Your HTML (or RTF) posting won't get as much attention, plain text is the
rule here.

I can only offer some feedback.  You were transforming a spherical map, you
did realize that?  It distorts the image terribly when a map meant to go
onto a sphere, such as the sky_sphere, is translated and scaled.  By doing
both you were effectively moving pixels around in odd ways.  Or maybe that
was your intent.

Looking again here at some image maps of both photos and graphics used in a
sky_sphere with either planar or spherical mapping I cannot see what you are
trying to describe.  Except that distortions do occur if used in
unconventional ways.

Using the new spherical lens camera is the only way to perfectly view a
sky_sphere I think.

Bob H.

"David Wallace" <dar### [at] earthlinknet> wrote in message
news:3BB9E6B5.83191D53@earthlink.net...
This may well be a very old issue, but it bears repeating...
I can't get good quality sky_spheres using image_maps.  If I scale them so
that they repeat, I get a mirror effect if I look at certain angles (camera
{ location < -945,287.0 ,  184> look_at <  400, 58.6 ,  0.0> }).  I tried
several translations to fix this; all proved futile.
If I use map_type 1, the effect is very blotchy.  I even made a 4x4 tile of
the original image in another program and combined that with interpolate 2
in the image_map:
sky_sphere {
 pigment {
  #if (IsTest)
   rgb <0.1, 0.3, 0.8>
  #else
   image_map { png "sky6a.png" map_type 1 interpolate 2 }
   translate <0, -1, -1>
   scale .2
  #end
 }
}
The result was still unsatisfactory.  Try it with a 960x960 png (smaller
images show the problem even more) at 1280x1024.  Lowering the render
resolution actually improves the sky_sphere, but at an obvious cost.
The map_type 1 option in image_map ignores all other transformations.  The
problems I have had with it have led me to openly question this decision.
Simply allowing the frequency keyword here would save a lot of trouble.
'interpolate 2' can only do so much, usually around the edges of the pixel
blocks.
There are some who would call this a feature limitation and therefore beyond
the scope of beta-test issues.  But if a limit on a feature makes that
feature unsuitable for its intended purpose, the 'limit' becomes a 'bug',
IMHO.

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