We started with Perlin noise but it wasn't really that good.  POV-Ray 
now uses (I assume still uses) one written by Robert Skinner.

David Buck

On 2018-04-27 9:43 AM, William F Pokorny wrote:
> On 04/26/2018 01:13 PM, Bald Eagle wrote:
>> So, I was just looking around at some pattern functions, and having 
>> played with
>> some Perlin noise in the recent past, thought that I'd read up on it a 
>> bit more
>> - specifically it's exact implementation in code.
>>
>> Does POV-Ray currently use original or improved noise?
>>
>> http://flafla2.github.io/2014/08/09/perlinnoise.html
>>
>>
>> Also, I came across this which touts a doubling of speed:
>> Perhaps someone can test this out and see if POV-Ray can benefit from 
>> this.
>>
>> http://riven8192.blogspot.com/2010/08/calculate-perlinnoise-twice-as-fast.html 
>>
>>
>>
> 
> Quite a long while ago I dug a 'little' into this and by the timing of 
> Perlin's improved version I 'guessed' POV-Ray was probably using the 
> original type, but I never verified it.
> 
> The difference IIRC was moving from a grid based approach to some 
> simplex grid based one so the grid pattern was less visible in 2d 
> applied noise. My initial pondering was along the lines of whether in 3D 
> applications of the noise the simplex grid would still be visible with 
> the right alignments of surface to the new grid.
> 
> In the newsgroups I vaguely recall some folks (Christoph Horman?) 
> commenting in some detail on perlin noise in comparison to POV-Ray's 
> other methods. Perhaps search the newsgroups for more.
> 
> Bill P.
> 
>

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