[Gllug] Faster maths?

[salsaman]

salsaman wrote:

> Adrian McMenamin wrote:
>
>> On Fri, 2007-03-09 at 00:49 +0100, salsaman wrote:
>>  
>>
>>> Adrian McMenamin wrote:
>>>   
>>
>>
>>  
>>
>>> Perhaps you could do some optimising while the index is being 
>>> created ? How do you generate the 8 bit palette ?
>>>
>>>   
>>
>>
>> Median cut
>>
>>  
>>
>
> I'm not familiar with that method, but it appears you will make cubes 
> in RGB space which contain equal numbers of colour pixels.
>
> When you are counting the pixels, then you know which box they belong in.
>
> Or am I missing something ?
>
> Gabriel.
>


OK, now I see where the problem lies; when you add the dithering, each 
pixel moves a random amount.

To calculate this quickly, you should make a 3d map of all the cubes: 
each cube has 6 faces which connect to another cube. So you need an 
array of 256*6 connections. You will also store the side length of each 
cube (256*3 array).

Now when a point moves, you can track it's position as it crosses from 
one cube into the next, first in the R direction, then G, then B. You 
will then know which cube it ends up in, and you can map it to your 
indexed palette.

Gabriel.

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