Clive,
My understanding is that positions and orientations are recorded in Cel:// URLs as floating point numbers. I was writing about the "gibberish" letter combinations, which are dumps of most, but not all, of Celestia's state flags.
stars.dat : star coordinates
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chris
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selden wrote:Clive,
My understanding is that positions and orientations are recorded in Cel:// URLs as floating point numbers. I was writing about the "gibberish" letter combinations, which are dumps of most, but not all, of Celestia's state flags.
Orientations are recorded as floating point numbers, but positions are not. Neither of the standard IEEE 754 floating point types--32-bit single precision and 64-bit double precision--are sufficient to represent positions throughout the universe to the precision required by Celestia. Instead, Celestia uses it's own 128-bit fixed point numbers for coordinates. In a cel:// URL, the bits appear in the standard base64 encoding where the characters A-Z are digits 0-25, a-f are digits 26-51, 0-9 are digits 52-61, + is 62, and / is 63.
--Chris
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cpotting
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chris wrote:Orientations are recorded as floating point numbers, but positions are not. Neither of the standard IEEE 754 floating point types--32-bit single precision and 64-bit double precision--are sufficient to represent positions throughout the universe to the precision required by Celestia. Instead, Celestia uses it's own 128-bit fixed point numbers for coordinates. In a cel:// URL, the bits appear in the standard base64 encoding where the characters A-Z are digits 0-25, a-f are digits 26-51, 0-9 are digits 52-61, + is 62, and / is 63.
--Chris
Thanks Chris. I'll have to tuck that bit of knowledge away. It may come in handy sometime when writing a script.
Clive Pottinger
Victoria, BC Canada
Victoria, BC Canada