On Sun, Nov 11, 2012 at 1:41 PM, Renk Thorsten <thorsten.i.r...@jyu.fi>wrote:
> > I suspect the difference in light intensity
> > (dynamic range) doesn't fit in an 8-bit 3-component color.
>
> It sure doesn't, but I think you're thinking way too complex. We don't
> want to render physical light intensity, we want to render perceived light
> intensity, and there the Weber Fechner law is relevant, and that says that
> we roughly want to render the log of the physical light intensity.
>
> For instenace, full daylight has 10,000 lux, and a very dark overcast day
> has 100 lux - yet if you multiply the sun (rgb) = (1,1,1) which works fine
> for a sunny day with 0.01, you don't get an overcast day - 0.6 is more the
> factor you need, i.e. every factor 10 reduction in luminous flux is about
> -0.2 from the base light.
>
> A full moon has about 0.1 - 1 lux, so we get (rgb) values of ~(0.1..0.2)
> in the light vector - which works visually just fine (I've been using
> vec3 moonLightColor = vec3 (0.095, 0.095, 0.15) * moonlight * scattering;
> for the pics) - which gives imo a decent visual appearance.
>
> You need to do High Dynamic Range rendering to accurately capture these
differences and the eye's ability to adapt to them. Basically, you do all
the rendering in floating point and at the end convert the values to RGB
colors with a mapping operator. We don't do that yet.
Tim
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