Am 24.04.2016 um 17:36 schrieb Le_Forgeron:

> Now thinking about it: what is the gain of one function being the sum of bounded
boxed functions,
> compared to a multitude of distinct functions which are bounded by their own box ?
> 
> Wouldn't it duplicate the union{} for isosurfaces ?

Not at all.

Just think of blobs: As far as the underlying maths goes, a blob is just
a special kind of isosurface, and its underlying function is indeed the
sum of multiple component functions, each of which have a limited volume
of influence, and the algorithm makes use of bounding; so in a blob you
have exactly the situation in question.

Now note that a blob comprised of a single element (and thus a single
component function) is spherical in shape. If you'd union{} multiple
such single-element blobs together, you'd get a boring set of (possibly
overlapping) spheres -- an entirely different shape than if you add the
components up together in a single blob.

The difference is that if you use a union, you're combining the results
of a threshold operation applied to individual elements, whereas in a
blob (and also in a isosurface based on a sum of functions) you're
applying a threshold operation to a combination of those elements.

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