Am 07.01.2019 um 08:49 schrieb Thomas de Groot:
> On 7-1-2019 8:40, Thomas de Groot wrote:
>>
>> Interesting. I missed that too. Going to play right now as I am 
>> working on an isosurface...
>>
> 
> Hmmm... right. Not what I expected. Polarity may be only relevant if the 
> contained_by shape is close to the isosurface one, i.e. spheres, 
> cylinders, cubes. Otherwise, I don't understand its usefulness. Polarity 
> on just renders the contained_by shape, whatever its (positive) value.
> 
> Did I miss something? Probably.

The magnitude of the `polarity` paramezer is irrelevant, only the sign 
matters (or, more precisely, whether the parameter is positive; zero has 
the same effect as a negative value).

`polarity 1` should have the same effect as flipping the signs of both 
the function and the threshold.

If your isosurface is fully inside the `contained_by` shpe, then it is 
perfectly normal that `polarity 1` will cause you to see only the 
`contained_by` shape, because everything outside the `contained_by` 
shape is always considered "outside" (*), while inside that shape the 
"inside" and "outside" are now the other way round.

To just flip "inside" and "outside" (including the space outside the 
`contained_by` shape, you should use the `inverse` keyword instead.


The `polarity` keyword is primarily intended to complement the 
`potential` pattern feature, which would behave inconsistently between 
blobs and isosurfaces unless positive polarity mode is used for the latter.

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