Thanks to a discussion in povray.advanced-users, someone mentioned an SCurve
function that matches up the second derivatives much better. I've
implemented this as a noise_generator option (activated by the keyword
"match_second_derivatives"). The result is certainly an improvement. The
grid *is* still visible, partially because the noise function is based on a
grid of values, and partially because the 3rd, etc derivatives still don't
match up.

The attached version shows each noise generator (4 is my 4D noise generator
with slice set to 0.5) used as a normal pattern on a sphere. Note that these
have the fix_shadow_line flag on (described in an earlier post to this
group, see "My recent work").

The fixed version rendered slower, of course, but it will be useful in the
occasional instance where unturbulated noise is used for isosurface
displacement or for normals.

 - Slime
[ http://www.slimeland.com/ ]

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