Dave Cook wrote:
> 
> Even when you do come across images that are suitable for mapping onto a
> sphere, they're usually preprocessed to show shadows, rather than as an
> actual heightfield. You can see how the shadows in the upper right of the
> earth are very pronounced, where the lighting should in fact be pretty flat.
> It still gives a good illusion of reality, but it's even better when we
> POV'ers can get our hands on the real raw data and not preprocessed images.
> That's why I thought Jon Berndt's find was so cool - the lights at night
> render well without artificial shadows. I only wish I could find the TIFF
> version without the JPEG artifacts :(

	I agree with all that and the one used appeared to be from equatorial
orbit and faked to expand the poles to mercator projection and then put
back again for the image. 

	But as to light, I am finding that problem in POV where effectively
infinite light sources do not illuminate half a sphere. It is probably
something in the pixel resolution issue. By that I mean the larger the
rendering (4 million by 3 million pixels and up) the closer the dividing
line gets to half and half light and dark. 

	As to TIFF without JPG artifacts, I would rather wish people would
learn how to us JPEG compression. I don't mean to be obnoxious but I
spent my time in hell learning how to use it and I have seen the results
of others who have also. And it is not helped by JPEG compression ratio
being a meaningless number. 

	Look at the largest night time image and see the "dark" Sahara is
generally purplish. 

> "Matt Giwer" <jul### [at] ijnet> wrote in message
> news:3A25A1D7.C20D63C3@ij.net...
> > Dave Cook wrote:
> > >
> > > I enjoyed Jon Berndt's recent posting of the mosic of the earth at night
> > > wrapped around a sphere, so I went off to see what else is new NASA and
> > > GSFC. I stumbled across this image and, when I took a look a the 3Kx3K
> TIFF
> > > version, I realized it might benefit a number of people who have been
> trying
> > > to do accurate earth renderings. In particular, the atmospheric effects
> at
> > > the edges of the earth are rather nicely done. This image is, as the
> > > accompanying text on the Web site
> > > http://rsd.gsfc.nasa.gov/rsd/bluemarble/index.html explains, a
> compilation
> > > of satellite imagery and data. The large TIFF version is about 13Mb, but
> the
> > > details are astounding.
> >
> > Yes but they don't give the raw image. Those bastards! Hope their name
> > is Kenny.

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