Wasn't it Simen Kvaal who wrote:
>Mike Williams wrote:
>>The problem is related to the fact that you have lied about the
>>max_gradient value, and Megapov has trusted your value. If you replace
>>the line "max_gradient 20" by "eval" (and render a very small image,
>>otherwise it takes forever) then Megapov will calculate the true
>>max_gradient and log it in the statistics output.
>>
>Using the suggested solution by Gilles Tran, simply by adding method 1, the
>scene renders perfectly in both cases. I understand what you say about
>max_gradient and such, but my experience with isosurfaces (and unofficial
>patches in general) is to never expect the expected.

Aha. What threw me was that the help files that I've got clearly state
that method 1 is the default. It looks like what's happening is that if
you use the syntax  "function {foo(x,y,z)}" the method is defaulting to
2, but if you use "function {<expression>}" the method defaults to 1.
When using method 2 you must give it a correct max_gradient.
                    
I observe that explicitly specifying "method 2" in your first example
causes it to fail in the same way as your second example was doing. So
that supports my contention that it was defaulting to method 1, and the
second example was defaulting to method 2.

I reckon that the way it's defaulting is a bug, and it's what's been
causing much of the unexpected behaviour from isosurfaces.

-- 
Mike Williams * ##
Gentleman of Leisure

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