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I hate to keep beating on this point, but I still think the geometry is
confused.
I will try to explain it as clearly as I can and you can tell me where I go
wrong.
Lets define the earth's orbit as a plane. The sun is also on this plane,
and in 99% of the illustrations of the system the camera is also in the same
plane. So far so flat.
The earth's spin axis (through the north and south poles) is not
perpendicular to this plane. It is tilted by 23.5 degrees.
The moon is also not in the solar plane, but I will take your word for the
angle.
So I guess what a photo would show is a vertical terminator that does not go
through the north and south poles. I hope that makes sense. I have
attached a tiny bitmap to illustrate the geometry.
In June everything north of the arctic circle is closer to the sun than the
day/night terminator, which is why the sun doesn't set in the arctic in the
summer.
In the December you get the exact opposite effect so the antarctic is in
perpetual daylight and the arctic has perpetual night. Spring and fall are
obvious interpolations.
Enough geometry, on to POV :-)
If you model the earth as a single sphere with a single texture and light it
from the "sun" you should be able to produce still shots and animations
easily.
If you choose to use the "two textures" method things will be much trickier.
You might be able to produce a snapshot by careful splicing of the day/night
textures on the sphere, but a one-day animation (spinning earth) would
require a geometry genius.
I hope you will take all of this in the spirit it is intended. I really
like your picture and I want to encourage you to produce one that combines
the artistic merit you already show with an accurate geometry. I wish I
could do so well.
"Matt Giwer" <jul### [at] ij net> wrote in message
news:3A3D788B.EF61EA76@ij.net...
> You get it tilted.
> --
> Americans fought Germany in WWI and WWII
> because they were forced to by the draft.
> -- The Iron Webmaster, 401
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Attachments:
Download 'earth.bmp.dat' (9 KB)
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