Re: [eigen] southern hemisphere support in the Geometry module?

On Thu, Apr 1, 2010 at 3:20 PM, Manuel Yguel <manuel..yguel@xxxxxxxxx> wrote:

In the north hemisphere we tend to overlook the people of the south
one and it is very important that we correct that attitude.
In the same spirit we can propose a patch for the left-handed people.

We definitely don't want to leave out "one out nine Americans" (Flanders, 1989), and a probably similar statistical figure for the other remaining _continents_

Flanders, Ned (1989) http://movie.subtitlr.com/subtitle/show/123788#line101

I have remarked that they tend to prefer undirect reference frames.
We can detect it also at run time by looking at the way the left and
right button of the mouse are binded.

Eigen should definitely be south-hemisphere and left-handed friendly.
I strongly support that move.

- Manuel

On Thu, Apr 1, 2010 at 2:59 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
> Hi,
>
> At the moment, our Geometry module makes the assumption that direct
> isometries have positive determinant, and indirect isometries have
> negative determinant. In the southern hemisphere it's the opposite ---
> this is the mathematical phenomenon behind the famous Coriolis effect
> which makes cyclones spin counter clockwise in the northern
> hemisphere, and clockwise in the southern hemisphere.
>
> http://en.wikipedia.org/wiki/Coriolis_effect
> http://en.wikipedia.org/wiki/Cyclone
>
> I'm working on a patch at the moment but I'm not sure how to best
> implement hemisphere detection. It could be selected at compile-time,
> but that means that binaries can only work in one hemisphere. Or we
> could implement runtime hemisphere detection on platforms that support
> it (more and more devices have accelerometers that detect very well
> the coriolis effect) or just use an internet-based service for
> geolocation, but i'm not sure if it's reasonable to let Eigen depend
> on a HTTP library? We could make that an optional dependency though.
>
> Cheers,
> Benoit
>
>
>