"Sabrina Kilian" <ski### [at] vtedu> wrote in message 
news:4b562a8a@news.povray.org...
> The narrow depth of field is not the only cue, and may not be the most
> powerful. What a tilt-shift lens also does is chance the way parallel
> lines appear. You can see the effect more dramatically when looking at
> pictures of architecture where, were you are the ground looking up, the
> sides of a building would appear to converge, a tilt-shift lens allows
> you to force them to be closer to parallel. When you are up close to a
> small cube, the lines you see appear parallel. The larger the object,
> the more the lines appear to converge.
>
> Another is the strange way the brain expects parallax to work at long
> distances, and the way it does when viewed through high magnification
> lenses.

Oh, I know tilt-shift is more complicated than that... I was really 
stretching an analogy too far, I guess. :-)

I was looking through a book the other night that was showing optical 
illusions, some very old and some very new. Some of the newer ones were done 
with computers and were modified by moving the shadows around. The article 
in the book was talking about how we're accustomed to mentally converting 2D 
images to 3D representations, and how the brain can be fooled. It got me to 
thinking about how much of visual art (in particular CG and film) is based 
on what the mass audience is trained to expect, rather than what is "real".

I had a discussion with someone a while back about "realism" in CG. She was 
trying to create a realistic looking puddle of blood for some horror image 
or other. She was unhappy with her results, and cast a net to try to get 
other ideas. A lot of people chimed in with simulating the viscosity of the 
fluid, it's reflectiveness, the way it changes color, and the way it, well, 
spatters. My suggestion was to put some red food coloring in some clear corn 
syrup, pour it on a cutting board or plate, and use that as a model. She 
thought that was wierd, but I pointed out that that's one of the most common 
sorts of "movie blood" (it's called Kensington Gore, IIRC) and that what she 
probably wanted was not "real" blood, but blood that looked like what they 
do in a movie, because that's the only kind (I hope) that most of us ever 
see. People who don't have to see large amounts of real blood mostly don't 
know what it really looks like (it's thinner than in the movies, and turns a 
boring brownish-red that has no sheen and looks awful [read: boring] on 
color film). She later said that that was exactly the look that she was 
trying to achieve, and she felt like it helped her image.

As with most of life, "realism" in CG seems to be about managing 
expectations. :-D

--
Jack

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