Wasn't it Ger who wrote:
>Mike Williams wrote:
>
>> 
>> The problem with the Z_Step function is that there are points where the
>> gradient is infinite. Since you're not setting max_gradient, POV is
>> using the default value of 1, and you get this warning in the message
>> pane:
>> 
>> Warning: The maximum gradient found was 3000.891, but max_gradient of
>> the isosurface was set to 1.100. The isosurface may contain holes!
>> Adjust max_gradient to get a proper rendering of the isosurface.
>> 
>> The "3000.891" value is just what POV happened to find on that run. If
>> you were to increase the max_gradient to that value, it would take an
>> awfully long time to render and still suggest a higher value.
>> 
>I tried setting it at 1000 but that sorta stopped povray dead in it's tracks
>
>> Isosurfaces that have discontinuous functions will never render well.
>
>I don't see the "discontinous" in the function because for every value of z
>there is a determined value of y. But like I said, the last time I saw math
>was 40+ years ago.

That just makes it "defined" everywhere. It's not "continuous" at
integer values of z because if you approach an integer value from below
you get a different limiting value than if you approach the same point
from above.

As far as POV is concerned it's the infinite value of the gradient at
that point that's the problem. If POV finds a point where the function
value evaluates to "F", then it knows that the function can't be zero
within a distance of F/max_gradient from that point, and can therefore
miss points.

-- 
Mike Williams
Gentleman of Leisure

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