Re: [boost] [Review] We're halfway through the GGL review

Subject: Re: [boost] [Review] We're halfway through the GGL review
From: Fabio Fracassi (f.fracassi_at_[hidden])
Date: 2009-11-15 09:53:10

Hi all,

here is my review. I followed all the discussions since your first 
preview, because I am interested in a good geometry library.
I liked your initial design and was really impressed by the cooperative 
improvement during the iterations.
But before going into details, I think that GGL should become a part of 
boost, so make this a Yes vote.

> - What is your evaluation of the design?

I think it is clean and easy to follow.
The one exception to this is the way union / intersections are handled, 
which I have not fully understood yet.

I would have expected to be able something along the lines of:

polygon p1 = ...;
polygon p2 = ...;

polygon_set ps1 = make_union(p1, p2);
polygon_set ps2;
intersection(ps1, p2, ps2);

I also don't find it too obvious how the extention to 3d geometries is 
going to work, yet.

> - What is your evaluation of the implementation?

I have only skimmed through it, but it looks quite clean. It is easy to 
find each entity, and see what they are doing.

> - What is your evaluation of the documentation?

On the whole I am very pleased with the documentation, its easy to read 
and reasonably complete.
I have a general problem with doxygen generated docu with regard to 
generic libraries. It not easy to separate the important classes and 
fuctions from the implementation details.
GGL helps with this through Grouping by modules and a overview Page, but 
  it could be even better. I think the Modules should them self be 
further grouped, and the most important should be highlighted. Something 
along the lines of (just examples, no informed reordering):

Modules Page
------------

Entities (?)
   Geometries
   Coordinate Systems (?)

Algorithms (? Functions)
   distance
   union
   ...

Utility / Machinery
   core
   concepts
   traits
   ...

And ideally (but I think that it is not feasible in doxygen) better 
Navigation inside these Groups

> - What is your evaluation of the potential usefulness of the library?

I think it is immensely useful to have this in boost. An example like 
qt_example shows that geometry plays a role even in everyday programming 
and is not specific to any particular (niche) domain. I think it is 
important that we have a common vocabulary which scales form there to 
very complex and involved algorithm.

I would love to have it extended to 3d Geometry (especially 
Polygon/Triangle meshes) but I wouldn't make my vote depend on this.
However I think that 3d should become part of the default distribution 
once it is there.

> - Did you try to use the library?  With what compiler?  Did you have any
> problems?

Compiling some example and playing around with them a bit. No problems 
on OS X 10.6 with gcc 4.2.1

> - How much effort did you put into your evaluation? A glance? A quick
> reading? In-depth study?

As stated above reading the Docu, and all communication on this list 
from the get-go. Glancing at the Implementation, and trying out some 
examples.

> - Are you knowledgeable about the problem domain?

Yes, I work in medical visualisation, and have developed geographical 
tools while studying. I have used CGAL and (unfortunately) ACIS and 
evaluated a few others, so I have a good Idea what a c++ geometry 
library should or should not look like.

Kind regards, and great Work

Fabio Fracassi