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

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Well, I think there's nothing to do here. If you apply all the cross
products with your right hand, you can still get all the right results
if you use the right vectors. There's nothing to change here.

On Thu, Apr 1, 2010 at 12:59 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.
> 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

Rohit Garg

Senior Undergraduate
Department of Physics
Indian Institute of Technology

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