Hello!

I am working on a video project and need the more or less "stock" animation
of a camera in outer space zooming into the earth.  It didn't sound like a
difficult problem so I decided to give Windows Povray 3.6 a try and worked
up my first .POV file:

//============================

#include "colors.inc"

background { color Black }

camera {
  location <0, 0, 300>
  look_at  <0, 0,  0>
}

sphere {

    <0, 1, 2>, 100
    texture
    {
      //pigment { color Yellow }

      pigment{ image_map { tiff "land_ocean_ice_8192.tif" map_type 1 } }

      //pigment{ image_map { tga "land_ocean_ice_8192.tga" map_type 1 } }

      finish { ambient 0.6  phong 0.3 diffuse 1 }
    }
    rotate y*230 rotate x*23.45
}

light_source { <0, 150, 150> color White}

//=================================

For the image map, it comes from NASA's blue marble website:

http://visibleearth.nasa.gov/images/2430/land_ocean_ice_8192.tif


Problem:

1) When I render the picture, the image is almost completely black.  It
appears POVRAY doesn't work with .TIF files with alpha channels?

2) So I load Photoshop 7.0 and convert the image to a .PNG file with an
alpha channel.  Still doesn't work.

So I convert the image to a .TGA file and it renders correctly, except I was
trying to use the alpha channel to properly render specularity:

a. render a globe of the earth with full specularity
b. render a slightly larger sphere with no specularity but with the alpha
allowing the oceans to shine through
c. add some cloud layers, etc.

Converting to an indexed color format is not a good solution to me as the
color banding when the video is processed by my mpeg encoder makes the
image rather useless.

Is there something special about using images with alpha channels?  Is there
a bug with POVRAY and handling .TGA / .PNG files with alpha channels?

Thanks for any help you can give me.  What sounds like a simple job has
turned out to be a severe annoyance.

Aloha!!!!!

Tim Otholt

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