Re: [boost] Formal Review Request: Generic Geometry Library (GGL).

Subject: Re: [boost] Formal Review Request: Generic Geometry Library (GGL).
From: Barend Gehrels (barend_at_[hidden])
Date: 2009-10-14 03:56:41

Hi Mika,

>
> From the documentation it seems like buffering only works for positive 
> offsets. Is the complement operation erosion also supported? Erosion 
> is important when simplifying structures. It is common practice to 
> first expand and then erode to get rid of minor details in shapes.

The building blocks are there. But it is not implemented. Actually, 
buffering of polygons is also not part of this distribution.

>
> Also, from the documentation it seems like Douglas-Peucker is the only
> available simplification algorithm. Do you have any plans to enlarge
> the set of available algorithms? DP is pretty much the worst algorithm
> we have available.

The Douglas-Peucker is implemented as a strategy, the default strategy, 
for the simplify algorithm. The design supports specifying other 
algorithms there, we could add them or library users could add them. At 
this moment DP is the only one. Most libraries have them as the default 
or the only one, by the way.

>
> Triangulation was not mentioned. However, triangulation is an 
> effective tool for simplifying polygons, once you determine what your 
> simplification criteria are. Do you have any plans to add 
> triangulation as an elementary operation?
Yes, there are plans, but indeed it is not implemented.

All your questions focus on generalization/simplification, it is very 
interesting and, as a GIS-man, I'm sure willing to go further in that 
direction.

Regards, Barend

p.s. John, Vicente, thanks for the questions and clarifications, it 
makes the process very clear.