Geometry Boost List: Re: [geometry] 3D box -> 3D multi_polygon conversion

Subject: Re: [geometry] 3D box -> 3D multi_polygon conversion
From: Barend Gehrels (barend_at_[hidden])
Date: 2013-06-11 15:25:36

Hi Tomislav,

On 11-6-2013 21:13, Tomislav Maric wrote:
> Thank you Barend.
>
> I'll dig around and try to see what I need to do to get things running
> for 3D. Any suggestions regarding where should I start and what needs to
> be done?

A lot needs to be done there...

Note that converting a box to e.g. a ring is not that simple. A 3D box 
has two z-coordinates, which cannot be just converted into a ring with 
height, you will loose one coordinate. Unless you define a ring with two 
z-coordinates (ground and height), which is basically possible, but that 
will make the conversion less generic.

What is basically implemented for 3D is, out of my head:
- the concepts are dimension-agnostic, so for example get/set
- some dimension-agnostic algorithms (of course) as num_points, 
num_geometries, reverse, unique, for_each
- distance (3D points or actually N-D points)
- centroid (idem) for point collections
- derived from distance: length (3d segments or linestrings, or n-d) / 
perimeter
- derived from distance: simplify
- conversion to WKT/DSV
- some in details are basically N-D but never tested as such, or will 
only work with (probably minor) fixes, such as sectionalize

What we need is a polyhedron, and then operations on it, which will be a 
major work on itself.

Bruno has certainly more ideas about this.

Regards, Barend