On 9/24/20 5:42 AM, William F Pokorny wrote:
> I've been working on povr's it_ prefixed, internal turbulence, keywords 
> implementation for patterns which have special turbulence handling. 
> Those patterns are: agate, marble, spiral1, spiral2 and wood.
> 
...

An update. I was aiming at another release of the povr code this past 
weekend. It's been a while.

However, I've been playing over the past days some with the new it_* 
keywords with pattern internal Turbulence() working apart from old style 
turbulence in addition. It's easy enough to duplicate previous behavior, 
but I'm finding what can better be accomplished, with the additional 
it_frequency keyword and split turbulence, disappointing. A little 
better sometimes; a little faster sometimes yes, but...

Also learning more about the limitations of the current patterns.

I was already thinking it_scale, it_offset good ideas for clarity and 
control.I now think the it_frequency I used in all five not really the 
right concept for some patterns. Maybe an it_magnitude instead in some 
cases.

We have the wood pattern(1), where, in the ideal case we are missing an 
inbuilt way to vary the growth ring thickness apart from all other 
turbulence/noise(2). Further, the way only x and y turbulence only are 
used internally (no matter the version) introduces asymmetry in the 
result not ideal for a generic treatment of wood cut from a log.

I thought I was further along than I am. I don't yet know exactly what 
I'm doing with these 5 special patterns. FWIW.

Bill P.

(1) - I looked back at v3.1 and it looks there as if the internal 
turbulence was all that was used for wood and marble. The others still 
seeing two coupled turbulences. So looks like there was some change for 
those two patterns over time.

(2) - Wood rings have in seasonal climates early and late contributions. 
  Would an approach to wood more like the pavement and tiling patterns 
make sense... We can with warps handle most turbulence required 
externally. We're also shaping to a triangle wave which doesn't fit the 
ramp wave of growth rings. Might a simple cylindrical pattern (a single 
0-1 ramp) with turbulence and very detailed map(s) be better in general 
for wood. Unsure at the moment where to push.

(2a) Not done it, but pretty sure we can duplicate the existing wood 
pattern with other functionality.

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