I mean absolutely no offense to anyone, since I hope we are all in
this game together, learning from one another.  But, I have noticed a
distinct deficiency in many outdoorsy POV scenes I have seen people
upload at various places:  the sky.

Here's the way I make a POV sky:

Use the Blue_Sky3 texture in the included texture file.  This texture
is typically ignored when people make skies, but I have found that if
you scale up the texture A LOT (thousands of times) it looks really
good.

Next consider the real world (well almost real, let's assume we have
a mostly clean atmosphere).  The sky is not the same color above
your head as it is at the horizon.  Even without pollution, things
like water vapor in the air scatter the light so that the sky is
lighter ("whiter"?) near the horizon.  Therefore, we'll add some fog
to the POV scene, and set the fog distance high enough that it only
affects things very far away.

The next thing is to figure how to implement it.  Mapping the sky onto
a flat plane perpendicular to the ground (like a lot of the POV samples
do) just makes it look like the sky was mapped onto a plane behind the
scene, not like a real sky.  All the clouds are the same size, so the
horizon seems like it's just a few feet behind the objects in the scene.

Make the ground plane as usual.  Then make a plane PARALLEL to it for
the sky.  Think about the Earth:  you are so small compared to the
size of the Earth that the ground and sky may as well be planes and
not spheres.  I have also made a HUGE sphere for the ground and a
larger one for the sky, in an effort to be truly realistic, and it
works, but isn't really necessary.

Making a ground plane and a sky sphere does NOT work, since that puts
the sky above your head the same distance away as the horizon, and the
perspective created is not realistic.  Real (cumulus) clouds are only
about 3.5 miles above your head, while the horizon is much further
away if the ground is flat.  Also, it means you can't implement the
fog idea, because the sky above your head gets washed out as much as
the horizon (since it is at the same distance).

So, the way I do it is to use three basic elements:
  1) Blue_Sky3 texture
  2) Parallel planes for ground and sky
  3) Fog at a distance

Consider scaling the Blue_Sky3 texture unevenly when you map it.
This can produce clouds which aren't just puffy, but maybe like the
wind is blowing all the clouds and "stretching" them in one direction
(the kind of clouds you see sometimes at the edge of a cold front).
Also consider rotating the sky plane around the Y axis to align the
"wind direction" to whichever direction you want.  This is easier than
figuring exactly what vector to scale the texture on.

I have also included a POV file called POVSKY.POV to illustrate
everything, and uploaded POVSKY.GIF separately.

I hope this lengthy verbiage can be of some use!!


        - Bruce Bacher
e-mail me: bruce.bacher@clcbbs.hou.tx.us
ECHO is on
ECHO is on