minzi0815 nous illumina en ce 2008-05-28 02:12 -->
> Warp <war### [at] tagpovrayorg> wrote:
>> minzi0815 <mar### [at] eumetsatint> wrote:
>>> So than means, the 65535 possible values are scaled to 256 colors ?
>>   No, it means that you can only specify up to 256 entries in a color map.
>> Colors are interpolated between these entries and thus the total amount of
>> colors generated is limitless (well, limited by floating point range).
>>
>> --
>>                                                           - Warp
> 
> Well, to be honest, I am getting a little cobfused.
> The question for me is the following:
> 
> I want to display a df3 - file that holds 16 Bit measuring values that range
> from 0 to 65535. I want povray to display each value in a different color. How
> is that possible to do ? Do I need a color map at all ?
> 
> 
The simplest color_map possible (color_map[0 rgb 1][1 rgb 0]) actualy have an 
"infinite" number of distinct values. That is, every real values comprised 
between 0 and 1. This number is reduced in a computer by the limitation of the 
binary floating point encoding, but still largely bigger than 65535.

-- 
Alain
-------------------------------------------------
When confronted by a difficult problem you can solve it more easily by reducing 
it to the question, "How would the Lone Ranger handle this?"

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Alain wrote:
> minzi0815 nous illumina en ce 2008-05-28 02:12 -->
> 
>> Warp <war### [at] tagpovrayorg> wrote:
>>
>>> minzi0815 <mar### [at] eumetsatint> wrote:
>>>
>>>> So than means, the 65535 possible values are scaled to 256 colors ?
>>>
>>>   No, it means that you can only specify up to 256 entries in a color 
>>> map.
>>> Colors are interpolated between these entries and thus the total 
>>> amount of
>>> colors generated is limitless (well, limited by floating point range).
>>>
>>> -- 
>>>                                                           - Warp
>>
>>
>> Well, to be honest, I am getting a little cobfused.
>> The question for me is the following:
>>
>> I want to display a df3 - file that holds 16 Bit measuring values that 
>> range
>> from 0 to 65535. I want povray to display each value in a different 
>> color. How
>> is that possible to do ? Do I need a color map at all ?
>>
>>
> The simplest color_map possible (color_map[0 rgb 1][1 rgb 0]) actualy 
> have an "infinite" number of distinct values. That is, every real values 
> comprised between 0 and 1. This number is reduced in a computer by the 
> limitation of the binary floating point encoding, but still largely 
> bigger than 65535.
> 
But that would give gray values only.  Going linearly from rgb <1, 1, 1> 
to rgb <0, 0, 0> would change the red/green/blue values together 
resulting in gray values throughout.  Infinite gradations 
(theoretically), but still only shades of gray.  To get all possible 
*colors* it would be necessary to change the red/green/blue values 
independently, and that's not a linear change.

      -=- Larry -=-

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Larry Hudson <org### [at] yahoocom> wrote:
> But that would give gray values only.  Going linearly from rgb <1, 1, 1> 
> to rgb <0, 0, 0> would change the red/green/blue values together 
> resulting in gray values throughout.  Infinite gradations 
> (theoretically), but still only shades of gray.  To get all possible 
> *colors* it would be necessary to change the red/green/blue values 
> independently, and that's not a linear change.

  The original poster didn't ask for all possible colors, he just asked
for 65536 colors, and 65536 shades of gray (or red, or whatever) is
exactly that, technically speaking.

<nitpicking>
  Besides, 65536 colors are not "all possible colors" (at least not all
possible colors representable with 24-bit rgb).
</nitpicking>

-- 
                                                          - Warp

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