Phil Clute wrote:
> 
> Maybe someone else has tried this, or maybe I'm alone in my stupidity
> but I tried to render an earth to scale 1pov unit = 1 meter which of
> course comes
> out to a mean value of 12,756 km in diameter or 6,378,000m as a sphere
> radius.
> Also, I put my light source(the sun) at <0,0,0> and then moved my earth
> sphere
> to <0,0,149600000000>(mean distance from sun).
> 
> 1.What is the limit? How many places can I carry out my numbers around
> the decimal point?

 Whatever your system's epsilon will support. I forget what the numbers
are on a system by system basis. There was a mention that the Pov team made
a change increasing the value it now supports in the release of Pov v3.15e
They had choosen a lower valu previously and many users complained so they
extended it's capability some. Check in the announcements group and see
if the release notes give the upper value for that.

> 2.Why does the earth appear to have a grainy texture when it is only has
> a blue
> pigment? Scale is beyond pov's capabilities?

Posibility.
 
> 3.I was surprised that the earth was actually lit up at that distance.
> Is this because
> there is no falloff in the point lightsource?

Yes.
 
> 4.I also wanted to be able to rotate the camera around the earth but
> couldn't
> seem to make it work. I tried rearanging the order of the code with
> rotate
> before or after translate to no avail. How would this be accomplished?

camera { location < 0, 0, -120,000,000> look_at 0 rotate y*360 }
 
> Note: I know doing it at this size really isn't necessary. I just wanted
> to give it a shot!

Bob Hughs did a rather extensive study on this issue of distance within
the last 3-4 months or so. I forget where he psted his results but
a little searching should be able answer your questions in more detail.

It was probably posted to this group. If not look in
.tutorials
.windows
.scene-files

-- 
Ken Tyler

mailto://tylereng@pacbell.net

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