Hi Rutger,
In GGL, coordinate systems are assigned to points. However, one can compute stuff like length, angle, area, etc., with having only a proper inner product operator, without necessarily attaching that operator to each point. It then becomes easy to project some data in different spaces, and still being able run a quick hull. Think of geometric interpretations of non- coordinate data such as dictionaries, medical images, etc..
So, my question would be: is it that generic to assume that all points have a coordinate system?
We've implemented the hull as an "agnostic" strategy because it is not dependant on coordinate system itself. It is however dependant on two underlying strategies, "side" and "compare". So in cartesian coordinate systems the "side" is implemented differently from how it would be implemented in a spherical coordinate system. Same for compare (spherical compare assumes that the coordinates do not span more than halve of the sphere). So yes, for points we need to know in which coordinate system they are placed, in order to get the calculation strategy. Note that the point-type does not have to have one, but the Point Concept. So using a traits class you can bind a coordinate system to a point type. So if you define a "dictionary coordinate space" where the "side" is probably still as defined as it is now for cartesian in the library (it can just register the same calculation class), you can call the convex hull for it. If that answers your question... Regards, Barend