Geometry Boost List: [geometry] distance between geometries

Subject: [geometry] distance between geometries
From: Adam Wulkiewicz (adam.wulkiewicz_at_[hidden])
Date: 2013-09-01 09:36:37

Hi,

I'd like to expose some functionalities that are currently in 
index::detail to the user, the algorithms calculating:
- the shortest and longest comparable distance,
- the comparable distance on a path (linestring or segment) to the first 
intersected geometry from the first path's point or even from some 
intermediate position on the path.

I'd like to expose them to allow users passing a strategy to nearest() 
predicate. The user would be able to define how the distance is 
calculated. The same predicate would work as knn queries (1) or ray 
queries (2).

The use case would e.g. look like this:

1. return 5 buildings (Box) nearest to the river (LineString)

tree.query(nearest(river, 5, shortest_distance), out_it);

2. return 5 bridges (Box) nearest to the begin point(or current 
location) along the river (LineString) to the north.

tree.query(nearest(river, 5, path_distance), out_it);
tree.query(nearest(river, 5, path_distance(location)), out_it); // maybe

The user would also be able to use the distance to the Geometry related 
to the stored bounding box, not only the distance to the bounding box.

Do you think that they're good candidates not only for the BGI but also 
for the entire BG? In other words should they be implemented in the 
boost::geometry or boost::geometry::index namespace? Also do you have an 
idea for the name? Currently I'm using comparable_distance_near() and 
comparable_distance_far(). Should they have separate names or e.g. be 
implemented as bg::comparable_distance with strategy (probably empty)?

Regards,
Adam