"Severi Salminen" <sev### [at] NOT_THISsibafi> wrote in message
news:40260cf3$1@news.povray.org...
> I'm trying to model a simple glass bottle. SOR would be a fine way to do
it

lathe is actually better for bottles because sor is only a singular surface
which can't wrap in on itself.

> but I get some odd artifacts whenever I add STURM keyword (see the scene
> below). So can STURM cause these black specks or is it a result of some
> other thing?

I'd say it is due to sturm, yes. Exactly why it happens, I couldn't tell
you. Adding more points usually helps. That Sturmian root solver can clean
up the surface when the camera is parallel to sor (not above or below) or if
there are troublesome point placements.

There has been plenty discussed (and changed?) about it in the past,
ultimately I'm not sure if a 100% perfect solution can exist to prevent
speckling in every instance. However, it is rather interesting that such a
basic shape can be so mangled by the addition of sturm. Perhaps someone with
experience about that bit of program code knows the details concerning this
behavior; whether right or wrong or simply unavoidable unless the code is
changed? Chances are there's a lot of talk about it to be found too, I just
don't remember the last time it was an issue.

Bob H.

> global_settings{ max_trace_level 50 }
>
> camera {
>         location <5,45,-20>
>         look_at <0,15,0>
> }
>
> light_source { <30,50,-50> 1 }
>
> plane{ y,-10
>         pigment { checker rgb 1 rgb 0 scale 10 }
> }
>
> sor {
>      6, <5,-1>, <5,0>, <4.5,16>, <1.5,22>, <1.5,30>, <1.5,31>
>      sturm
>      pigment { rgbf 1 }
>      interior { ior 1.5 }
> }

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