I really like this kind of idea.  Nice explaining of it.
This sort of thing is what makes getting great skies with foreground
subjects so difficult when taking a photograph. Fill lighting and filters
are what help to do that instead of being able to just snap a picture.
I would think human vision does some of this too.
Even though the pupil controls the majority of "emulsion" on the retina
I'd guess it also shuts down or boosts the amount of light at the back
of the eye to some extent.
Speaking of this, where I went today for the Easter picnic was a campground
which has a large cave.  At one point the tour guide shut off all the lights
and you don't see anything but the remnants of what was previously seen.
Just a little after the lights were out I was waving my hand in front of my face
proclaiming I could see it and I was promptly ignored.
Really though, I saw not a dim hand in front of my eyes but instead a totally
black silhouette of it, as though the cave had light in it at imperceptible
levels.  I turned around just afterward and noticed a ever brightening bluish
glow from a small spot.  It was the place we exited to after the lights were
back on.
Anyway, back to POV ;-) the way a person gets non-linear changes now
is to use ambient and diffuse, pigment color and gamma in various
relations I suppose.  That way you suggest sounds intriguing even if I can't
understand how anyone would go about it.

Bob

"Glen Berry" <7no### [at] ezwvcom> wrote in message
news:TUgDOeHcwtbl7VCZwbG2XphrPOQ2@4ax.com...
| If I remember correctly, Nathan said that the rendered image exists in
| floating point format before it is converted to the final image
| format. Would it be possible to gain access to the floating point
| values? I'd like to be able to specify my own formula for converting
| the floating point value to an 8bit integer.
|
| Why? I want to alter the linearity of the translation from floating
| point to integer. If you look at a plot of photgraphic film's response
| to light, it isn't linear. There is a certain threshold that must be
| achieved before any image is recorded.  Above that, the response is
| somewhat linear, until we get to the brightest exposure levels. In the
| highlights, increasing the exposure has less and less of an effect.
|
| In other words, the darker picture elements are expanded in dynamic
| range (higher contrast), and the brighter elements are compressed in
| dynamic range (lower contrast). One of the effects of this would be
| the ability to render light sources and not have them "wash out", or
| lose detail,  quite so easily. I think that adjusting the response
| curve to approximate film would also make the image look more
| realistic in general.
|
| I'm not sure yet if the human eye responds to light intensity values
| in a similar non-linear way, but I think it does. I know that human
| hearing is non-linear in its perception of dynamic range, but I can't
| say for sure about human vision yet.
|
| If anyone needs more of an explanation of what I'm talking about, I'll
| be more than happy to scan some charts for you and explain further.
|
| Thanks,
| Glen Berry

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