Previous postings:

http://news.povray.org/povray.beta-test.binaries/thread/%3C5da21410%40news.povray.org%3E/

http://news.povray.org/povray.beta-test.binaries/thread/%3C5dab3f55%241%40news.povray.org%3E/

http://news.povray.org/povray.beta-test.binaries/thread/%3C5dbc6985%241%40news.povray.org%3E/

and

http://news.povray.org/povray.beta-test.binaries/thread/%3C5dd8006c%241%40news.povray.org%3E/

As discussed previously, I've added a new wave modifier mode called 
function_interval which works in the -1 to 1 range instead of the usual 
pattern range of 0 to 1. As part of this working to update all the 
existing *_wave modifiers to work in both ranges.

Found with the cubic_wave (does anyone really use it today?) when, eons 
ago, the inversion of negative values was introduced to get continuity 
(non-flipping at) while moving from negative to positive values through 
0.0 the cubic pattern was apparently not updated and the continuity was 
mostly broken for it as can be seen in the upper left of the attached 
image applying it to a gradient x pattern.

I worked to fix this, but then could see no advantage for cubic_wave 
over what we already have with sine_wave. I was going to delete it, but 
have decided for povr, to change the existing cubic wave modifier for 
both ranges into a bump (selection) function of sorts. The result of 
this can be seen in the upper right of the attached image again applying 
it against a gradient x pattern.

Today if we try a pattern with cubic_wave like:

granite cubic_wave frequency 3.3 phase -0.5

and use it as an offset to the y plane in an isosurface, we get the 
lower right results in the attached image. It's something, but it has 
awful continuity and is really useful only for noisy results of one kind 
or another.

In the lower right is the bump function result with runs in nearly 1/3 
the time because it maintains the incoming continuity while providing 
for results much more likely to be useful.

Bill P.

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