"Jan Walzer" <jan### [at] lzernet> wrote in message
news:3d14aa3d$1@news.povray.org...
> have you played with accuracy settings ?
Yes. It's one of the first thing I tried after checking the gradient /
avaluate. The grid is visible from accuracy at accuracy 1e-1, 1e-2, ...,
1e-6. I went no further.