Hi Carsten,

On Tue, May 5, 2009 at 6:29 PM, Carsten Neumann <[email protected]> wrote:
> Ákos Balázs wrote:
>> the exactinit() stuff is only used by the tessellator so it shouldn't
>> matter too much. But since it's been there for quite a while (AFAIK
>> Carsten ported the NURBS-stuff to OpenSG2 sometime end of last year) I
>>  wonder why noone was hit by this before.
> hm, 64 bit windows still seems to be quite rare...

Well, I use it daily. Plus it was also present in the 1.x tree I think...

>> I also wonder then how can
>> you set your fp precision preferences in 64 bit mode. :)
> it seems on windows the answer is "you can not", at least that is how I
> read:
> <http://msdn.microsoft.com/en-us/library/c9676k6h(VS.80).aspx>

Yeah, Gerrit pasted this above aswell but I'd find it rather strange
if this really was the case.

> Ákos, can you share a bit information about the impact of this for the
> NURBS tesselator? How important is it that it can control the use of
> excess floating point precision?

The code is actually taken from the GTS project (with permission) and
only used for the robust predicates stuff (2D incircle / orientation
tests). It will work without this, but the math behind will obviously
be less robust. It's hard to say how much as it completely depends on
the "niceness" of the NURBS data feeded to the tessellator. If the
data comes from e.g. a CAD source with a bad exporter it can be a
problem, but usually for most datasets it's not. We had a couple
models back in Bonn where we really needed this, but some of our
models had really problematic parts. I will take a look how GTS
handles this. So all in all, I'd say it's "nice to have" but not
critical.

HTH,

        Ákos

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