Marc-Hendrik Bremer wrote:
> 
> [...]
> 
> Of course I have limited experience, but the problem seems not that big as
> it first appears. There is that adaptive gradient method R. Suzuki mentioned
> once (where? Don't know - had something to do with the old "eval" IIRC.) and
> functions like min(min(abs(x),abs(y)),abs(z))) work quite well with there
> infinite gradient and even with low max_gradient settings.

This function does not have an infinite gradient, it should render
perfectly with max_gradient 2.  However it does have non-continuous
derivatives, but this is no problem for isosurfaces.  

> There are problems with the gradient of course and using pigments or
> functions in isosurfaces will sometimes need some high max_gradient
> settings. But I use them all the time and I had no problems, I could not
> solve with some decent settings - even with the really 'evil' brick-pattern,
> which is hard to use in isosurfaces.
> 
> Perhaps your experience is different, but IMHO pattern/pigment-functions are
> very suitable esp. for isosurface beginners.

Pigment and pattern functions are generally suited for isosurfaces as long
as they are continuous.  brick, checker, cells, etc. are not.  You may
have successfully used them,  but every time you change the geometry or
the viewpoint there can be artefacts occuring and it will be unnecessarily
slow so i can only advise against it.

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 21 Feb. 2002 _____./\/^>_*_<^\/\.______

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