[GRASS5] anyone use/need fragstats?

[John Gillette]

Radim,
I have a question about:

> v.patch input=a,b output=c1
> v.clean input=c1 output=c2 tool=break,rmdupl

Given:                 ___
  _________           |   |
 |         |          |   |
 | A       |          |   |
 |_________|          | B |
                      |   |
                      |___|

patch A,B gives:
        ___
     __|___|__
    |  |   |  |
    | A|   |  |    ?
    |__|___|__|
       | B |
       |___|

There are 4 intersections and 5 areas created
by the patch operation in this example. What does
"v.clean input=c1 output=c2 tool=break,rmdupl"
do to patch's result?

I am interested in a v.mapcalc that would do A union B,
A intersection B, A-B, B-A, as well as Booleans like
is_simple(A), is_convex(A).  Are there library functions
for doing such things in 5.1? I suspect that we are not 
quite there yet? 

Actually, I am more interested in having the library functions
than having v.mapcalc.

Could you tell me what you are working on with respect 
to these kinds of problems and what your plans are?

Ref: general polygon clipper library (gpc)
     http://www.cs.man.ac.uk/aig/staff/alan/software/index.html

     CGAL, the Computational Geometry Algorithms Library
     CGAL Basic Library Manuals, Polygon Operations
     http://www.cgal.org/Manual/doc_html/index.html

John