Re: [boost] Geometry and spatial indexes, my opinion

Subject: Re: [boost] Geometry and spatial indexes, my opinion
From: Matthias Schabel (boost_at_[hidden])
Date: 2008-10-09 16:53:26

>> be a teomporary at the interface because as I've just discussed with
>> Brandon, there is the clear need to make things like polar points
>> conform to Cartesian interfaces, which is incompatible with direct
>> access to the data members.  Since we already have to make a  
>> temporary
>> we should cast at that point instead of having yet another temoporary
>> and cast later on.
>>
>
> Maybe I'm misunderstanding something, but it seems to me that an  
> algorithm that works
> with Cartesian coordinates will tend to be very inefficient if it  
> has to convert
> to and from polar coordinates on the fly at every access.

Just to further this point : if we want to do geometry in spherical  
coordinates, then the
point type cannot be homogeneous, especially if we wanted, e.g., to  
enforce dimensional
correctness a la Boost.Units :

cartesianPoint<si::length,si::length,si::length>

vs.

sphericalPoint<si::length,si::radians,si::radians>

I understand that for most of the applications that people are  
considering, cartesian
coordinates are dominant, but I can easily imagine a really cool game  
that accurately
modeled relativistic effects to simulate space combat at near-light  
speed; to do that,
you need a much more sophisticated and flexible system that is capable  
of dealing
with Minkowski metrics rather than Euclidean... You could also have a  
game where players
were constrained to motion on the surface of a 3-sphere...seems like  
there are a bunch
of possibilities that thinking in a cartesian straitjacket precludes.

Matthias