytracing aesthetic. So I also wonder if some
> adjustment of the finishes might bring up the textures and still give me
> that backlight.

Well, I don't mean to say "abandon your concept"... just that it needs some
tweaking to get it to work how you want it to :)  A lot of the problems I find
with lighting are due to contrast.  Our eyes detect contrast before anything
else, so it follows that an image that lacks contrast is not as easy to view
(objects don't stand out as much, or the image looks flat).  However, you can
still have a backlit or post-sunset scene and still have contrast.. the key is
not introducing "global contrast", but instead introducing "localised contrast".
That is, contrast between the different objects and the background, not an
increase in contrast of the entire image.

To understand the difference between local and global contrast better, load your
image up in a graphics package like Photoshop or similar that supports a live
Histogram view.

1. apply say +10% Contrast to your image and watch what happens to your
Histogram... the low ends will move lower, and the high ends will move higher.
This changes the look of your image overall (and suddenly it doesn't look like
the kind of lighting you want, but the objects are separated better from the
background).

2. go back to the original image without the Contrast added, and this time apply
an Unsharp Mask to the image with a radius of 20 pixels and an amount of 20%
(with no threshold), and watch how your Histogram... you'll see that it doesn't
change very much at all (thus retaining the overall look of the image), however
the objects are separated better from the background and the image appears
slightly more "alive".  The reason is that localised contrast has been
introduced.

This is basically what our eyes do when we look at something in real life... as
we move our eyes, they adjust to the localised brightness level of what we're
viewing to create more contrast locally.  In other words, everywhere we look
there's contrast created locally, even though if we stood back further and
looked at the scene overall with relaxed eyes, it might not have a lot of
contrast and details would be harder to make out.

So the trick is to try to get the same thing to happen straight out of POV-Ray,
and the easiest way of achieving localised contrast/separation between objects
(the grass is a good example of where this is needed as right now it's difficult
to gauge its depth due to the consistency of luminosity) is to introduce
shadows, or use other tricks like fog to tint objects that are at great
distances (thus separating foreground from background), or use depth of field.
So in other words, we have to cheat a bit :)  You could make the backlighting
even more dramatic, and introduce a fill light to ensure the subjects are still
lit appropriately (in real life our eyes do a good job of simulating fill lights
in such conditions of backlighting, again this is the localised contrast
syndrome).

Another good way of testing where your image could use additional localised
contrast (or different lighting, fog to separate background/foreground, etc) is
to simply blur your eyes while looking at it; are the object depths still
obvious or do they appear to be floating in seas of colour?

I hope this all makes some sense :)

What I'm getting at is:  you can still retain the look of your image, but to do
so and still make the objects stand out you need to either introduce localised
contrast in the lighting of the objects, or use another technique to separate
the different objects from the background (by introducing a fog to tint the
background, or by using depth of field, etc).

Lance.

thezone - thezone.firewave.com.au
thehandle - www.thehandle.com