Gerard Tyra - SA Technology (gtyra++at++cts.com)
Sat, 25 Jan 1997 13:33:10 -0800 (PST)
>
> Gerard Tyra - SA Technology <gtyra++at++cts.com> said:
>
> > You have hit a problem that I have seen in everything from flight
> > simulators to animation systems, ie. lights/color values are clamped to 1.0.
> >
> > So here is my open wish list:
> >
> > 1) Allow values greater than 1.0 to be input and used in the
> > computation. After all, even a dark grey surface will look white if you
> > pump enough light into it.
>
> Woaaa - be very careful what you wish for. Suppose they did compute
> things the way you suggest. What would happen to a red surface with
> RGB values like (1.0,0.1,0.1) - presuming that the colour calculations
> are done indepenantly in RED, GREEN and BLUE - what would happen? The
> answer is that all three colour components could go over 1.0 and (presumably)
> be clamped to 1.0 for display. This would mean that the predominantly red
> surface would show up as white - but real-world diffuse reflectors don't
> change colours like that. (Don't get confused with specular reflectors -
> which are a different matter).
>
Here I beg to differ. Once the staurates, color starts to drop out of
the equation. And if the light only has a red component, you would still
get a red object, as long as the object has any red in its surface color.
> > 2) Give me 10/12 bit DACs on the IR. Then I can render a moon lit night
> > scene with values below 128 (or 0.5) but still "spike" the display with
> > values over 3000 for light sources.
>
> Building DAC's with high precision *and* high speed is a non-trivial problem.
True, but the same could be said of the DACs we are using right now. I
am currently aware of two commercial sources for such DACs. The business
issue for SGI is if enough people are willing to pay more to get the
extra dynamic range. I also know a lot of people in the pre-press
business who would love to have the better gamma correction of 12 bit color.
Gerry
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