Boost logo

Geometry :

Subject: [ggl] space partitioning
From: Barend Gehrels (barend.gehrels)
Date: 2011-01-12 09:51:17

Hi Adam,

> First of all I'd like to appologize for my absence on the list. I'd like
> to return to the discussion about the spacial index.

Welcome back!

> 1. I'd like to talk about Lucanus' idea that it should be possible to
> build the index on the set-like container providing only keys calculated
> as an indexes on some space-filling curve.
> The base container should be a multimap or multiset but then the
> elements should implement some key concept. The space or some subspace
> should be divided for cells which has equal sizes. And the cells'
> z-curve indexes should be taken as keys.
> The coordinates shouldn't be just transformed into z-curve indexes
> (smallest possible cells). If the precission were too big the structure
> would grow and it would kill the searching process. The same big
> volumetric objects may be present in different cells.
> User should just pick suitable cell's dimensions.
> The resulting container is some kind of sparse, n-dimensional, self
> balancing regular grid.
> What do you think?

Basically it sounds good but it does not yet give me a concrete idea of
how to use it.
Can you give an example?

> 2. Mateusz have you been working on the Federico's quad tree? I have
> version sent by you in 10.09.2010.
> Btw. it could be generalized for n-dimensions.
> 3. Currently I'm becoming acquainted with boost::geometry and I've
> notticed
> struct access<point<CoordinateType, DimensionCount, CoordinateSystem>,
> Dimension>
> I think that Dimension parameter name may be confusing. It might be
> something like DimensionIndex or even better CoordinateIndex.

access is a traits metafunction, so I think there will not be many
Though DimensionIndex is also good. CoordinateIndex does not correspond
with DimensionCount...

Anyway, if you specialize traits, you may name these parameters
yourselves, and I can imagine that, for example, for spherical or polar
systems you might pick another name.

Regards, Barend

Geometry list run by mateusz at