Hello,
How can a image map be distorted so it will look right when it is mapped
onto a sphere (like a map of the Earth)?  I am making macros for each
planet and might write a program to build solar systems.
Brendan Ryan

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Andrea Ryan wrote:
> 
> Hello,
> How can a image map be distorted so it will look right when it is mapped
> onto a sphere (like a map of the Earth)?  I am making macros for each
> planet and might write a program to build solar systems.
> Brendan Ryan

 Look up in the Pov docs under map_type. For spherical mapping you need
to use map_type 1. Default is map_type 0 which is planer mapping. It
should be noted that square images have some problem when mapping them
to a sphere especialy at the poles where you start to get "pinching".
I forgot the exact term for it but there are earth images and others
that are especialy designed for this type of application but I do not
know the proceedures for creating them.

 You might want to check out these links for other people's include files
and for planet image maps to give yourself a starting point:

Pov stuff:

http://home.global.co.za/~mvds/software.htm
http://www.digiquill.com/kwansys/povspace.html
http://www.ndirect.co.uk/~chris.dennis/povray.htm

Planetary and star maps:

http://samadhi.jpl.nasa.gov/maps/
http://home.HiWAAY.net/~nholmes/planets/
http://seds.lpl.arizona.edu/billa/twn/top.html
http://www.radcyberzine.com/xglobe/index.html#maps
ftp://adc.gsfc.nasa.gov/pub/adc/archives/catalogs/
http://www.lancs.ac.uk/postgrad/thomasc1/render/maps.htm




-- 
Ken Tyler -  1200+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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You may have to use planar, cylindrical or spherical mapping (see docs about
map_type). The choice depends on the projection type of the map you have. If the
map uses the equal-area cylindrical projection, use cylindrical mapping to apply
it to he sphere. If the map uses the equidistant cylindrical projection (aka
rectangular or equirectangular), use spherical mapping. If you happen to have
two orthographic projection maps of opposing hemispheres, you can use planar
mapping.
AFAICS you cannot use any other projection type, although some can be converted
to a suitable type.

For information about map projections, see for example:
http://www.ahand.unicamp.br/~furuti/ST/Cart/Dither/CartHow/cartHow.html

Margus

Andrea Ryan wrote:
> 
> Hello,
> How can a image map be distorted so it will look right when it is mapped
> onto a sphere (like a map of the Earth)?  I am making macros for each
> planet and might write a program to build solar systems.
> Brendan Ryan

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Ken <tyl### [at] pacbellnet> wrote:
:  Look up in the Pov docs under map_type. For spherical mapping you need
: to use map_type 1.

  Note also that your sphere must be centered at the origin before mapping,
or else...

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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Nieminen Juha wrote:
> 
> Ken <tyl### [at] pacbellnet> wrote:
> :  Look up in the Pov docs under map_type. For spherical mapping you need
> : to use map_type 1.
> 
>   Note also that your sphere must be centered at the origin before mapping,
> or else...

I should have mentioned the image mapping tutorial at -
http://members.xoom.com/yang4yang/pov/imap1.html

-- 
Ken Tyler -  1200+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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