Marc-Hendrik Bremer wrote:
> 
> But a bigger container can require a higher max_gradient (see p.b.b-t
> "isosurface contained_by or evaluation problem"). I'm not sure if this is an
> expectable behaviour, but it seems somewhat logical to me. I finally found
> the description of the isosurface search method from R. Suzuki in p.general:
> RE: Isosurface and function pattern in v3.5
> (Message-ID<3b984214@news.povray.org> if that helps anything). If the points
> d1 and d2 he mentions are further apart, isn't a greater max_gradient
> needed?

No. The gradient of a function is a local property:  <df/dx, df/dy,
df/dz>  The max_gradient value is used to determine if there's a possible
intersection between two points (of arbitrary distance) under the
condition that the gradient between the two evaluated points is maximum.

> But that's all just guessing of course. But it's clear that if the container
> is to big (for what reason ever), the surface will sometimes (but
> reproducible - no "random-number-thingie" as with those pigment-patterns)
> disappear unless you raise max_gradient.

Because of the things mentioned above changing the container size should
have no influence in whether a surface is visible or not (onless you use
'evaluate' of course) but the scene you mentioned really seems to prove
the opposite.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/

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