My friend is preparing an astronomy lecture and asked me to produce a video 
of a saturn flyby, so I dusted of an old saturn I did, but I wasn't 
satisfied with the rings.

The original version used a spherical pattern and a colour_map to do the 
rings, but it looked flat and artificial.

Here is the latest version. The new version uses three images from Bjorn 
Jonsson's excellent website (http://www.mmedia.is/~bjj/) for the rings. The 
problem I had was that POV has no innate way of mapping an image_map 
radially onto a flat plane (ie the rings). I solved this by writing some 
functions that map a radial coordinate onto the linear image_map. The new 
rings show far more detail and look much more realistic. If anyone knows an 
easier way please tell me!

I have posted the source and image files into p.b.s-f

Now the animation is done, my friend has asked if I can do another of 
Jupiter!

Rarius

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Attachments:
Download 'Saturn.png' (237 KB)

Preview of image 'Saturn.png'

Am 14.04.2010 01:10, schrieb Rarius:

> Here is the latest version. The new version uses three images from Bjorn
> Jonsson's excellent website (http://www.mmedia.is/~bjj/) for the rings. The
> problem I had was that POV has no innate way of mapping an image_map
> radially onto a flat plane (ie the rings). I solved this by writing some
> functions that map a radial coordinate onto the linear image_map. The new
> rings show far more detail and look much more realistic. If anyone knows an
> easier way please tell me!

Using an image map with cylindrical warp should do the job, but you'll 
have to rotate (and possibly translate and scale) the image map in a 
suitable fashion first:

     pigment {
       image_map { png "foobar.png" }
       rotate <0,90,90>
       warp { cylindrical }
     }

This assumes that the image map shows the rings as vertical stripes, 
each representing a full 360 degrees arc.

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"clipka" <ano### [at] anonymousorg> wrote in message 
news:4bc58455$1@news.povray.org...
> Using an image map with cylindrical warp should do the job, but you'll 
> have to rotate (and possibly translate and scale) the image map in a 
> suitable fashion first:
>
>     pigment {
>       image_map { png "foobar.png" }
>       rotate <0,90,90>
>       warp { cylindrical }
>     }
>
> This assumes that the image map shows the rings as vertical stripes, each 
> representing a full 360 degrees arc.

Many thanks for that clipka. I thought a warp might do it, but I just 
couldn't find anything in the documentation about how warp{cylindrical} 
worked and/or the parameters.

Your assumption is correct. the images are vertical bars...  Now all I need 
to do is figure out how to combine the three images I have, colour, 
transparency and albedo together!

Rarius

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Am 14.04.2010 11:44, schrieb Rarius:

> Your assumption is correct. the images are vertical bars...  Now all I need
> to do is figure out how to combine the three images I have, colour,
> transparency and albedo together!

I'd try as follows:

- Use the colour file as a pigment image_map to get your hue.

- Use the albedo file as a texture image_pattern to mix between plain 
black and the hue pigment.

- Use the transparency file as a texture image_pattern to mix between 
transparent (rgbt 1) and that other mixed texture.

Or use some image processing software (Photoshop or Gimp or whatever you 
have) to do the mixing into a .png with alpha channel, and use that 
straight away as a pigment image_map.

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